insitution - erictags or labels provides uniforms. of. sample records, assists the sampler, and ......

C 'DOCURENT RESUME, I

ED 158 965 SE 024 237

TITLE InoriAnic Analyses in Water Quality Control Programs.Training Manual.'

INSITUTION Officn of Water Program Operations (EPA), Cincinnati,Ohio. National Training and Operational TechnologyCenter.

REPORT NO EPA-430/1-77-013 -

PUB DATE Nov 77NOTE 160p.; For related document, see SE 024 238; Contains.

occasidnallight'type

EDRS PRICE BF-$0.83 HC-Z8.69 Plui Postage.DESCRIPTORS Chemical 'analysis; Inservice Education;

*Instructional Aaterials; *Laboratory Manuals;*Pollution; *Post Secondary Education; QualityControl; Science Education; Teaching Guides; *WaterPollution Control

IDENTIFIERS *Water Treatmentel

ABSTRACTThis dboumentis a lecture/laboratory manual dealing

with the analysis of selected inorganic pollutants. Te manual is aninstructional aid for classroom presentations to those with little orno experience in the field, but having one yolr (cr equivalent) ofcollege level inorganic chemistry and having basc4laboratory skills.Topics include; acidity, alkalinity, hardness, chlorine, totalFhosphorus, fluoride, nitrate and nitrite nitrogen, total andsuspended solids, turbidity and specific conductance, samplehandling, accuracy,.precision and error of data, laboratory safetypractices, and elements of quality assurance programs. (RB)

******************** ***** ********************************** **********Reproductions supplied by EDRS are the'best that ca be made

from the original document.******!********a*********tor*************** ** ** ****************4********

EPA-430/1-77-013

INORGANIC ANALYSES EN WATER QUALITYCONTROL PROGRAMS

PAO TOf v.". Tr.1, 04 0.E,FauEI 04

TRAINING MANUAL

U.S. ENVIRONMENTAL PROTECTION AGFNCY,I)OFFICE OF WATER PROGRAM OPERATI?":,'IS(71

LPA-430/1-77-013 ,

November 1977

INORGANIC ANALYSES IN WATER QUALITY CONTROL PROGRAMS

This course is for chemists and technicians with little or no experiencein inorganic analyses commonly renuired for NPDES permit complianceand in other water quality program c. Applicants should have fundamentalknowledge of inorganic cnemistry rti mantitative analysis. and shouldhave basic laboratory skills incluco use of analytical balances, volumetricglassware and titration assemblies.

After successfully completing the course, the ste&nt will know the generalclasses of methods Hated as approved in the Fade, al Register for anabAisof inorganic pollutants, and will be able to use +Le methods to measureeach parameter selected for the course. He will alto know how to applyquality assurance techniques to hilt work and how to validate his analyticalaccuracy and precision.

_

Tne training includes classroo /itistr.iction. Jtudent performance oflaboratory pror. :urea, and dis ussion of each laboratory assignment andreported resul4t

. .The student will perform tne si procedures for acidity, alkalinity.hardness, chlorine. total tho phorus. fluoride, nitrate and nitrite nitrogen.total and suspended *toilet. bidity...and specific conductance. Other topicsare sample handling, .tompli4nce methodology. accuracy. precisica anderror bf data, and ..rmnits df quality assurance programs.

I'

U. S.. ENVIRONMENTAL PROTECTION AGENCY.Office of Water Program Operations

National Training and Operational Technology Center

MAE

These manuals are'prepared for reference use.of student's enrolledin scheduled training courses of the Office of Water Program Operations.U..S. Environmental Protection Agency.

Due to the limited availability of the manuals it is not appropriateto cite Meth as technical references in bibliographies or other formsof publication.

References to pfroducts and manufacturers are for illustration only;such references-do not imply product endorsement by the Office of 2,',

Water Program Operations. U.S. Environmental Protection Aget:cy.

The reference outlines in this manual have been selected and developed witha goal of providing the student with a fund of the best available currentinformation pertinent to toe Subject matter of the course. Individualinstructors'May provide additional material to cover special aspects oftheir own presentations'.

This manual will tie useful to anyone who has need for information onthe subjects covered. However, it should be understood that tne manualwill have its greatest value as an adjunct to classroom presentaiktas.Tne tonere:at advantages of classroom presentation is in the give-and-takediscussion and exchange of information between and among students cndthe instructional staff.

Constructive suggestions for Improvement in the coverage. content, andformat of the manual are solicited and will be given full consideration.

4

CONTENTS

Title or DescriptionS

Outline Number

San2ple Handling - FieTd through Laboratory 1.

Metnodology for Cnemidal Analysis of Water and Wastewater . 2

Statistics for Chemists 3

Accura.cy-Precision-Errob 4

Elements of Quality Assurarce Progiams 5

Volumetric Analysis of Water Quality 6

Acidity, Alkalinity, pH and Buffers eft

Alkalinity and Relationsnips Among tne Various Types of Alkalinities 8

Determination of Calcium and Magnesium Hardness 9

Chlorine Determinations and Their Interpretation 10

Phosphorus in the Aqueous Environment 11

Control of Interfering Ions in Fluoride Determination; 12

Aminonia, Nitrites and Nitrates' 13

Solids Relations in Polluted Water 14

Turbidity-- 15

Specific Conductance 16

Acidity17

Laboratory Procedure for Alkalinity

Laboratory Procedure for 'Total Hardness 19

Amperonletric Determination of Total Residual Chlorine 20

Use,)f a Spectrophotometer 21

Laboratory Procedure for Total Phosprioree 22

Fluoride Analytical Procedures - SPADNS 23,

Floofide Analytical Procedures,- Electrode 24.

Determination of Nitrate/Nitrite Nitrogen .25

Laborrory Procedure for Total Solids

Laboratory Procedure for Nonfilterable (Suspenddl!) Solids

Calibration and Use of a Turoidimeter (Nephelometer)

Calibration and Us of a Conductivity Meter.

Laboratory SafetylPractices

J

26

, 27

28

29

30

SAMPLE HANDLING - FIELD THROUGH LABORATORY

I P.LANNLNG A SAMPLING PROGRAM

A Factors to Consider:

1, Locating sampling sites

2 Sampling equipMent

3 Type of sample required

,a grabb composite

4 Amotmt of sample required

5 F'requency of collection

6 Preservation measures, if any

B Decisive Criteria

1 Nature of the sample source

2 Stability of constituent(s) to be measured

3 Ultimate use of data

II REPRESENTATIVE SAMPLES

if a sample is to provide meaningful andvalid data about the parent population, itmust be representative of the conditionsexisting in that parent source at thesampling location.

A The container should be rinsed two orthree times with the water to be collected.

B Composit)ng Samples

1 For some sources, a composite ofsamples is made which will representthe average situationsfor stableconstituents. '

2. The nature of the constituent to bedetermined may requ're a series ofseparate samples.

WP. SUR. sg. 6a. 11. 77

C _The equipment used to collect the sampleis an-in inortarst factor to consider,ASTMOTi has a detailed section on varioussampling devices and techniques. .

D Great care must heexercised whencollecting samples in sIddge.or mud areasand near benthic deposits. NO definiteprocedure can be given, but carefuleffort should be made to obt-in a rep-.resentative sample..

III SAMPLE IDENTIFICATION

A /lath sample must ye unmistakablyidentified, prefetably with a tag.,or libel.The required information should be planned

'in advance.

B An information form preprinted on thetags or labels provides uniforms ofsample records, assists the sampler, andhelps entre that vital information willnot be omitted.

C Useful Identification Information includes:

1 sample identity code2 signature of sarhpler3 signature of witness4 description'nf sampling location de-

tailed enough to accommodate repro-ducible sampling. (It'may be moreconvenient to record the details in thefield record book).

5 sampling equipment used6 date of collection7 dole of collection8 typeof.sample (grab or composite)!9 water temperature

10 sampling conditions such as weather,water level, flow rate of source, etc.

11 any preservative additions or teChrittmes1.2 record of any determinalions done in

-._the field13 tYpeof analyses to be done in iaboratory

...

Sample Hand - Field Through Laboratory

IV SAMPLE' CONTAINERS

A Available Materials

1. glass2 plastic

hard rrber .

B Consideritions

1 Nature of the sample - Organicsattack polyethylene.

2 Nature of constituent(s) to be determined- Cations cdfiadsorb rtadily on someplastics and on certain glassware.Metal or aluminum foil cap liners caninterfere with metal analyses.

3 Preservatives to be used - Mineralacids attack some plastics:

Mailing Requirements - Coniaineisshould be large enough 'to.allow extravolume for effects oktemperaturechanges during transit. Ali capsshould be securely in place. Glasscontainers must be protected againstbreakage, 'Styrofoam linings areuseful for protecting glassware.

C' Preliminary Check

Any question of possible interferencesrelated tolhe sample container shouldbe resolved before the study begins. Apreliminary check should be made using

. corresponding sample materials, con-tainers, preservatives and analysis.

D Cleaning s*'---

If new contakners are to be used, prelim-inary cleaning is usually not necessary.

If the sample containers have been used,previously, they should bt carefnllycleaned before-use.

Ther.: are several cleaning methods-available. Choosing the best method in-volves careful consideration of the nature

, of the sample and of the co nstituent(e) tobe determined.

1-2

1 Phosphate detejents should not beused tb clean containers for phosphorus

.-" samples..

2# Traces of dichromate cleaning solutionwill interfere with-metal analyses.

E Storage

Sample containers should be stored andtransported in a manner to assure theirreadiness for use.

SAMPLE PRESERVATION

Every effort should be made to achievethe shortest possible interval betweensample collection and analyses. If theremust be a delay and it is long enough toproduce significant changes in the sample,preservation measures are required.

At best, however, preservation effortscan only retard changes that inevitablycontinue after the sample is removedfrom the parent population.

A Functions

Methods of preservation are relativelylimited. The primary functions of thoseemployed are:

1 to.retard biological action2 to retard precipitation or the hydrolysis

of chemical compounds and complexes3 to reduce volatility of constituents

General Methods

1 pH control - This affects preciPitationof metals, salt formation and caninhibit bacterial action.

2 Chemical Addition - The choice ofchemical depends on the change to becontrolk.d.

Mercur.c chloride is commonly usedas a bacteria/ inhibitor. Dispqsal ofthe mercury-containing samples is aproblem w efforts to find a substitutefoe this ti-nd c ant are underway.

Sample Handling - Field Through Laboratory -

To dispose of'solutions of inorganicmercury salts, a recommendedProcedure is to capture and retain themercury salts as the sulfide at a highpH. Several firms have tentativelyagreed to accept the mercury sulfide forre-processing After preliminary' con-ditions are met.")

3 Refrigeration and Freezing - This isthe best preservatiOU technique avail-able, but it is not applicable to alltypes of samples. It is not always apracticaj technique for field operations.

C Specific Methods it4(The EPA Methods Manual( includes atabl, ummarizing the holding times andpreservation techniques for severalanalytical procedures. This informationalso can be found in the standard refer-ences (1, 2, 3) as part of the presentationof the individual procedures.

VI MVTHODS OF ANALYSIS

Standard reference books of analyticalprocedures to determine the physicaland chemical characteristics of varioustypes of water samples are available.

A ZPA Methoils Manual

The Methods Development and QualityAssurance Research Laboratory of theEnvironmental Protection Agency, haspublished a manual of analytical proceduresto provic' uethodology for toring thequality of at Nation's Wate s and to deter-mine the impact orwaste d charges. Thetalc of this manual is ''Me ds for Chem-cal Ana/yids of Water and Wastes."(2)

For,some procedures, theanal:Ist Isreferred to Standard Methods andior toASTM Standards.

01

B Standard Methods

The American Public Health Association,the American Water Works Associationand the Water Pollution Control Federation

prepare and publish a volume describing _methods of water analysis. These includephysical and chemical procedures. Thetitle of this book is "Standard Methodsfor the Examination of Water and Waste-,water."(3)

C ASTM Standards

The American Society. for Testing andMaterials-publishes an annual "book"cf specifications and methods for testymmaterials. The "book" currently con-sists of 47 parts. The pail applicableto water is a book titled, "Annual Bookof ASTM Standards", Hart 31, Water..

D . Other References

Current literature and other books ofanalytical procedures with related in-formation are Available to the analyst:

/ft Federal Register Methodology

When gathering data for National PollutastDischarge Eliminsilion System or State Certi-fication report purposes, or for compliancewith maximum contaminant levels in drinkingwater, the analyst must consult the Federal .Register for a listing.of approvdd analytical .methodology. There he will be directed topages in the above cited reference books whereacceptable procedures can be found. TheFederal Register also provides information con-cerning the protocol for obtaining approval touse analytical procedures other than those listed.

VII ORDER OF ANALYSES

The it situatlon is to perform allanalys shortly after sample collection.In practical order, this is rarelypossible. The allowable holding timefor preserved samples in the basisfor scheduling analyses.

)1.

Sample Handling - Field Through Laboratory

A The allowable holding time for samplesdepends on the nature of the sample, thestability of the constituent(s) to be de-termined and the conditions of storage.

1 For some constituents and physical...values, immediate determination s

required, e. g. dissolved oxygen, pH. -

2 Using preservation techniques, theholding times for other determinationsrange from 6 hours (SOD) to 7 days(COD). Metals may be held up to 6months.(2)

3 The EPA Methods Manual Wand Standard

-

Methods (3/in elude a table summarizingholding times and preservation techniquesfor several analytic:41 procedures. Thisinformation can also be found in the

standard references (1, 2. 3) an part of thepresentation of the indiOidual procedures.

-4 If dissolved concentrations aresought, filtration should be done inthe field if at all possible. Other-wise, the sample is filtered as soonas it is received in the laboratory.A 0.45 micron membrane filter isrecommended for reproduciblefiltration.

B The time interval between collectionand analysis is important and should berecorded in the laboratory record book.

VIII , RECORD KEEPING

The importance of maintaining a bound,legible record of pertinent informationon samples cannot be over-emphasized.

A Field Operations

A bound notebook should be used. Informa-tion that shoulit be re^orded includes:

1-4

1 Sample identification records (SeePart

2 Any information ...equested by theanalyst as significant

3 _Details of sample preservation

4 A complete record of data on anydeterminations-done in the field.

4 (See B, next)

5 Shipping details and records

B Laboratory Operations

Samples should be logged in as soon asreceived and the analyses performedas soon as possible.

A bound notebook should be used.Preprinted data forms provide uniformityof records and help ensure that requiredinformation will be recorded. Such sheetsshould be permanently bound.

Items in the laboratory potebook wouldinclude:

1 sample identifying code2 date and time of collection3 date and time of analysis4 the analytical method used5 any deviations from the analytical

method used and why this was done6 data ootained during analysit7 results of quality control checks on the

analysis8 any information useful to those who

interpret and useihe data9 signature of the analyst

9

40

se.

IX SUMMARY

Vatic data can be obtained only iron-. a repre-sentative sample, wunistakablycarefully collected and stored. A rkilledanalyst, using approved methods of analysesand performing the determinations withinthe prescribed time limits, cah produce datafor the sample. This data will be of valueonly if a written record exists to verify samplehistory from the field through the labOratory.

REFERENCES

ASTM Annual Book of Standards,Part 31, Water, 1975,

1

2 Methods for Chemical Analysis of Water -

and Wastes, EPA-MMQARL,Cincinnati, OH 45268. 1974,

3 Standard Methods for the Examiriation ofWater and Wastewater,. 14th editionAPHA-AWWA-WPCF, 1976.

a.

Sample Handling Field Through Laboraloa_

Dean, FL., Williams R. and Wise, 11,,Disposal of MerCury Wastes frpm.Wafer kaboratories, EnvironmentalScience and Technology, October, 1971.

This outline .was prepared by.A. D. Kroner,Chemist, National Training and OperationalTechnology Center, MOTD, °APO, USEPA,Cincinnati, Ohio 45268 .

'Descriptors: On-Site Data Collections,On-Site Investigations, Planning,. Handling,Sample. Sampling, Water Sampling, SurfaceWaters, Preservation, Wastewater

0

10

METHODOLOGY FOR CHEMICAL ANALYSIS OF WATER AND WASTEWATER

I INTRO

This outline deals with chemical methods whichare commonly o. rformed in water qualitylaboratories. Although a is.rge number ofconstituents or properties may be of interee,to the analyst. many of the methods employedto measure them are based on the sameanalytical principles. The purpose of thisoutline Is to acquaint you with the principlesinvolved in commonly-used chemical methodsto determine. Water quality.

II PRE-TREATMENTS

For some parameters, a preliminaryetreatmentis required before the analysis begins. These

serveerve *Mous purposes.

A Distillation To Isolate the byheating a portion of the sample mixture toseparate the more volatile part(s). and then

' cooling and condensing the resulting vapor(s)to recover the volatilized portion.

B Extraction - To isolate/concentrate theconstituent by shaking a poPtIon of thesample mixture with an immiscible solventin which the constituent is much moresoluble.

C Filtration - To separate undissolved matterfrom a sample mixture by passing a portionof it through a filter of specified size.'Particles that &re dissolved in the originalmixture are so small that they stay in thetunple solution and pass through the filter.

D Digestion - To change cons ituents to a formamenable \iz the specified test by heating aportion of the sample mixture with chemicals.

III .METERS

For some parameters, meters halm beendesigned to measure that specific constituent

, or property.r

14b. IL 77

11

A pH Meters

pH (hydrogen ion concentration) is meas-ured as a difference in potential i roso aglass membrane which is in contact withthe sample and with a reference solution.The sensor apparatus might be combinedinto one probe or else it is divided into anindicating electrode (for the sample) and areference electrode (for the referencesolution). Before using, the meter mustbe calibrated with a solution of known pH(a buffer) and then checked for properOperation with agIsuffer of a different pH tvalue.

Dissolved Oxygen Meters

Dissolved oxygen meters measure theproduction of a current which is proporticnialto the amount of oxygen gas redubed at acathode in the apparatus. The oxygen gasenters the electrode Ihrough a membrane,and an electrolyte solution or gel acts as atransfer and reaction media. Prior to usethe meter must be calibrated "against a knownoxygen gas concentration.

C Conductivity Meters

Specific conduPaKe is measured with ameter containinera Wheatstone bridge whichmeasures the resistance of the samplesolution to the transmission of an electricCurrent. The meter and cell arcalibratedaccording to the conductance of a standard.solution of pot/Or:um chloride at 25C.

'measured by a "standard" cell with electrodesone cm square spaced one cm apart. Tnisis why results are called "specific" con-ductance.

D Turbidimeters

A turbidirneter compares the intensity oflight scattered by particles in the sanfPleunder defined conditions with the intensityof light scattered by a standard referencesuspension.

2 -1

M....thoaolagy for Chemical Aanlysis of Water and Wastewater?

SPEi 11-W Ii" ELI:i"rttutlEs

Just as the conventional glass electrode .for pit developi an electrical potential inresponse to the activity of hydrogen ionin solution, the specific ion electrodedevelops an electrical potentialin responseto the activity of the ion for -which the electrodeis specific. The potential and activitr. arerelated accordinp to the Nernst equal on.Simple analytical techniques can be appliedto convert activity to an expression of con-centration.

These electrodes are used with a pH meterWith an expanded my scale or with a specificion meter. Two examples are the ammoniaand fluoride electrodes,

A Ammonia

B

The ammonia electrode uses a hydrophobicgas-permeable membrane to separate thesample solution from an ammonium chloride-internal solution. Ammonia in the samplediffuses through the membrane and altersthe pH of the_ internal solution. which is.iensed by a-pH electrode. The constantlevel of chloride in the internal solution Issensed by a chloride selective ion electrode .which acts as the reference electrode.

The fluoride electrode consists of a lanthanumfluoride crystal across which a potential isdeveloped by fluoride ions. The cell may berepresented by Ag/Ag Cl. C1 (0.2),F (0.001)LaF/test solution /SCE /, It is used in con-

e junction with a standard single junctionreference electrode.

V GENERAL ANALYTICAL METHODS

A Volumetric Analysis

Titrations involve using a buret to me isurethe volume of a standard solution of sub-stance required to completely react withthe constituent of interest in a measu"..edvolume of sample. One can then calculatedi, original concentration of the constituentof interest.

There are various ways to detect the endpoint when the reaction is complete.

2-212

1 Color change indicators

The method may utilize an indicator whichchanges color when the reaction iscomplete. For example, in the ChemicalOxygen Demand Test the indicate:I..,ferroin, gives a blue-green color to themixture until the oxidation-reduction -reaction is complete. Then the mixtureis yeddish-brown.

Several of these color-change titrationsmake use of the iodometric processwhereby the constituent of interest quan-titatively releases free iodine. Starchis added to give a blue color until enoughreducing agent (sodium thi&sulfate orphenylarsine oxide) is added to reactwith all the iodine. At this end point,the mixture becomes colorless,

2- Electrical propertylindicators

Another v ay to detect end points is a. change in an electrical property of the

solution when the reaction is complete.In the chlorine titration a cell containingpotassium chloride will produce a smalldirect current as long as free chlorineis'present. Ae a reducing agent (phen-ylarsine oxide) is added to reducethe chlorine, the microamrneter which-measures the existing direct currentregisters a lower reading on a scale.By observing the scale, the end point oftotal reduction of chlorine can bedetermined because the direct currentceases.

3 Specified end points

For acidity and alkalinity titrations, the'end points are specified pH values forthe final' mixture. The pH values arethose existing when common acidity oralkalinity components have been neutral-ized. Thus acipty is determined bytitrating the sample with a standardalkali to pH 8.2 when carbonic acidwould be neutralized to (CO3)', Alka-linity (except for highly acidic samples)is determined by titrating the' samplewith .. standard acid to pH 9:5 when thecarbonate present has been convertedto carbonic acid, pH.meters are used todetect the specified end points.

Methodology for Chemical Analysis of Water and Wastewater

13 Graviraic Procedures

Gravimetric rufthods involve directweighing of the constituent in a container.An empty container is weighed. theconstituent is separated from the samplemixture and isolated Li the container. thenthe container with the constituent is weighed.The difference in the weights of the-containerbefore and after containing the constituentrepresents the weight-of the constituent.

The type of container depends on the methodused to separate the constituent from thesample mixture.. In the solids determinations.the container is an evaporating dish (total ordissolved) or a glass giber filter disc in acrucible (suspended). For oil and grease.the container? a flask containing a residueafter eVapor tion of a solvent.

C' Combustion

orribustion means to add oxygen: InnheTotal Organic Carbon Analysis. combustionis used within an instrument to convertcarbonacehus material to earbon dioxide.An infrared analyzer measures the carbondioxide.

VI PHOTOMETRIC METHODS ,. ,.

These methods involve the measurement of lightthat is absorbed or transmitted quantitativelyeither by the constituent of interest or elsebya substance containing the constituent of interestwhich has resulted from, some treattpept ofthe sample. The quantitative aspect'of thesephotometric methods is based on applying thetambertzBeer Law which established that theamount of light.absorbed is quantitativelyrelated to the concentration of the absorbing

oft medium through w ich themedit.m at a given wavelength and t giventhickness olight passes.

Each method requires preparing a set rf'standard solutions containing known amountsof the constituent of interest. Photometric

are °Alined for the standards. Theseare uselqo draw a calibration (standard) curveby plotting photometric values against theconcentrations. Then, by locating the photo-metric value for the sample on this standardcurve, the unknown concentration in thesample can be determined.

A Atomic Absorption

Atomic Absorption (AM instruments utilizeabsorption of tight of a characteristic wave-length. This form of analysis involvesaspirating solutions of metal ions (cations)or molecules containing metals into aflame where they are-reduced to individualatoms ih a ground electrical state. In thisCondition,. the atoms can absorb radiationof a wavelength characteristic for eachelement. A lamp containing the element ofinterest as the ckthode is used as a sourceto emit the chgracteListic.line spectrum forthe element to be determined.

The amount of energy absorbed is directlyrelated to the concentration of the elementof interest. Thus the Lambert-Beer Lawapplies. Standards can be prepares andtested and the resulting absorbance valuescan be used to construct a calibration

,(staitclard) curve. Then the absorbance-value for the sample is located on this curve

to determine the corresponding concentration.

Once the instrument it adjusted to giveoptimiim readings for the element of interest.

the testing of each solution can be done inamatter of seconds. Many laboratorieswire recorders into their instruments torapidly transcribe the data, thus conservingtimelment on this aspect of the analysis.Atomic absorption techniques are generallyused for metals and semi - metals in solutionor'else solubilized through some form ofsample processing. For mercury. theprinciple is utilized but the absorption oflight occurs in a flameless situation withthe mercury in the vapor state and containedin a closed glass cell.

B Flame Emission

Flame emiesion'photometry ?involvesmeasuring the amount of light given off byatoms drawn into a flame. 1t certaintemperatures, the flame raises the electronsin atoms to a higher energy level. Whenthe electrons fall back tq a lower energylevel, the atoms lose (emit) radiant energywhich can be detected and measured.

Again standards must be prepared andtested to prepare a calibration (standard)curve. Then the transmission value of thesample can be located on the curve todetermine its concentration.,Many atomic absorption instruments can beused for flame emission photometry.

r Sodium and potassiun. are very effectivelydetermined by the emission technique.

12-3

Methodology for. Chemical Analysis of Water and Wastewater

Flow,ever. for many elements. absorptionanalysis is more sensitive because there area great number of unexcited atoms in theflame which are available to absorb, the .

radiant energy.

---C-1Colorimetry

Colorimetric analyses involve treatingstandards which contain known concentrationsof the constituent of interest and also thesample with reagents to produce a enloredsolution. The greater, the concent.r .lion ofthe constituent, the more intense will bethe resulting color.

The Lambert-Beer Levi which relates theabsorption of light to the thickness andconcentration of the absorbing mediumapplies. Accordingly, a spectrophotometeris used to measure the amount of light ofappropriate wavelength which, is absorbedby the same thickness of each solution.The results from the standards are used toconstruct a calibration (stahcrard) curve.Then the absorbance Value for the sampleis located on this curve to determine thecorresponding concentration.

Many of the metals and'several otherparameters (phosphorus. ammonia, nitrate.nitrite. etc.) arc determined in thismanner.

VII GAS-LIQUID CHROMATOGRAPHY

Chromatography techriiques involve a separa-tion of the components in a mixture by usingn difference in the physical properties of thecomponents. Gas-Liquid Chromatography(GLC) involves separation ba9ed on a differ-ence in the properties of volatility and solu-bility. The method is used to determinealgicides, chlorinated organic compoundsand pesticides:

The sample is introduced into an injectorblock which is at a high temperature (e.g.210°C). causing the liquid sample to volatilize.An inert carrier gas transports the samplecomponents through aliquid held in place asa thin film on ar. 'inert solid support materialin a column.Sample components pass through the columnat a speed partly governed by the relativesolubility of each in the stationary. liquid.Thus the least soluble components are thefirth to reach the detector. The type ofdetector used dependeon the 'class of compoundsinvolved. All detectors function to sense andmeasure the quantity of each sample componentas it comes off the colvm,.. Thc detectorsignals a recorder system which registersa response.2-4 A

As with other instrumental methods, standardswith known concentrations of the substance ofinterest are measured on the instrument. Acalibration (standard) turve.can be developedand the concentration in a sample can bedetermined from this graph.

Gas-liquid chromatography methods are verysensitive (nonogram. picograrn quantities) soonly small amounts of samplesare required.On the other hand, this extreme sensitivity .often necessitates extensive clean-up ofsamples prior to GLC analysis..VIII AUTOMATED METHODS -

. The increasing number of samples andmeasurements to be made in water qualitylaboratories has stimulated efforts to automatethese analyses. Using smaller amounts ofsample (semi-micro techniques). combiningreagents for fewer measurements per analysis,and using automatic dispensers are all meansof saving analytical time. r

However, the term "automated laboratoryprOcedures" usually means automatic intro-

: duction of the sample into the instrument,automatic treatment of the sample to test lota component of interest, automatic recordingof data.-and, increasingly, automatic calculatingand print-out of data. ,Maximum automationsystems involve continuous sampling directfrdm the source (e.g. an in-place probe) with

'telemetering of results to a centraltcompther,Automated methods, espycially those based oncolorimetric methodology, are recognized forseveral water quality parameters includingalkalinity, ammonia, nitrate. nitrite, phosphorus,and hardness.

IX SOURCES OF PROCEDURES

Details Of the procedure for an individualmWasurement can be found in reference ho,,Ics:There are thret particularly-recognized booksof procedures for water quality measugements.A Standard Mei%orls(1)

The American Public Health Association,the American Water Works Associationand the Water Pcllution Control Federationprepare and publ.sh "Standard Methods forthe Examination of Wat.. and Wastewater."As indicated by the list of publishers, thisbook co ntains methods developed for use bythose interested in water or wastewatertreatment.

B iViTM Standards(2)

The American Society for Testing andMaterials publishes an "Annual Book ofASTIVY Standards" containing specificationsand methods for testing 'materials. The"book" currently of 47 parts.

14

Methodology for Chemical Analysis of Water and Wastewater

.5

The part applicable to water was formerlyPart 21. It is now part 31, Water.

The methods are choseriby appxo(oal of themembership oLASTM and are intended toaid industry, go:ernment armies and thegeneral public. Methods are applicable toindustrial waste waters as well as to othertypes of water samples.

C EPA Methods Manual131

The United States Environmental protectionAgency publishes a manual of "Methods forChemical Analysis of Water and Wastes."

EPA developed this manual to providemethodology for monitoring the quality ofour Nation's waters and to determine theimpact of waste discharges, The test pro-5edures were carefully selected to meetthese needs, using Standard Methods andASTM as basic:references. In many cases.the EPA manual contafns.completelydescribed procedures because they modifiedmethods from the basic references. 0,ther-wise, the manual cites page numbers inthe two references where the analyticalprocedures can be found.

X ACCURACY AND PRECISION

A Of the,alethod

One of the criteria for choosing methodsto he used for (eater quality analysis is thatthe method should measure the desiredproperty or constituent 'with precision.accuracy. and specificity sufficient to meetdata needs. Standard references, then,include astatetnent of the piecision andaccuracy for the method which i btainedwhen (usually) several analysts _ :ifferentlaboratories used the particular method.

B Of tbe Analyst

Each analyst ahouldcheck his own precisionand accuracy as a test of his skill in per-forming a test. According to the U. S. EPAHandbook for Analytfeal Quality Control(4),he can do this in the following manner.

To check precision, the analyst shouldanalyze samples with four differentconcentrations of the constituent of interest.seven times each. The study should coverat least two hours of normal laboratoryoperations toallow changes in conditionsto affectjhe results. Then he shouldcalculate the stancrard-deviation of each ofthe sets of seven results and compare l_tisvalues for the lowest and highest concen----Mations tested with the standard deviation

'value published for that method in the.referenctbook. At 'individual Should have better valuesthan thbse averaged. from 'the work of severalanalysts.

To check accuracy, he canuse two of thesamples used to check precision by addinga known amount (spike) of the particularconstituent in quantities to double the lowestconce.itration used; and tobririg ata inter-mediate concentration to approximately 75%of the upper limit of application of themethod. He then analyzes each of the spiked

average of ea set of seven results. ;To'samples sev rVitnes. then calculates the

calculate accuracy in terms of % recovery,he-will also need to calculate the average ofthe results he it when he analyzed theunspilied sampi:s. Thett

Avg..of Spiked% Recovery = I Avg. of + Amt. of X 100

Unspiked Spike

Again, the individual's % recovery 'should bebetter than the published figure derived fromthe results of several analysts,.

C Of Daily Performance

Even after ant analyst has demonstrated hispersonal etill in performing the analysis,a daily check on 13;ecision and accuracyshould be done. About one in every tensamples should be a duplicate to checkprecision and about one in every ten samplesshould be Spiked to check accuracy.

It is also beneficial to partica.patein inter-laboratory.quality control programs. TheU.S. EPA proVides reference samples atno charge to laboratories. These samples

t.

Methodology for (ibex/nes; Analysis of Water and Wastewater

serve as independent checks on reagents.instruments or techniques; for traininganalysts or for comparative analyses withinthe laboratory. There is no certificationor other formal evaluative function resultingfrom their use.

XI SELECTION OF ANALYTIC 1LPROCEDURES

Standard scurcestl 2.3) will, for mostparameters. contain more than one analyticalprocedure. Selection of the procedure to beused in a specific instance involves consider-ation of the use to be made ofthe data. Insome cases, one must use specified procedures.in others, one may be able to choose amongseveral methods. '

,6

A NPDES Permits and State Certifications

A specified analytical procedure must beused when a waste constituent is' measured:

For an application for a National PollutantDischarge Elimination System (NPDES)permit under Section 402 of the FederalWater Pollution Control Act (FWPCA).as amended.

2 For reports required to be submitted bydischargers under NPDES.

3 For certifications issued by Statespursuant to Section 401 of MI FWPCA.as amended.

Analytical procedures to be'used in thesesituations must conform to those specifiedin Title 40. Chapter 1, Part 136, of theCode of Federal Regulations (CFR). Thelistings in the CFR usually cite two differentprocedures for a particular measurement.

The CFR also provides a system ofapplying to EPA for permission touse methods not cited in the CFR.Approval of alternative methods fornationwide use will be published inthe Federal Register.

2-6

#

B Ambient Water QuaL.y Monitoring

For Ambient.Water Quality Monitoring,analytical procedures have not is -enspecified by regulations. How. r, theselection of procedu:en to be used shouldreceive attention. Use of those listed inthe CFR is strongly recommended, Ifany of the data obtained is going to be usedin connection with NPDES permits, or maybe used as evidence in a legal proeieang.use of procedures listed in the CFR isagain strongly recommended.

C Drinking Water Monitoring

In December, 1975. National InterimPrimary Drinking Water Regulations-) be effective June 24, 1977 werepublished the Federal Register inTitle 40, Chapter I, Subchapter D.Part 141. The publication includesspecification of analytical proceduresto' be used determining compliancewith the r,...1.it.turn contaminant levelsof requireri ,:.rameters.

Because of the low concentrations in-volved in the regulations, there is oftenjust one (analytical method cited foreach parameter.

Individuals or organizations may applyto EPA for permission to use methodsnot cited in the above. Approval ofalternative methods for nationwide usewill be published in the Federal Register.

XII FIELD KITS

Field kits have been devised to performanalyses outside of the laboratory. The kitmay Contain equipment and reagents for only.one test or for a variety of measurements.It may be purchased or put together by anagency to serve its particular needs.

Since such kits are devised for performingtests-with minimum time and maximumsimplicity, the types of labware and reagentsemployed usually differ significantly from theequipment and supplies used' to perform,thesame measurement in a laboratory.

Methodology for Chemical Analysis of Water and WaStewater

A Shortcomings

Field conditions do not accommodate theequipment and servicer, required for pre-treatments like distillation ancdigestiOn.for is'it practical to carry and use calibrated

glt ware Ake burets and volumetric pipets.Other problems are preparation. transportand storage of high quality reagents. ofextra supplies required to test for and removesample interferences before theMeasurement. and of instruments whichare very sensitive In detecting particularconstituents. One just cannot carry and.set up laboratory facilities in the field whichare equivalent to stationary analyticalfacilities.

B Uses

Even though the results of field tests areusually not as accurate and precise as those

. performed in the laboratory, such teats dohave a place in water quality programs.

In situations where only an estivate o/ theconcentrations of Various constituents isrequired, field tests serve well. They areinvaluable sources of inforMation forplanning a tyli-scaltaampling/testingprogram wnn deeisiOns must be maderegarding locatiOhof sampling often.schedule of sample collection. dilution ofsamples required for analysis. and treat-ment of samples required to remove inter-

.ferences to analyses.

C NPDES Permits and State Certification

Kit methods are not approved for obtainingdata required for NPDES permits o, Stateconstruction certifications. If one judgesthat such a method is justifiable for thesepurposes. he must apply to EPA for per-mission to use it.

Drinking Water Monitoring

The DPD test kit for residual chlorine isapproved in the December. 1975 FederalRegister for monitoring drinking water.

REFERENCES

1 Standard Methods for the Examination ofWater and Wastewater. 14th Edition.1978, APHA-AWWA-WPCF, 1015 18th Street.N.W., Washington. D.C. 20038

2 1975 Annual Book of ASTM Standards.Part 31. Water. ASTM. 1918 Race StreetPhiladelphia, PA 19103.

3 Methods for Chemical Analysis of Waterand Wastes. 1974. U. S., EPA, EMSL,Cincinnati. OH 45288.

4 Analytical Civallty Control in Water andWastewater Laboratories. 1972. U, S.EPA, EMSL. Cincinnati. Ono 45288.

This outline was prepared by A, D. Kroner.Chemist, National Training and OperationalTechnology Center. MOTD.SWIP0, USEPA.Cincinnat. Ohio 45288.

Descriptors: Analysis. Chemical Ana lykis,Methodology. Waetewaler, Water Analysis

2-7

STATISTICS FOR CHEMISTS4

1. INTRODUCTION

A Statistics may be defined, for our purpose,as a collection of methoas which have been

. developed for handling numerical datapertaining to samples or portions of entirepopulationil.

B The statistical methods with which we will"concern ourselves deal with the presentationand analysis of numerical data from samples.

FREIZLIENCY

A Definitions

1 Frequency - indicates how many timesa particular score occurs in a -collectionof data

ST. 25b. 11.77

,2 Frequency table - a tabular arrange:ment of data, ranked in ascending ordescending order of magnitude,together with the correspondingfrequencies

3 Frequency histogram - a set ofrectangles having bases on a horizontal

.axis with centers at the given scoresand heights equal to the correspondingfrequencies (See Figure'l)

4 Frequency selygan - a-line .graph offrequencies plotted against scores(can be obtained by connecting mid-points of tops of rectangles in thefrequency histogram) (See Figure 1)

Figure 1

Frequency HTetogram & Frequency Poli,gion

98 99 100 101

Chloride pg/1

13

102

.-3- :

Statistics For Chemists

B Application

Consider the application of :he abover. definitions to the following set of data,.

obtained from twelve determinations forchloride in' aster.

Results (gel)100 101 99

101 100. 100

99 '102. 100

98 101 102

,Table 1Frequency Table

Chloride (y4/1) Frequency

98 1

az

100

lot102

2

4

3

2

III MEASURES OF CENTRAL TENDENCY

A Definitions

1 Central tendency - the Pendency ofvalues to cluster About a particular,.7aluo.in the distrAotion

2 Mode - that valuPwhl",occurs mostfrequently,

3 Median.- midpoint of an filar , ofscore*. If there is an odd aber ofobservations, n, theiedia

xn +1 where 11. +.1 represents2 9 2

the ". 1 value in the frequency

distribution. If there is an even

3-12

number of observations the median isX ice X n

+ 12

2, the average of the#'

.middle two scores. ,

4 Mean - arithMetic average of all thevalues in the sample distribution, de-noted by Tc: The formula for calcula-ting the sample mean is

4-X2 X

E Xi

n

a EX.i where there are n numbern of values.

B Aids in calculation of the mean

Application of the following two statementscan reduce errors and amount of timespent in calculating the mean of adistribution.

1 Adding or, subtracting a constant to orfrom each.score in distribution is.equivalent to adding or subtracting thesame constant to or from the mean ofthe distribution. Thus the followingformula:

lc g ± C where theXi's are thevalues in the distribution with mean L.and the Xi t C's are the values in thedistribution with Mean Xc.

2 Multiplying or dividing each score inadistrihution by a constant is equitialentto multiplying or dividing the mean ofthe distribution by the same constant.

. Thus the following forinulas;

(I) In CR

or

(2) Rc Tti where the Xi's are thevalues in the distribution with mean R,

19

and the CXi's Or the C ts4re thevaluea in the distribution with mean

,

C Application

Consider the application of the abovedefinitions to the previously, mentionedset of data,. obtained froM twelve deter-minations for chloride in water, Shown,in Table 1.

1 Mode .100

,

2 Median

x.n + xn

2

100 + 100100

2

'2(6 +2 X1

3 Mean .98 + 2 (99) + 4 (100) + 3 (101412 (102)

12

100.25

4 Aid in Caliulation

Consulting Table 1 and observing thatthe values are In the neighborhood of

'100 we mighfirebtract 100 from eachscore and Oitaig the following distribution:

Table 2

Frequency Table

Chloride (4g/1) Frequency2 1

-1 2

0 4

3

2

Statistics for Chemists

Denote the mean of ttukdistribution inTable 1 byX If we add 100 to each

, scoe'in the distribution in Table 2,' weobtain the scores in the lstribution inTable 1; likewise if we add 100 to themean, X, of the distribution in Table 2,we obtain the mein, , of the distri-bution in Table 1. c

, Thus.; ic;+ 100

EXX + 100r.) c n

1(-2) + 2(-1)+ 4(0) + 3(1) + 2(2) +.10012

Xc .25 + 100, 100.25

'IV MEASURES OF.DISPERSION

A Definitions

'Dispersi6n - spread or variability of. observations in a distribution

2 Range - the difference between thehighest value and th, lowest value

Ft nfax'- min

3 Average deviition - the sum of thedeviations of the val.4es from theirmean, without regard to sign, dividedby the total number of data values (n)

The formula for calculating the averagedeviation is:

Elxa

203 -I.


4 Average deviation of the mean (3) -the average deviation of individual,data items from the mean (d) dividedby the square root of the number ofdata items (n)

The definition of the average deviationof the mea can be expressed by theformula:

D

5 Variance - the sum of the squares ofthe deviati-ms of the values fiorn theirmean divided by the total number of .

data values (n) minus 1

The definition of the variance can beexpressed by the following formula:

E(Xi - X)2n - 1

6 Standard deviation - the square rootof the variance

The definition of the standard devititioncan be expressed by the followingformula:

- 5-02

B n - 1

we

However, the formula commonly usedbecause of its adaptability to the' handcalculator is the following:

EX2 (EX02i n

" n -1 whn n mber of values.

there are

'7 Standard of the mean (S) - the .

standard deviati n of individual data,items (s) divided by the square root ofthnu-nber of data items (n)

3-4

The definition of the standarddeviation of the mean can beexpressed.by the formula:

3-47,

8 Relative standard deviation - thestandard deviation (s) expressed asa fraction of the mean, s

The relative standard deviation isoften expressed as a percent,, It is'then referred to as,thc coefficient .

of variation (V):

V t X 100 .

The relative standard deviation isparticularly helpful when comparingthe precision of a number of deter-minations on a given substance atdifferent levels of concentration.

B Aids in Calculation

Application of the following statementscan reduce errors and amount of timespent in calculating the variance orstandard deviation of a distribution.

1 Adding or subtracting a constant to or'

from each score in a distributiondoesn't affect the variance or standarddeviation of the distribution.

Thus the following formulas:

2 82

(2) sc

s

where the Xi's are the values 'the distribution with variance aand standard deviation s, and theXi C's are the values in thpdistribution with variance sc`and standard deviation sc.

21.

Statistics or Chemists

2 Multipixhrg or dividing each score ina distri.,arion by a constant is equivalentto Inuit/plying or dividing the varianceof that distribution by the square of thesame constant.

Thus :the following formulas:

(l) '. 662 C2s2

(2)111(c2 13-2:Cz6

v

- where ihe Xi's are the values inthe distributiori with variance s 2,and the.00i's or the Xi 's are ,the values in the distribution withvariance ec2'.

3- Multiplying or dividing each score in adistribution by a constant is equivalentto multiplying or dividing the standard

'deviation of that disgiibution by thesame constant.

Thus the following formulae:

(1) s Csor(2) sc

where the Xi's are the values inthe dist ibution with standarddeviation nd the (Mee or tne

Xi 's are the values in the

distribution with standarddeviation sd.

C Application

Consider the application of tha abovedefinitions to the previously mentionedset of data, obtained from twelvedeterminations for chloride in water,sliown in II B, Table 1.

1 Range 102 -98 4

2 .Average

n

deviation - d

Xi IXi- RJ nIX

LIXI F°n -, NI

RI

1 98 2. 25 2. 25

2 99 1.25 2.504 100 .. 25 1.00

3 101 .75 2. 25

2 102 1.75 3.50,Tc 100. 25 11.50

RI 11,50 .96.£)X-n 12

3 Average deviation of the mean:d_

Using calculations from number 2,

D d "67 °96 0.284-rff- 3.46

4 Variance - £(X {- 562s2n- 1

n Xi Xi -X (xi- )7)2 n(xi- ic)21 88 -2.25 5. 06 5.062 99 -1.25 1.56 3. 124 Igo - 1. 25 .06 . 24

3 101 4 +Q75 .56 1.682 102 +:.75 3.06 6.12

16.22.2 Z(Xi- To2 16.22 1.47n- 1 11

3-5

lo


5

n

1

2

4

3

2

Standard deviation

311 n2Si_

98 98'

99 198

100 400

101 ,303

102 204

1203

s

3Li2

9604

.9801

10000

10201

10404

.2

s

7

(217 12 16.25 1.48

1.22

I

(zxL)2EXi 11

Tr-

..

- 1

.,...,,2.i9804

19602

40000

30603

20808

EX 2 - (EX )2.i i jr.-irn - 1 . -

Standard 'deviation of the mean -

S' s-120617 ,

20817 - 12032

. 11/120617 - /20801

11

.11

El TT 1:21/a

2

6 Aid in calculation

Recalling that adding or subtracting aconstant to each score in the distri-bution doesn't affect the variance orthe standard deviatiod of the distribu-tion we can simplify the computationsby first.subtractins.E10 from eachscore in the distrMtion. thus obtain-ing the frequency distribution shownin Tau le 2.

a .

n .Xi-C noti-C) 04-C/2 nOiiiC)2

1 4 4

2 -1 -2 1 2

4 ; 0 0 0 0

3- 1 3 1 3

2 2 4 4

3

2 (EXi)2

E X -

17,

.2 i nn - 1

Using calculations from number 8.

Se 1.22 1.22

rr2 3.46

8 Relative standar deviation eicpressedas a yercent ( efficient of variation)

v a x

Using calculations from number 6 for's 1.22 and from number 2 for.X r 100.25.

22 x 100 1.21%X 100,2

)figure 2Normal Distribution Curve

g.

Quantity Meastired

3-6 23

I.

Statistics for Chemists.

V INTRODUCTION TO NORMALDISTRIBUTION CURVE

A Statistics deals with theoretical curveswhich are smoother than frequencypolygons, obtained from experiments inreal We. However, frequency distribu-tions or frequency polygons of ex,,erinkentaldata often approilmate a mathernatipalfunction called the ''normal" distributioncurve. (See Figure 2)

As shown in Figure 3, the frequency polygonfor the 12 determinations for chloride inwater isa fairly good approximation of thenormal curve. If, however, in the chloridedeterminations we had.obtained 103 insteadof 98 and 104 Instead of 99 this distribution .

would not have been a good approximation ofthe normal curve, as is shown in Figure 4.

Figure 3

Comp., on-of Normal Curve and Frequen ;y Polygon

,197 . 98

5-99 100 101

Chloride II gil

'102

Figure 4

Comparison of Normal Curve andFrequency Polygon

99 100 101 102 p- 103

Chloride II gil

.14

104

3 -7

. .Statistics for Chemists

B If a frequency distribution'is a good Figure 5 shows the normal distributionapproximation of the normal curve, we in teams of the population mean g, andcan use some facts about the normal the standard deviation of the populationcurve to give, us information about the a, and gives the percent of area underfrequency distribution, the curve between certain p,pinte,

3-8

Figure 5

Normal Distribution Curve

4

3

2

1

Figure

Frequency Distribution

0'

6

Polygont

5%

1I

,e t00%

1 tIs +ZsBB IS 100 101 102

Chloride pg/1


We may check the distribution of sampledata to see if it is a ''normal" distributionin the following manner. Substitute thevalue of the sample mean (X) for the valueof the midline and substitute the value ofthe sample standard deviation (s) for thelimits of the value spans where we mightexpect certain percentages of the dataitems to occur. Then we can check thenumber of data items which actually dooccur within these value spans.

Figure 6 demonstrates this applicationusing the chloride data values from Table 1.The data values are markexi on the hori-zontal line and the frequency-ofoccurrence of each value is marWd on thevertical. The midline of the distributionis marked at the value of the sample mean(3C 100, See III C 3). The value of thesample standard deviation is 1.21, SeeIV C 5) is used to mark value areas underthe curve where different percentages ofdata values will probably occur. Thus,for the area X 1- ls, X - le 98.79 andX + 1 s 101.21. Therefore, accordingto the normal distribution curve shown inFigure 5, we might expect about 68% of 1h9data items to have values between 99 and101. (The values are rounded to wholenumbers since the data values are thusrecorded).

Consulting Table 1, we find that 75% qrof the 12 data items have values in thisrange. This percentage is shown inFigure 6 by the frequency polygon for thedata shown earlier in Figure 3.

'Likewise assuming a normal distribution,we would expect 9570 of the observatiOneto lie within +20 'a from the populationmean. In fact, 100% of the observationswere within 2 s's frcmthe sample mean.

In both cases the obsers*d percentages are...reasonably close to the expected percentages."Other tests exist for determining whether

or not a frequency distribution mightreasonably be assumed to approximatethe normal distribution.

ft would be good to become as familiar aspossible with the normal distribution sincean underlying normal distribution isassumed for many statistical tea's ofhypothesis.

REFERENCES

1 Bennett, C. A. and Franklin, N. L.Statillticol Analysis in Chemistry andthe Chemical Industry. John Wiley& Sons, Inc., New York. 1954.

2 Crow, E. L., Davis, F. A. , and Maxfield,M. W. Statistics Manual. DoverPublications, Inc., New York. 1960.

3 Dixon, W.J. and Massey, F:J.Introduction to Statistical Analysis.McGraw ,Hill Book Co.. Inc., NewYork. 1957.

4 Ostle, Statistics in Research, The- Iowa State University Press, Iowa,

1963..

5 Youdon, W.J.Chemiats,New York.

Statistical Methods- forJohn Wiley & Sons, Inc.,1951.

This outline was prepared by L. A. Lederer,Statistician, formerly with AnalyticlilReference Service, Training Program,NCTJM, SEC. Revised by Audrey D.Kroner. Chemist, National Training andOperational TechnOogy Center, MOTD, OWPOUSEP4, Cincinnati, Ohio 45268,

Descriptors: Graphic Methods, Quality Control,'Statistical Methods, Statistics

3-9

ACCURACY-PRECISION-ERROR

ti

I INTRODUCTION

An analytical method is subject to errors.These errors may affect the accuracy of themethod because they infroduce bias into theresults. There are other types of errorswhich affect the precision of the methodbecause they produce random fluctuations inthe.data. The most desirable situation forthe analyst is shown in the diagram inFigure 1 where the results are both preciseand accurate.

ti

IMPRECISE AND INACCURATE

PRECISE BUT INACCURATE

if-'ACCURATE BUT IMPRECISE

PRECISE AND ACCURATE

Figure 1. PRECISION AND ACCURACY

CH. MET. con. Id.11. 77

A Accurady

For results to be accurate, the analysisused must give values close to the truevalue.(See Figure 1)

B Precision

Precision is the'degree of agreementamong results obtained by repeatedmeasurements on a single sample undera given set of conditions. It is a measureof the degree to which results "check."(See Figure 1)

C Note .'

Itds possible to have precision withoutaccuracy. (See Figure 1)

II DETERMINATE ERROR AND ACCURACY

A C.,..terminate error is one which con-h tributes a constant error or bias to reitults,

causing them to be inaccurate. Thisconstant error makes it possible for resultsto agree with each other (be precise) andstill be inaccurate.( See Figure 1) .

Determinate errors have "assignable"causes Which can usually bedentified andeither eliMinated or controlled. (The terms"determinate" error, "assignable" error,and "systematic" error are synonymous).

27

Sources of Determinate Error

1 Method error

Method errors are those that areinherent in the,procedure. These arevery serious and the hardest to detectand correct. The most commonmethod error is the presence of inter-ferences in the sample. Otherexamples would be precipitation ofsubbtances other than the desired.material, partial solubility of pre-cipitates, and entrainment as in asolvent extraction procedure.

4-1

A ccuracy-P recision-Error

2 Personal errors

Personal errors are attributable toindividual mistakes which are con-sistently made by an analyst. Theseerrors are the result of consistentcarelessness, lack of knowledge orpersonal bias. Examples are errorsincalculatimus, use of contaminatedr ea :As, non- representative sampling,or poor calibration of standards andinstruments.

3 Instrumental errors

Instrumental errors are those whichare caused by an analytical instrumentor by the effects of the environment \ -

acting on the instrument: Moisture in aG. C. column, improper wavelengUf

on a spectrophotometer orincorrect scoring on a buret would beexamples. I

B Effects of Determinate Er ;or

, 1 A dditive

An additive determinate error.is onewhich has a constant value regardless'ofthe amount of analytically sought con-stituent present in the sample.(See Figure 2)

2- Proportional.

A proportional determinate errorchanges value according to the amountof analytically sought constituent in thesample. .(See Figure 3)

III DETECTION OF DETERMINATE ERROR

A Spliced Samples

1 Samples which can be determined beforeand after the addition of a known con-stituent ( in the concentration range ofinterest) provide a way to detectdeterminate errors. Spliced samplesshould be representative and resemble

'actual conditions as closely as possible.The quantitation of bias can then beobtained with the following measures.

4-2

a Mean error - the difference betweenthe mean of the data and the trueresult.

b Relative error - the mean error ofa set of data expressed as a per-centage of the true result.

EXAMPLE: An analyst determinesthe nitrate content of the effluentfrom his sewage treatment plant to be0.50 mg/I. He then adds 1 mg/1 ofstandard nitrate solution to thesample. Table 1 shows the replicateresults obtained 'oi the spikedsample, and calciation of bothmean and relative errors.

Table 1

Sample: 'EffluentDetermination: Nitrate (Modified Brucine)

Xi

1.351.47

1.491.55

1.561.59

1.60

1 Calculation of mean error10761

A 1.51 mg/1

Mean Error s' 1.51 -1.50+0.01 mg/ I

2 Calculation of relative error.1- 0.01 X 1001. Relative Error. 1.50 +0. 7

2 'Control charts

Tress's and shifts on control chartsmay also indicate determinant error.Using spliced samples, the standarddeviation is calculated and controllimits (usually + 3 standard deviations)for the analysis are set (see Figure 4,For further discussion of control limits,see reference 3, p. 62.

23ti

Accuracy-Precision-Error

j1 2 3 4 3 4,

THEORETICAL VALUE THEORETICAL VALUEFigure 2. ADDITIVE ERROR Figure 3. PROPORTIONAL ERROR

100

150

700

130

DPP I CONTROL LIMIT...

LOWER..I

CONTROL LIMIT

0 OUT TrOL

2 3 4 3 6

DAY NUMBER

Figure 4. CONTROL CHART

9

35

-35

10


3 In some cases, it is impossible tospike a sample sathat it resemblesactual conditions (e. g. , BOG andpesticide samples). Youden (11)provides excellent techniques fordetecting bias in this situation.

B Unknown Samples

1 Independent method

Analysis of a sample for a desiredconstituent by two or more methodsthat are eidirely different in principle(gravimetric and volumetric) may aidin the estimation of determinate error.However, another reliable method maynot be available or may be laborious toperform.

2 Control charts

It is possible to plot a control chart(Figure 4) even when it is not possibleto spike a sample. One can use as areference value an average of a seriesof replicate determinations performedon a composite check sample. Stich asample must be preserved or stabilizedin such a way that the concentrationof the constituent being measured willnot change from day to day (seerefer ence 1).

3 Aliquoting

U the determinate error is additive,the magnitude may be estimated byplotting the measured quantity versusa range of sample volumes or sampleweights. U the error has a constantvalue regardless of the amount ofaruilytically sought constituent, thena straight line fitted to the points willnot go through the origin. (See Figure 5)

C Youden's Graphical Technique (10,11,12)'

Dr. W. J. Youden has devised anapproach to test for determinant errorswith a minimum of effort on the partof the analyst and his laboratory.Samples used may be of known (spiked)or unknown composition.

4-4

1 Technique

Two c..fferent test samples (X and Y)are prepared and distributed foranalysis to as many individuals orlaboratories as possible. Eachparticipant is asked to performonly one determination on eachsample (NOTE: It is importantthat the samples be relativelysimilar in concentration of theconstituent being measured).Table 2 shows the results on two-such samples analyzed for percentpotassium by 14 different laboratories.The mean for each sample has beencalculated.

2 Interpretation Figure 6

The vertical line drawn on thegraph represents the mean (X)of all the results obtained onSample X; the horizontal line wasdrawn through the mean (Y) of allthe results obtained on sample Y.Each pair of laboratory resultscan then be plotted as a point onthe graph (marked X'. 1 etc.)

If the ratio of the bias (error) tostandard deviation is .close to zerofor the determinations submittedby the participants, then one wouldexpect the distribution of the pairedvalues (or point's) to be close toequal among the four quadrants.The fact that the majority of thepoints fall in the (+, +) and (-, -).quadrants indicates that the resultshave been influenced by soma sourceof bias or determinate error.

Furthermore, one can even letirnsomething about a participant's;precision from the graph. If allparticipants had perfect iirecision(no' indeterminate error), then all

.

the.paired points would fall on a450 line passing through the origin.Consequently the distance from sucha 450 line of each participant'spoint provides an indication pf thatparticipant's precision.

Accuracy:Precision-Error

3. Examples of Youden two-samplecharts are in the Appendix (p4-13).

4. A quantitative treatment of this .subject can be found in references11 and 12.

a.

6

.02N 2

01 2 3

TS AMPLE VOLUME lin0

Figure 5

4

Table 2

Laboratory St ample X Sample Y

1

2

3

4

9.74%9.929.989.99

8.50%8.288.848.24

5 ' 10.00 e 8.736 1041 8.547 10,12 8.648 .10.14 8.82

,.9 10.19 9.04

10 10.23 8.9311 10.25 8.9712 10.29 8.8013 10.55 9.2114 , 10.62 8.95

3C- v 10.15 8.75

9.20

9.00

LSO

11.60

4.40

5.20

son

0. .

.. .

X II

X13

;p I' x

X

9Xx

10, X

4

goz

11

x'12

,____X.

/ 1

rx6

X2 X

SAMPLE X IVO

'

9.00 9.20 9.40 9.60. 9.114 10.00 10.2.p io 40 10 60

Figure O. YOUDEN'SGRJOPHICAL TECHNIQUE

31

10 SO 11,00.

4-5

IV ELIMINATION OF DETERMINATEERROR

Various approaches can be'used to eliminatethe source of determinate error. Theapproach used depends upon whether thesource is personal, method, or instrumental.

A Personal

Great care must be used to avoid producingan unconfident attitude in a technician. Itis undesirable for the analyst to feel he isbeing "policed."

B Method and Instrum.ental

1 Blanks

Blanks can be used to correct forinterferences from reagents, samplecolor, etc.

2 Correction factors

Examples of cormction,factors usedin environmental analyses to eliminatedeterminate errors are the following:

a Recover:. factors in organicextractions

b Chemical yield values in gravimetricanalyse*

c Counting efficiencies for radiationcounters .

3 Standard addition

Sample interferences producing deter-minate errors can be overcome byadding equal amounts of unknownsample to a series of standards. The .

concentration of the unknown can thenbe determined graphically from a plotof the measured quantity (absorption,emission, etc.) versus the standardconcentration. (See Figure 7)-

4-6

Figure 7. .t :THUD OF STAND., RDADDITION GRAPHICAL NIKTIKHCOMPUTING Sr C(1XCENTRATIL

r: 90z4.7s

70

o 504.7s

191111111MIIIMIIIIX

"19

40 4 4Srf*CONC (00/1)

0

NOTE. The X value appearing along the, abscissa 20. X 40. etc.) re-

fers to the unknown added to the strontiumstandard

4 Standird compensation

Another appro-ach is to prepare thestandtard so that its izompositionresethbles that of the sample asclosely as, possible. The objectiveOf the approach is exactly the sameas that of standard addition - tocompensate for'the presence ofinterfering substances in the unknown.

V INDETERMINATE ERROR ANDPRECISION

Even when all determinate errors areeliminated, every replicate analysis willnot give the same value. Such variationin results is due to indeterminate error,also known as random, chance oruncontrollable error. Indeterminateerror affects the,precision or agreementamong, results;

32.

Accuracy - Precision -Error

A Sources of Indeterminate Error

Indeterminate errors are due tounassignable or "chance causes."Examples are inadvertent contaminationof sample or glassware, variation inreagent additions, or variations ininstrument response (see Figure 8).

13 Effects of Indeterminate Error

Since thr causes of these errors arerandom, the effects are also random.Fortunately,.these random variationsconform to the "Laws of Chance" so*statistical measures of precision can beused to quantitate indeterminate errors.

VI DETECTION OF INDETERMINATEERROR .

A measure of the degree of agreement amongresults can beobtained by analyzing a singlesample repeatedly under a given set ofconditions.

A Range

The range of the replicate results(difference. between the lowest and thehighest value) provides a measure ofIndeterminate variations.

B Standard Deviation

An estimation of indeterminate error canbe obtained through a calculation of thestandard deviation. The following formulasshould be applied to random data whichfollows a normal distribution. Normalitycan be checked by ranking and plotting thedata on normal probability paper; it shouldfall on a straight line (see Figure 9). Anyvalues which do not fall close to the straight

line (tise values encircled) should bereject In the calculation of standarddeviation. Other-statistical tests (8)can be used to objectively evaluate therejection of outliers. The value obtainedfor standard deviation for a particularmethod may vary with the analyst, theconcentration range of tile constituent,and the composition of the sampleanalyzed. The confidence of theestimate is increased as the number ofresulta (n) used to compute the standarddeviation is increased.

1 Replicate results on the same sample:

/roc - TO2

8 n11 (1)

Xi = value of single result

X .., average (mean) of results onsame sample

n = number of results

Example: Table 3 contains a set of 5-dayBOD results obtained on a syntheticsample containing 150 mg/1 of glucoseand 150 mg/1 glutamic acid. (Note: A 1%dilution was used in the actual test). Theresults are those submitted by laboratoriesparticipating In a colaborative study.Calculate the standard deviation of theseresult's.

171 = 192 mg /1

n 36.0

Yi)2 = 58, 200

spuor35

41 mg/1

4

4-7


7t BECKMAN B (650 .4METHYLENE BLUE SOI1UTIONIra CELL'6 25 REPLICATE READIN

5

5-LP 4z

e 3cc.1.

S

a

2 X,-

X X

,x

X X

X

X ,x

I I I I I I I I I j.528 .530 .532.. .534 .536

ABSORBANCE..

Figure 8. VARIATIONS IN SPECTROPHOTOMETER READINGS

F GURE9 NORMAL PROBABILITY CURVE

40

I50_400

ISO

580

140

520

100

LIO

280

240

MO 140 all no 10 a 0 is 0 0 0 10 0 1

f

2 1 0$

I

OS 01 GO 00

. - 4240 SLID

,

.

,.

I 141 ....

.....4:

220UM

.,...''.*....

.

i II0

, -

...

°ACM imam a. 0 1 2 1 0 00 0 10 1111 10 0 1110 OS 0114458149 Won* I 2a. 2081

I 34

'9

Accuracy - Precision -Error

Table 3SAMPLE: 150 mg/I glucose 150 mg /1 glittamtc arid (1% dilution/DETERMINATION: 5-day Biochemical Orygen Demand

a.

Xa Xi - - 302 xi xi Oc; - ro2

100 mg/1117125

-92 mg/1-75-67

8464 Dag/0256254469

198 mg/1199200

6 mg/17

8

36 (mg/11249

. 64

132 -60 3600 200 8 64142 -50 2500 204 12 144147 -45 2025 210 18 326

153 -33 1521 211 19 361

10-32 1024 212 20 400

165 -27 729 215 23 529

165 -27 729' 213 '31 961167 -25 625 224 32 1024173 -19 361 227 35 1227

17a -14 . 196 229 37 1369187 - 3 9 38 .46 2116

'190 - 2 4 247 55 3025

.196 4 16 250 58 3744196 4 16 259 67 4489197 5 . 25 274, 82 6734

Data taken from Bitter. Oxygen Demand Report 1960). Analytical RefernceService. Training Program. R.A. Taft Sanitary Engtneenng Center. Cincinnati. 0100

Table 4 * CONCENTSAA1PLE: Aqueoua RANGE:DETERMLNAT1014, Phosphate (Lucerna, Cc 4e, and Prat Method)

30 -

Sample 519/1 P d , d2 Sample Mg/1 P d2

A 51 2 1. 54' 2 453 58

B' 39 0 0 3839

C 53 1 1 . :254 52

D 47 0 0 0 5847 58

E 50 1 P 5451 54

F 48 1 1 Q 5447 5450 0 0 K 4650 4847 0 2. 0 S 5247 51

1 42 0 0 5342 53

.1 50 .1 1 U 4651 47

K 59 1 V 4280 42

Data obtained from Frank Sohickner...gaitor and Gamble.CoMpany.

359

Accuracv-Precision-Error

2 Duplicate results on different samples

In a laboratory where duplicates areroutinely. run, it would be simpfe touse the following formula for eValuationof standard deviation.

E(d2) (See reference 5,2 k page 654) (2)

d difference between duplicates

k number of samples

Example: Table 4 contains a set ofphosphate results obtained on aqueoussam e range 100-200 mg/l.C ulate the s dard deviation ofr sults.

E(d2) = 16

k 22

44

.61 mg /1

3 Duplicate and triplicate results ondifferent samples

E(X. - R)2 (See reference 7,s t. - page 73) (3)-x riA,,rage of results on the

' same samplen = total number of resultsk number of different samples

Example:, Table 5 contains a set of %nitrogen reedits obtained on unknownorganic compounds..

Calculate the standard deviation.

E(Xi - 51)2 .2401

ein - k ,22

F457122

s .104%

4-10

4 Use of range to estimate standarddeviation

For a small number of replicates(n < 10). the range can be used toestimate the standard deviation (See'table 8 ).

ft

71-r-r

(4)

Example:. Table 7 contains a set ofreplicate nitrate results. Calculatethe standard deviation of these results.

a Use of formula (1)X 0.72 mg /1

n 5

E(Xi - X)2 .0134

4753714

s .058 mg/1

b Use of formula (4)

.14 mg/1

till 2.33

.14 mg/12.33

s .060 mg/1

C Coefficient of Variation

An estimation of indeterminate errorcan also be made by calculating theCoefficient of variation..

V 3- X 100

By comparing the standard deviation(dispersion) to the average or meanvalue (central tendency) in a set od dataand expressing this relative standarddeviation as a percentage, the analysthas a meaningful interpretation of thedegree of dispersion present. Indeter-

301


Table 5*SAMPLE: Lkiltrinn Organic Coco:144a 7 CONCENTRATIONDETLRAILVATION: Nitroge:, (E eldahl) RANGE, 107, - 20!.

aanole T.N. Xi - .2- R) Sample r,N 3c - g -To2A 16.98 16.97 .01 .0001 J 13.13 13.75 .18 .63:416..4; .01 .0091 13.56 lb .036116.90 16.50 0 0 K 10.34 10.27 .07 .004916.49 .01 . .0001 10. 19 .08 .006416.72 16.65 .07 .0049 17.16 17.15 .01 .000116.57. .08 .0064 17.13 .02 .0004,

13 17.52 17.38 .06 .0036 M 15.01 15.03 .92 .000417.60 . .02 .0004 15.05 -.02 .000417.63 .05 .002516.31 16.31 0 N 12.44 12.62 ,18 .034916;30 .0: .0901 12.70 .08 .0064

12.73 .11 .0121T 16.40 16.35 .05 .0025 O 14.37 14.37 0 016.21 :09 .0016 19.36 .0: .000116.35 0 0P 11.85 11.85 0 017.56 17:55 .01 .0001 11.85 0 017.54 .01 .0001 Q 14.76 19.73 .06 .003614.96 14.81 .15 .0225 14.70 .03 . :000914.66 .15 .0225 14.70 .03 .0009R 17. 19 17.:7 .C2 .00041 18.15 19.02 ,13 '.0169 17.14 .03 .000918.99 .13 .0168

Data obtained from 9 rack Schlckner, Proctor and Gamble Company.

Table P-2--FACTORS USED TO ESTIMATE THE STANDARD

DEVIATION FROM RANGE

Size <IN

of Sample In) a t4

2 1.13 .8873 1.69 .5914 2.06 .A615 2.33 .4306 2.53 .3957 2,70 .3706 2.65 .351

1.67 .13710 3,04 .325

Nat rella. 1:2494risaastal Statist12.) pp. 2-6..

Table 7

SAMPLE, Ohio River Water

DETERMINATION; Nitrate (Modified Bruclne)

0.55 mg/114 0.07 .00400.66' 0.04 .00160.70 0.02 .00040.76 0.04 .00160.79 60.07 .0040

a) I

Accuracy - precision -Error

urinate error would be 4he cause of unduedispersion.

Example: Table 3

41 tag/1

192 mg/1

41V = 192 X 100

V = 21%

D An indication of an individual's analyticalprecision can be obtained by his partic-ipation in an interlaboratory iitudy. Inthis case, the analyst performs onlyune determination od each of two samples.Using Youden's Graphical Technique asin indication Wan individual's precisionwas discussed previously in this outlinein III C. Also see the outline on "inter-

c.) 'laboratory Quality Control Studies."

REFERENCES

1 Accuracy in Clinical Chemistry. DadeReagents, Inc., Miami, Florida.

2 Allan, Douglas H. Statistical Quality'Control. Reinhold Publishing Corp.,. New York. 1959.

3 American Society for Testing MatetialsASTM Manual on Quality Control ofMaterials. Special TechnicalPublication 15-C. 1951.

4 Bauer, E. L. A Statistical Manual forChemists. Academic Press, New York.1960.

.5 Bennett, Carl A. and Franklin, Norman L.Statistical Anaysis in Chemistry andthe Chemical Industry. John Wiley &Sons, Inc., New York. 195't. ..

6 Chase and Rabinocvitz. Principles ofRadioisotope Methodology. MinneapolisBurgess Publishing Company. 1964.

4-12

7 Mickley, Harold S.,-Sherwood, Thomas K.and Reed,, Charles E. AppliedMathematics in Chemical Engineering.McGraw-Hill Book 1". -any, New York.1957.

8 Natrella, M.G. Experimental Statistics,National Br'-eau of Standards Handbook91. U.S. Dept. of Commerce. 19t

9 Schickner, Frank A. Personal Corn-muidcation. The Procter & GambleCompany, Miami Valley Laboratories,Research & Development Department,P.O. Box 39175, Cincinnati, OH 45239.

10 Youden, W. J. 'The Collaborative Test.JAOAC 46:55-62. January 1963.

11 Youden, W1-, J. The Sample, TheProcedure, and the Laboratory.Anal. Chem. 32:23-37A. Dec. 1960.

12 Youden, W.V. Statistical Techniquesfor Colhlkorative Tests. Associationof Official Analytical Chemists, Box 540,Benjamin Franklin Station, Washington,DC . 1967.

This outline was prepared by Betty A.Punghorst, former Chemist, NationalTraining Center; and revised by Audrey D.

.Kroner, Chemist. National Training andOperational Tec.violog-,y Center, MOTD,

. OTP0,USEPA, Cincinnati, Ohio 45268.

Descriptors: Accuracy, Data Colledtions,Data Procesidng, Error Analysis, Errors,Graphic Methocfr, Measurement, Monitoring,Preciaion, Quality Control

33

.56

.42

Accuracy- precision -Error

PPEND1IX

5 Flt NATI. SONS PIFROM: NE1101 STI111/

ANALYSES

4

CISION AM GINS ACCURACY.

I, MINERAL ASS PHYSICAL

7.1

6.1

5.0

4.0

3.8

2 02.0

lUE111J1 NITROGEN,81111 PRECISION. linoERROR. FROM: 10115NITWIT ANALYSES,

ME111115

Iat II/LUER.SYSTEIATIC.

STONY 2..NOM

It'

UJ

CUT

SAMPLE 11

3

LI SAMPLE 3.

2 3 .4 5

1.0

3.0 4.0 5.0 6.0 7.0

AMMONIA NITROGEN. mg N/UTER, UNITED *CURACYAS NEGATIVE 11AS. FROM: MEMO STOGY 2, NUTRIENT

ANALYSES. MANUAL MEMOS

.76

KIELIAIL NITROGEN. al 1/U1E1,11001 PRECISION.FINN: MEMO STIIIV.2, NUTRIENT ANALYSES.

YANK METHODS

:20

.

SAMPLE 1

21 .42-0 2

0.2

SAMPLE 5.

*04 .20 .52 .76

4-13

1.00

ELEMENTS OF A QUALITY ASSURANCE PROGRAM

1' WATER QUALITY DATA

A Importance

1 Criteria for decisions

a Planning

.13 Permit issuance

p Documentation System

1 Complete and permanent records mustbe kept by all field and laboratorypersonnel.

2 Any procedures undertaken as quality-checks should also be recorded, datedand signed.

c Compliance 3 The results of any quality checks shouldbe recorded, dated and signed.

d EnforcementAny checks by outside service personnel

e Evaluation of treatment processes should be recorded, dated, and signed.

f Research decisions E Quality Assurance Control Coordinator(2)

2 Effects of decisions 1 Overall responsibility for program:

a Social

b Legal

c Economic.

13 Requirements for Reliability

development. infplementation. administration.

2 Continuing assessment of level of operations'

3 Identification of training needs aid provi-.sion to accomplish

4 Coordinator for inter-laboratory qualitycontrol' programs

1 Specificity

. 2 Accuracy IT SAMPLE

3 Precision A Validity(3, 4. 5.6)

C Elements of Quality AsauranceW 1 Representative

1 Valid sample 2 Properly collected

2 Recognized methodology 3 Clean, appropriate containers

3 Control of services, Instruments, 4 Approved preservation measuresequipment and supplies

5 Analytical checks on containers and4 'Quality analytical performance preservatives5 Efficient data handling and reporting'

. CH. MET. con. 9.11. 77

6 Holding limed observed

4 5-1

Elements,of a Quality Assurance Program

B Integrity (2,7) . 3 Methods for Chemical Analysis of Watera and Wastes (8)

1 Written procedures for all aspects .

of sample handling 4 U.S. Geological Survey Techniques ofWater Resources Inventory(8)

2 Field labels. secords, seal

3 Appropriate transport to laboratory

in, system

5 App opriate storage conditions andholding time

6 System for distribution for analysis

7 Syetem for storage-or discard

8 System for chain-of-custody documen-tation

III` RECOGNIZED METHODCLOGY,

Need for Standardliation

1 Within one laborat ry

2 Between cooper g laboratories

3 Users of common data bank

4 Nation-wide requirements

B Criteria for Selection(8)

. 1 Specificity with accuracy'andprecision ,

5 Others

D Commonly -Used Types(8)

1 Various sample treatments (filtration,digestion. etc.)

2 Electrode-meters

3 General analytical methods

a Volumetric analysis

b Grav( inetric procedures

c Combustion

4 Photometric methods

a AtoMic absorption

b Flame emission

Colorimetry

5 Gas chromatography

E Selection on Basis of Use of Data

1' Compliance monitoring

a National Pollutant DischargeElimination System and. State

2 yaw:my established by sufficient Certif (cations( 10)use and evaluation

3 Equipment and skill requirements.normally available . .

4 Time requirement reasonable

C Sources

1 Annual BoOk of ASTM Standards(3)

2 Standard Methods fqr the ExaminatiOnof Water aftd"W'astewater(8)

5-2

"1) Use of alterni;te procedures '

2) Procedures for non - listed'paraineters

b National Interim Primary Drinking WaterRegulations!I I)

'1111

1) Use of alternate procedures

41

2) Procedures -for non-listedparameters

, Elements of a Quality Assurance Program

2 State monitoring progiams(12)'.

a Fixed station ambient monitoring

b Intensive survey programs

3 Local regulations .

4 Pre-survey field investigations

5 Control of treatment processes

F Using Recognized Procedures

I Written step-by-step laboratorymantles

2 Strict adherence to reference sour e

3 Record of modifications and why

CI Field Kits

I Shortcomings

2 Uses

IV CONTROL OF SERVICES, INSXRUMENTS,EQUIPMENT AND SUPPLIES'''

A Services

I Distilled water

a Ammonia-free

b Carbon dioxide-free

c Ion-free

d Low organic background

2 Compressed air

Dry

b Oil-free

c No contaminants

3 .Electrical service

a Adequate voltage

b Constant voltage

c Appropriate grounding

d' Efficient lighting.

B instruments

Applicable to laboratory and field instruments;and, as possible. fixed continuous monitoringdevices.

Written requirements for daily warm up,standardization, calibration: and/oroptimization procedures.

2 Standards available to perform daily checkprocedures.. Some examples;

a Standardized weights

b Certified thermometer

c Filter (or solution) for wavelengthalignment check

d Standlird reference materials withcurves

e Standar resistor ,

Calibration solutions (buffers; con:ductivity or turbidity standards)

g Parameter standards to establish orto cheek calibration curves

h. Radioactive standards with dateand count

Written trouble-shooting procedures.

.4 Schedule for required replacement orcleaning procedures

5 Schedule for check and or 'adjustments .

by service personnel

42 5-3

Elements ofa Quality Assurance Program

C Laboratory Equipment e Other laboratory operations likefiltration, ion exchange. absorption

1 Great variety and extractions may require specializedconstruction like fritted ware which has

a Of materials (glass. plastic, pressure and thermal shock limits.porcelain, etc. )

.13 Of grades

c Of accuracy in calibration

d Of specific properties

e Of unique construction

Z Selection depends on function

a Measurement and delivery ofvolumes require varying ,degrees of accuracy.

b St rage of reagents and solutionsnecessitates composition consider-

. ations such as:

3 Cleaning procedures

a Basis of selection

1) Appropriate for the compositionmaterial

2) Appropriate fOr materials to beremoved '

3) Appropriate for subsequent use -(Avoid introducing contaminants)

b Definite program

1) Standar:clized, consistent,mandatory

2) Analytical checks on effectiveness1) Polyethylene bottles for solu-

tions of boron, silica and D Laboratory Supplies - Reagents, Solv'entsalkali and Gas& I)

2) Glass containers for organics

3) Brown glass for light-sensitivesolutions

c Confinement of reactioits maypresent special requirementssuch as

I) Ground glass joints

2) Teflon plugs

3) Special resistance to thermalock

- 1

5-4

4) phsvious to digestionnditions '

d V umetric analyses involve:

1) Very accurately calibratedglasswitte

2) Consideration of the teinperatuareat which the apparatus wascalibrated

1 Required purity depends on:

a What is measured

b Sensitivity of method

c Specificity of detection system

2 General guides

If purity is not specified-in the method.some general guides are:

a General inorganic analyses

1) Analytical reagent (AR) gradechemicals. except.use primarystandard grade for standardizingsolutions.

2) Distilled water and solvents freeof constituent

3) Commercial grade gases

43

Elements of a Quality Assurance Program

b Metals analyses by flame

I) Spectroquality chemicals forstandards

Spectroquality recommendedfor other reagents and solvents,though analytical reagent grademay be satisfactory.

3) Acids should be distilled inglass.

4) De ionited distilled water

5) Commercial grade or laboratory-supplied gash

c Radiological analyses

11 Scintillation grade reagents andsolvents

. 2) High purity, extra dry gaseswith low radioactive background

d Organic analyses ,

1) Reference grade when available,AR at minimum

2) For gas chrothatography (GC).various detectors require absenceof certain classes of compounds,and may necessitate treatment

. of chemicals:

31 Pesticide quality. solventsFor GC. check assay.

4) Type of detector affects gas, quality required. Molecular-

sieve carrier -gas filters anddrying tubes are required oncombustion gases.

3 Program for assuring quality

a Written purity requirementsaccording to methods utilized

b Date all on receipt.

c Observe shelf life recommendations.Discard date on container

44

Observe appropriate storagerequirenients.

e Check assay for possible.interferences.

f Run reagent and solvent blanks.

g As applicable, check backgroundof reagents and solvents.

h Run method blinks (alPreagentsand solvents) with every series

' of samples or one for everynine samples.

Definite procedures for limitsof error, clean-up proceduresor application of correctionfactors

Replace gas cylinders at100-200 psi.

4 Procedures yor removing impurities

a Recrystaililation

b Precipitation

c Distillation

d Washing with solvent(s) used inanalysis

e Aging (gases)

f Others

5 Reagent and standard solutions

a Preparation

1) Use of primary standard gradechemicals as required

2) Careful weighing

3) Class A volumetric glassware

4) Appropriate quality distilledwater or solvent

5) Label listing compound(s),concentration, date of pre-paration or discard, preparer

6) Very dilute standards preparedat time of use

5-5


b Standardization as:appropriate..

1) Use reliable primary standards.

2) Restandardize as requfred bystability.

c Purchased solutions

1) Sh Ould contain-chearnicalsspecified by method

2) Should be checked foraccuracy

d Storage

1) Clean containers of materialsuitable for solution to bestored

2) Tight-fitting stoppers or 'caps

3) Safeguards against evaporationof solvent, adsorption of gasesand water vapor, effects oflight or temperature. etc.

e Signs of deterioration'

1) Discoloration

2) Forration of precipitates

3) Significant change inconcentration

V QUALITY ANALYTICAL PERFORMANCE")

A Skilled Analyst

1 Appropriate and continuing training

2 Willingness to follow specifiedprocedures

3 Skilled in manipulation of laboratoryequipment and techniques required

in analyses

4 Understanding of basic principlesUtilized and design of any instrumentss/he uses.'

5-645

Knowledge4ble and skilled in performingthe analyses for which responsible

6 Precision and accuracy performanceacceptable

B Establishing'Analyst Precision

Applicable except for gaschromato-graphy and radiological instrumentation.

1 Seven replicates of four samplescovering the concentration rangeof applicability for analysis

2 Test among routine samples overtwo hours or more in norneal operatingconditions.

3 Calculate the standard deviation foreach set.

4 Compare result to precision statementfor method in the source of the procedure.(It may be stated as % relative standarddeviation. If so. calculate analyst resultsin this form).

5 Individual's precision shduld be betterthan round-robin precision results.

C Establishing Analyst Accuracy.

Exceptions: giro chromatography andradiological instrumentation

1 Spike set of 7 precision replicates ofconcentration low in applicability rangeto bring final-to twice original.

2 Spike set of 7 precision replicates ofmid-range concentration to bring finalto about 75% of upper limit of applica-bility.

Test among routine samples over twohours or more in normal operatingconditions. ,

4 Calculate recovery fol^each set usingaverage of results from the precisioncheck and the recorded spike amounts.

5 compare result to accuracy statementfor method in the source of the plocedure.(It may be stated as bias, 1. e..

recovery- 100%.).


IndiAdual's accuracy should bebetter than round-robin accuracyresults. .

D Daily Performance Evaluation

1 At least two standards (high and low)analyzed with a blank to iferify anestablished standard curve (comparableoperating conditions)

2 Somi.methods require daily preparatibnof a standard curve.

3 o e of about every 10 samples shoulda duplicate to check precisionording to acceptable Standard

dev tion (or % relative std. deviation).

4 One o out cry 10 samples shouldbe a spiked samp to check accuracyaccording to acceptable % recovery(or % bias).

E Documentation of Daily Performance

I After 20 sets of duplicate data resultsor of spiked sample results have beencollected, control charts for precisionand accuracy, respectively, can beconstructed.

2 A variety of construction methods isavailable.

3 Plot succeeding results on theappropriate chart.

4 Charts document reliability of data.

5 Charts give signal of out-of-controlnumbers, trends toward out-of-controlconditions, improved performance,etc.

F Secondary Checks on Performance(2)

1 Quality Control samples are availablefrom.EPA at no charge for manycommonly-analyzed constituents.The concentration is provided withthe sample. These might be run

,every three to six months.

2 Run Split samples and compareresults with the other laboratory.

3 Run performance samples (unknowns)available from EPA at no charge.

4 Participate in round-robin method andperformance evaluation studies.

5 Participate in laboratory evaluationprograms.

yA

VI ATA HANDLING AND REPORTING(1)

must have a program for /systematic and uniform recording of Idata, and for processing and reportingit in proper form for interpretation andUse.

.

A. The Analytical Value

1' Correct calculation formulas reducedto simplest factors for quick, correctcalculations.

2 Provisions for cross-checking calculations

3 Rounding-off rules uniformly applied

4 Significant figures established foreach analysis

B Processing

Determine control chart ap proach andstatistical calculations required forquality assurance and report purposes.

2 Develop report forms to providecomplete data documentation andpermanent records, and also tofacilitate data processing,

a To avoid copying errors, the.number of forms should be minimal.

C Reporting

The program for data handling should providedata in the form/units required for reporting.

5-7

. Elements of a Quality AssuranCe Program

D Storage

1 For some types. of data: laboratoryrecords must be kept readily availableto regulatory agencies for a period oftime.

2 A bound notebook or preprinted dataforms permanently bound provide gooddocumentation:

3 STORET is a system for storage and ..retrieval of water quality data. It is 't

a State/Federal cooperative activitywhich provides States with direct accessinto the central computer system.

4 Many agencies have access to local.systems for storage and retrievalof data.

VII SAFETY CONSIDERATIONS(13)

A Laboratory Facilities

B Emergency Equipment

C Program for Health Checks as Required

D Program for Inventory and Cot .4'Toxic and Hazarilous Materials ,r.41Test Wastes

E Safety Officer-Pt sponsibilities

Informatics.

2 Planning

3 Inspection

4 Implementation

5 Evaluation

8 Reports

VIII EPA AQC Coordinators

A Each of tile ten EPA Ibgtona has anAnalytical Quality Control Coordinator.

5-8

1 Implements program in regionallaboratory

2- Maintains relations and serves assource of information for'state andinterstate agencies within the region

3 S es as liaison for EPA's EnvironmentalMon °ring and Support Laboratory (EMSL).

B- The nam address and telephone numberof the re nal AQC Coordiriatorcan beobtained .f m the EPA Regional Adminis-trator's floe or from EPA-EMSL.Cincinnat Ohio 40288.

IX. SUMMA

Quality Assurance regarding water quality(or any type of) laboratory data requiresplanning. control and checking for everyphase of the operation from sample collec-tion through storage of the data. Thisline contains a basic checklist of informationand items to be considered when'developinga program to facilitate quality analytical'performance by laboratory personnel.

To make the program effective, proceduresmust be written. responsibilities must beclearly defined and assigned, and individualsmust be accountable. Development and dailyperformance of such a program which meetsthe needs of an individual laboratory (oragency) will take time. Considering theimportance of the data produced, the inyest-ment in assuring its reliability is'a soundone.

REFEREES

1 cal Quality Control in Water andWastewater Laboratories. 1972. U: S. EPA-EMgL, Cincinnati, Ohio 45288.

2 Minimal Requirements for a Water QualityAssurance Program, EPA-440/9-75-010.U.S. EPA Office of Water Planning andStandards. Washington, D.C. 20480.

4 7 .

3 Annual Book of ASTM Standards (Part 311,Water. 1975. AmericanSociety for Testingand Materials. Philadelphia. PA.. 19103.

4 Handbook for Monitoring Industrial Waste-water, 1973. U.S. EPA-TechnologyTransfer. Cincinnati, Ohio 45288.

5 Standard Methods for the Examination ofWater and Wastewater. 14th edition: 1978,APHA-AWWA-WPCF, Washington. D. C.,20036.

6 Methods for Chemical Analysis of Waterand Wastes. 1974, U.S. EPA -EMSL..Cincinnati. Ohio 45288.


7 Model State Water Monitoring Program.EPA-440/9-74-002. U.S. EPA Office ofWater and Hazardous Materials: Washington.D. C.

8 U.S. Geological Sd'ivey Techniques ofWater Resources Inventory; Book 1, 1975;Book 5, Ch. Al. 1970; Bodk 5, Ch. A3, 1972; c,et. al. ; U.S. Government. Printing Office,Washington, D. C.. 20402,

9 K rr,ner, "Methodology kir Chemical Analysisof,Water and Wastewater" U.$, EPA-NTOTC.Cincinnati, Ohio one.

10 Federal Register, "Guidelines Establi.hingTest Procedures for the Analysis of.Pollutants", Vol. 41. No. 232, December 1.1978. pp 52780-52788.

.11 Federal Register," National Interim PrimaryDrinking Water Regulations," Vol. 40.No. 248. December 24, 1975. pp. 59588-59574.

:2 Federal Register, "State and LocalAssistance." Vol. 41. No. 82. April 27,1976 pp. 17894.17700.

13 Safety Management Manual. 1972U. S. EPA. Washington,-D.C. 20480

This outline was prepared by Audrey D.Kroner, Chemist. National Training andOperational Technology Center. MOTU.OWPO, USEPA, Cincinnati. Onio 45268

DESCRIPTORS: Analytical Techniques.Chemical Analyses. Quality Assurance,Quality Control. Reliability. Water Analysts

5-9

VOLUMETRIC ANALYSIS OF WATER QUALITY

I INTRODUCTION

A A standard solution is one whose com-position and concentration are knownto a high degree of accuracy. In chem-ical analyses, it is used to determinethe concentration of a particular corn-ponent in a sample.

a These chemical analyses very frequentlyinvolve an acid-base reaction or anoxidation-redubtion reaction.

C Three imporiant terms connected withthese two types of chemical reactionsare: mole, equivalent weight, a Idnormality. These terms will be de-fined in following sections.

II ANALYTICAL CHEMICAL REACTIONS

A fe,seat..4,,Ltbove, in a chemical analysis-"`"it volume oittandard solution is brought

into contact with a volume of samplein order to determine the concentrationof some particular component of thesample.

B For a given volume of sample, it isnecessary to use a definite amount ofthe standard solution--too much.or toolittle would give erroneous results.

C For example, one cannot simply mix'together random volumes of sodiumhydroxide and hydrochloric acid solu-tions and expect the only two substancesproduced to be sodium chloride andwa

D Unless the concentrations of the t woreagents are known and the amountsmeasured accurately, excess sodiumhydroxide or hydrochloric acid willalso remain at the end of the reaction.

E The reason for.these limitations isthat when molecules react withone another, they do so in definite ratio.

PC. 17b. 11.77

Unless the number of molecules of eachreactant is known, there willalways bean excess of one of the reactants re-maining at the end of the chemicalreaction. As mentioned before, thisleads to erroneous analytical results.

F . Because of their size, it is not possibleto count out numbers of molecules.However, the number of molecules ina quantity of a chemical may be found

,by determining its weight and consultinga table which lists the'weights of theatoms making up the chemical.

G For example, sodium hydroxide has theformula NaOH. It can also be statedthat a molecule of sodium hydroxideconsists of one sodium atom, one hy-drogen atom and one oxygen atom.

One sodium atom weighs 23 atomicmass units (amu). An oxygen atomweighs 16 amu; and a hydrogen atomweighs 1 amu.

A molecule of sodium hydroxide, there-'fore, weighs 40 amu; all amu valueshave been rounded off. Forty amu isthe molecular weight of sodium hydroxide.

H A mole of any chemical is anumber ofgrams numerically equal to the molec-ular weight of that chemical. One moleof sodium hydroxide, therefore, con-tains 40 grams (40 g).

I Similarly, the atomic w eight of achlorine atom is 35minu; that of a hy-drogen atom is 1 amu; and the molec-ular.weight of the hydrogen chloridemolecule is 36 amu. One mole of hy-drogen 'chloride weighs 36

J Synonyms for mole are: mol, grammol, gram mole, and gram molecularweight.

K Tables listing atomic weights of theelements can be found in virtually all

'436-1

Volumetric Analysis of Water Quality

of the texts used for high school andfirst year college chemistry courses.

L The remaining two terms mentioned inIC (equivalent weight and normality).will be considered as they are related toacid -base and oxidation-reduction reac-tions.

III ACID-BASE REACTIONS

A Recall that an acid is a substance whichdonates a hydrogen ion, or proton, (H+)in a chemical reaction and a base is asubstance which donates a hydroxide ion(OH-) in a chemical reaction. Reactionsinvolving these two ions are termedacid-base reactions.

B In the case of sodium_byggoxide, themolecular weight is 40ramu an d onemole of sodium hydroxide weighs 40 g:One hydroxide ion is contained in thesodium hydroxide molecule.

1 For a base, the number of gramsin a mole divided by the number ofhydroxide ions equals a quantitycalled the equivalent weight. Ex-

.- amplea are ,given below. All amu ,values have been rounded off.

i 8 -2

a Base -potassium hydroxide KOH

Atoms Number. Wt/atom TotalK 1 39 amu 39 amuO 1 16 16H 1 1 1

56 amuOne mole of KOH 56 gNumber of hydroxide ions 1

Equivalent weight of KOH 56 g

b Base -magnesium hydroxideMk(OH)2

Atoms Number Wt/atom TotalMg 1 24 amu 24 amuO 2 16 32H '.2 1 2

58 amuOne mole of Mg(OH)2 58 g .

Number of hydroxide ions 2Equivalent weight of Mg(OH)2 29 g

2 For an acid, the number of gramsin a mole divided by the number ofhydrogen ions is the equivalentweight, Examples are given below.All amu values have been roundedoff.

a Acid - nitric acid HNO3Atoms Number Wt/atom

H 1 1 amuN 1 14O 3 16

One mole of HNO3 63 gNumber of hydrogen ions 1

Equivalent weight of HNO3 63 g

b Acid - sulfuric acid H2504

Total1 aini

144863 amu

Atoms Number Wt /atomH 2 1 amuS 1 32O 4 16

Total2 emu

326498 amu

One mole of 112504 98 gNumber of hydrogen ions 2Equivalent weight of H2SO4 49 g

Normality is a method of expressingsolution concentrations. If one equiv-alent weight of a chemical is dissolvedin a solvent and the volume brought toone liter (1), the concentration of thesolution is one normal (N).

1 The equivalent weight of KOH wascalculated to be 56 g. This amountof the solid dissolved in water anddiluted to a liter would give a INsolution.

2 The equivalent weight of HNO3 wasfound to be 63 g. This quantity ofacid diluted to a liter would give aIN solution.

IV OXIDATION-REDUCTION REACTIONS

A The concepts of mole, equivalent weightand normality, as described in previoussections, apply also to oxidation-reduction reactions.

50

Volumetric Analysis of Water Quality'

B One definition of an oxidation is that itinvolves an increase in the oxidationstate (charge) of an atom.

For example: FeC12 - FeC13. In thisconversion the Fe has been oxidizedfrom +2 to +3,

C A reduction is a decrease in the oxida-tion state (charge) of an atom.

For example: KMnO4 Mii02. In thisconversion the Mn has been reducedfrom,+7 to +4.

, The equivalent weight of an oxidizingOr reducing agent is calculated bydividing the number of grams in a moleof the reagent by the change in chargeinvolved.

For example: FeC12 (used as a reducingagent).

Atoms NumberFe 1

Cl 2

Wt /atom Total56 emu 56 arnu70 70

126 amuOne mole of FeC12 126.gChange in charge 1

Equivalent weight of FeC12 126

The concentration of a liter of solutionwhich contains 126 g of FeC12 is 1N.:

V PRIMARY STANDARDS

A A reagent of known purity is called aprimary standard. Primary standardgrade chemicals are available fromchemical supply houses and the NationalBureau of Standards. An accuratelymeasured quantity of a primary stand-ard is used for the preparation ofstandard solutions.

B Other requirements of a primary stand-are are:

1 It must be stable at 105°C (thetemperature used for drying).

2 It should not be reactive with com-ponents of the air, such as 02 andCO2.

3 It.should have a high equivalentweight so as to minimize anyerrors in the analysis.

4 It should be readily available at areasonable cost.

VI STORAGE OF STANDARD SOLUTIONS

A Standard solutions should be prepareduaing high quality distilled water.

B Care should be taken to insure thecleanliness of the glass or plasticbottle used for storage.

C Some solutions may decompose onex-posure to light and should be stored indark bottles.

D The stopper or cap should fit tightly.

VII CALCULATIONS ,

A The basic formula used in volumetricanalysis is

XN) of standard solution(1 XN) of sample

In atypical analysis. three of the fourquantities are known, or found, and

N of sample (1 XN) of standard1 of sample

B This formula can be rearranged to sixg 1 XN X'evtvalent weight .IP,

where g and equivalent weight (ew) re-fer to the component being analyzedand 1 and N to the standard solution.

C For-example: How many g of NaQH arepresent in a sample if 100.0 ml of 0.2NHCLare required for its titration?

g 1 XN X equivalent weight

100.0 ml 40. 0X0. 2 X- 0.81000.0 ml 1 1

5.1

6-3

Volumetric Analysis of Water Quality

REFERENCES

1 Hamilton, St B. and Simpson, S. G.Quantitative Chemical Analysis11th edition, The MacMillan Co..New York. 1958.

2 Blaedel, W. J. and Meloche, V. W.Elementary Quantitative Analysis:Theory and Practice. Row,Peterson and Co., N.Y. 1957.

6-4

3 Ayres, G. H. Quantitative ChemicalAnalysis. Harper and Brothers,New York. 1958.

This outline was prepared by C. R. Feldmann,Chemist. National Training and OperationalTechnology Center, MOTD, OWPO, USEPA,Cincinnati, Ohio 45268

Descriptors:Analytical Techniques. ChemicalAnalysis. Volumetric Analysis, WaterAnalysts

0

52

ACIDITY, ALKALINITY, pH AND BUFFERS

DEFINITIONS OF ACIDS AND BASES

Arrhenius Theory of Acids and Bases(Developed about 1887)

1 Acid: A substance which produces,in aqueous solution, a hydrkenion(proton),

.2 Base: A substance which produces,in aqueous solution, a hydrcixide,ion, OH-.

3 The A rrhenius theory was confinedto the use of. ater as a solvent.

B Bronsted and Lowry Theory of Acidsand Bases (Developed about'1923)

I Acid: A substance which donates*,in chemical reaction, a hydrogen

ion (proton).

C

II

A

Br

2 Base: A substance which accepts,in chemical reaction, a hydrogenion (proton).

3 Bronsted'and Lowry had expandedthe acid-baseconcept into non-aqueous media; 1,e., the solventcould, but didnot have to be,water,

There are other acid-bise theories. Thetwo above are probably the most commonlyused ones when discussing wastewatertopics however. se

DEFINITIONS OF ACIDITY,ALKALINITY AND NEUTRALITY.

A cidity

'A 'condition in which there is a prepon-derance of acid, materials present 1nthe water.

AlkalinityA condition in which there is lea peepon-derance of alkaline (or basic)materials'present in the water.

CH. A /IC. 3. 11.77

C . Neutrality

1 It is possible to have present inthe water chemically equivalentamounts of acids and bases. Thewater would then be deitcribed asbeing neutral; e., there is apreponderance of neither acid norbasic materials. The occurrenceof such a condition would be rare.

2 The term "neutralization" refers tothe' combining of chemically equiv-alent amounts of acids and bases.The two products of neutralizationare a salt and water.

HCl t NaOH

Hydro- Sodiunichloric Hydroxideacid

NaC1 + H2O

SodiumChloride

(a salt)

D . The key word in the above definitionsis "preponderance," It is possible to

. have a bas ion of acidity while thereare basic materials present 'in thewater, as well as conversely.

III HOW ARE DEGREES OF ACIDITYANDALKALINITY EXPRESSED?

The plrecale is used to express variousdegrees of acidity and alkalinity. Valuescan range from 0 to 19. These two ex-tremes are of theoretical interest and wouldnever ,be encountered in a natural water orin a wastewater; pH readings from 0 to.just under 7 indicate an acidif condition;from just over 7 to 19,1hat alkaline condition.Neutrality exists if the value is exactly7. pH paper, or a pH meter, provides themostconvenient method of obtaining pHreadings. It should be noted, thatunder 19PDESMethodology. pH measurements are to be madeusing a pH meter. Sonie common liquids and pHvalues are listed in Table I.

*National Pollutant DischargeElimination system..

53

7-1

Acidity, Alkalinity. pH and Buffers

'TABLE 1., pH Values of Common Liquids

Household lye 13.7Bleach 12.7Ammonia 11.3Milk of magnesia 10.2Borax 9.2Baking soda 8.3Sea water 8.0Blood 7.3Distilled water 7. 0Milk 6. 8Corn 6.2Boric acid 5.0Orange juice 4.2Vinegar 2.8Lemon juice 2. 2Battery acid 0.2

5.9 - 8.4 is the common pH range for moenatural waters.

IV HARD AND SOFT WATERS

'in addition to being acidic or basic, watercan also be described as being hardor soft.

A Hard water contains large amounts ofcalcium, magnesium, strontium, man- .ganese and iron ions, relative to theamount of sodium and potassium ionspresent. Hard water is objectionablebecauseit forms insoluble compoundswith ordinttry soap.

B Soft water contains small amounts ofcalcium, magnesium, strontium, man-ganese and iron ions, relative to theamount of sodium and potassium ionspresent. Soft water does not form in-soluble compounds with drdinary soap. ,

TITRATIONS

A The conversion of pH readings into suchquantities as milligrams (mg of acidity,alkalinity, or hardness, is nqk easilycarried out. These values are Moreeasily obtained by means of.a titration.

B In a titration, an accurately measuredvolume of ;ample (of unknown strength)is combined with an accurately measured

. .

z

7-2

volume of standard solutio'n (of knownstrength) in the presence of &suitableindicator.

C The strength (called normality) of Thesample is then found using the followingexprestion:

milliliters (ml) of sample X es:n*8114(N) of sample ml of standard solu-tion X N of etandard...solution,

Three of the four quantities are known,and

r N of sample ml of standard solutionX N of standard solution/ml of sample.

D In Modified form, and a more specific .

application of the above equation, allot-' Unity is calculated in the following

manner (13th ed. Standard Methods).

mg of alkalinity as mg CaCO3/liter (1)ml of standard ii2SO4 X N of standard

H2504 X 50 X 1000 /ml sample.

VI INDICATORS

The term "suitable indicator" was u se aabove. At the end of atitration. the pH ofthe solution will npt necessarily be 7. Itmay be above or below 7. A suitable inoi-cator, therefore; is one which undergoesits characteristic color change at the appro-priate pH, Below are a few, examples ofindicators and the pH range in which theyundergo their characteristic color changes.In some cases, mixed indicators may beused in order to obtain a. sharper and moredefinite color change. Again it should be noted

yipat under NPDES. pH meters are tohe usedr the measurement of pH. ,

Indicator .

OperationalpH Range

Methyl YellowMethyl Orange

2. 8 - 4.03. I - 4.4

Methyl Red 4.4 - 6.2Cresol Purple 7.4 - 9.0Phenolphthalein 8.0 - 9.6Alisarine Yellow 10.0 - 12.0

TABLE 2. pH Rana of Indicators

54.

ACidity, Alkalinity, pH and -Buffers.

VII BUFFERS

A A buffer is a combination of substanceswhich, when dissolved inwater, resistsk pH change in the water, as might becaused by the additionof acid or alkali.Listed below are a few Chemicalswhich, when combined in the properproportions, win tend to maintain thepH in the indicated t.nge.

Chemicals pH Range

Acetic Acid + Sodium Acetate 3:7 - 5.6

Sodium Dihydrogen Phosphate. +Disodium Hydrogen Phosphate 5.8 - 8.0Boric Acid + Borax 6.8 - 9.2

Borax + SodiumHydroxide 9.2 - 11.0

'TABLE 3. HRan e of Buffers

B A buffer functions by supplying ionswhich will react with hydrogenlons(acid "spill "),, or with hydroxide ions(alkali "spill").

C In many instances, the buffer is composedof a weak acid and a salof the weak acid;e.g., acetic acid and sodium,acetate.

1 In water, acetic acid ionizes or"breaks down" into hydrogen ionsand acetate ions.

'HC21-1302 6 H+ + C2H302-(acetic acid) (hydrogen ion) (acetate ion)

tproton

This ionization occurs to only aslight extent, however, most of theacetic ack! remains in the form of'HC2H302; only a small amount ofhydrogen and acetate ions is formed.

2 Thus, acetic acid is Said to be aWeak acid.

3 In the case of other acids, ionizationinto the component ions occurs to a

large degree, and the term strong acidis applied; e.g., hydrochloric acid.

HC1 " Fe + C1-(hydrochloric (hydrogen ion) (chloride

acid) (proton) ion)

53

4 The terms and "weak" arealso applies to bases. In watersolutions, those which break downinto their component ions to a largeextent are termed "strong"; andthose which do not are "weak".Sodium hydroxide is a relativelystrong base, while ammoniumhydroxide is realtively weak.

5 Sodium acetate (a salt of acetic acid)dissociates or "breaks do, i" intosodium ions and acetate ions whenplaced in water.

NaC2H3O2 Na+ + C2H302-

(sodium acetate) (sodium ion) (acetate ion)

This dissociation occurs toa large. extent, and practically all of the

sodium acetate is in the iorm ofsodium ions and acetate ions.

D it would be difficult and expensive toprepare large quantities of buffers foruse in a treatment plant. However,certain naturally occurring buffers maybe available (carbon dioxide is an ex-ample). It dissolver in water to formthe species indicated below.

CO2 + H2O H2CO3(carbon dioxide) (Water) (carbonic acid)

H2CO3 H+ + HCO3(hydrogen ion) (hydrogen car-

(proton) bonate ion)(bicarbonate)

The hydrogen ions react with hydroxideions which might appear in the wateras the result of an alkali "spill".

+ OW H2O(in the (hydroxide ionbuffer) "spilled")

The hydrogen carbonate ions react withhydrogen ions which might appear inthe water as the result of an acid "spill".

H+ + HCO3" 1I2CO3(hydrogen ion) (in the(proton) buffer)"spilled"

This buffering action will be in effectaslong. as there is carbonic acid present.

7-3

Acidity. Alkalinity, pH and Buffers

Burering action is not identical witha process in whin acid wastes are':netitra:izA" with alkali wastes. orcor.dersely. The desired effect is c

achieved in bot.. cases, however (i.e.,the pH is ...aintained within a desiredrange.)

7-4

This outline was prepared by C. R.Feldmann. Chemist, National Training andOperational Technoldgy Center, MOTELOWPO, USEPA, Cincinnati, Ohio 45268, .

Descriptors: Acids, Acidity, Alkalis,Alkalinity. Analytical Techniques. Buffers,Buffering Capacity, Chemical Analysis,Hydrogen Ion Concentration, Indicators,Neutralization, Water Analysis.

53

A LKA UNITY AND RELATIONSHIPS AMONG THEVARIOUS TYPES OP A L/CA UNITIES

I PRELIMINARY

The property of water referred to as alkalinityis usually caused by the presence of hydroxyl.carbonate and bicarbonate ions. To a-lesserextent, borates, phosphates and silicatescontribute but are generally present innegligible amounts.

The concentration and ratio of the OH , CO3.and HCO3 ions may be measured by titratinga sample to certain specified pH's or endpoints which are detected either by use of apH meter or by color indicators. Phenol-phthalein is used for visual detection of thefirst end point, (approximately pH 8) whichindicates the neutralization of NaOH and con-version of CO3 to HCO 3 . A number ofindicators (methyl orange, methyl purple.brom cresol green.etc.) are used for detectionof the second end point (pH 3-5) which indicatesthe complete conversion of HCO3 to H,0 andCO2. The final endpoint is determineor bythe a mount of CO3 and HCO3 originallypresent in the sample. lf the end points aredetermined electrometrically they are takenas the mid-point of the greatest rate of pHchange per unit volume of titrant.

II RELATIONSHIPS BETWEEN HYDROXIDE,CARBONATE, AND BICARBONATEALKALINITIES

The results obtained from phenolphthaleinand total alkalinity measurements offer a

.means of classification of the principalforms of alkalinity, if certain assumptionsare made. It must first be assumed thatinterferences are absent and that bicar-bonate and hydroxide do not exist in thesame solution. According to the system

presented in Standard Methods(11

A Hydroxide alkalinity is present if thephenolphthalein alkalinity is more thanone-half the total alkalinity,

B Carbonate alkalinity is present if thephenolphthalein alkalinity is not zerobut is less than the total alkalinity.

C Bicarbonate alkalinity is present if the-phenolphthalein'aUcalinity is less thanone-half the total alkalinity.

Table 1. Relationships Between Phenolphthalein Alkalinity, Total Alkalinity,Carbonate Alkalinit . Bicarbonate Alkalinity

-OH Alkaltnityas CaCO3

and Hydroxide Alkalinity,. CO, Alkalinity

as taCO3HCO, Alkalinityas 01CO3

Lectui:eNotes

Result ofTitration .

Fase 1

Case 2

Case 3

Case 4

Case 5

P TP . iTP 0P > ITP < iT

T

00 .

2P-T0

02P

02(T-P)

2P

00T

0T-2P

P Phenolphthalein Alkalinity

5 '7

T Total AlkaliniiY.

8-1

Alkalinity and Relationships Among the Various Types of AP,e14flitiAs

Table 2. Stoichiometric Volumes of Solutions of Different Normalities

Standard Solution H2

SO4 NaOH Na 2CO3 NaHCO3

Normality 0.0200 0.0189 0.0199 0.0125

Equivalbnt Volumes, ml 10.0 10.6 9.9 18.0

9.4 10.0 .9.5 15.1

10.0 10.5 10.0 4.96.3 ' 6.6 6.3 10.0

III CASE EXAMPLES

The relationships involved in Table 1 maybest be explained by reference to the followinggraphs. These were prepared by titratingvolumes of standard solutions of sodiumhydroxide, sodium carbonate, and sodiumbicarbonate with standard sulfuric acid. 'The etoichiometric volumes of the varioussolutions are summarized in Table 2 forconvenience in the interpretation of the charts.

A CASE 1 - Where phenolphthalein alkalinitytotal alkalinity

MI ...MI., 11,404 4/110.:11

Y.1111 egArr

The sharp break occurs at the point whereall of,the NaOH has been exactly neutral-ized by the acid. The pH and concentrationof the end products (Na SO4 and H

2O)

determine the pH at thAreqtAvalende pointbetween NaOH and H2504; in this case,approximately 7.0.

8 -2

B CASE 2 - Where phenolphthalein alkalinityone-half the total alkalinity

Jip ,MI, 0,0, A 11,1.m..

or

The titration eroceeds in 2 stages wherein .all of the CO,, is converted, first toHCO3 and Arany to /12C09 . The firstend point occurs at approximately pH 8,and at exactly half the volume of acidused for ,.thaittal titration. The end pointwhich oc t approximately pH 4represents alkalinity and requires

/ICctly twice the volume of acid used forfirst end point.

If either HCO; or OH ions had beenpresent the titration volumes for the curveswould not have been of equal magnitude.

53

Apalinity and RelationsWs Among the Various Types of Alkalinities

C CASE 3 - Where phenolphthalein alkalinity= 0

T The reaction proCeeds in one stage withthe initial pH at approximately 8.5 andfinal pH at 4.0. In this case the phenol-phthalein alkalinity is zero and since noconversion of b03.- to HCO3 is noted thetotal alkalinity can only be due to theHCO3 ion.

D CASE 4 - Where phenolphthalein alkalinityis greater thz one-half the total alkalinity

The volume of acid required for the firstend point (phenolphthalein alkalinity) isdue to the OH neutralization and con-version of the CO3 to HCO, The .

Sc , end end point represents the complete,nversion of HCO3 to ReferringCase 2 where the voluare of acid was

similar for each send point, it is apparcntthat a base responding to phenolphthaleinbut which is not CO, must be present,Since it was originally assumed that OHand HCO3 do not exist in the samesolution we muit conclodethat the totalalkslinity is due to OH and 'CO3 .

E CASE 5 - Where phenolphthalein alkalinity.is less than one half of the total alluzlzaity

53

,;..

111.1 Nis 1,11.../

If, in the reactionia0H + NaHCO3-Na CO + H00, the NaOH existsexcess quantity, the final sample con-tains NaOH and NaCO3, (Case 4) inwhich the volume a acrd required forthe phenolphthalein end point is greaterthan one half the total. In this case,however, the situation is reversed,wherein the, volume of acid requiredfor the HOO, end point is greater thanone half the "total. Referring again tothe reaction NaOH + NaHCO3 - Na

2CO3 +H2O, if NaHCO

3in excess the end

products must consist of Na2CO, andNaHCO

3and OH must be absent. The

end points consist, therefore, of Na CO3NaHCO (phenolphthalein end potht)

Crand NaHC H2CO

3 3'

8

"Alkalinity and Relationships Among the Various Types of Alkaiteitis

F CASE 6 - Where phenolphthalein alkalinityis greater than one-half totalillialinity,

111 41 14 ICI

ir :

Following the original assumption that0/1" and HCO 3" are not compatible, withHCO 3" being converted to CO3 we havea dondition7similar to Case 4 (F > IT).

G CASE 7 - Where phenolphthalein alkalinityis greater than ohe-half total alkalinity.

20 2i VI

IA 14 0 PIO IVE..1...o., . xrx 1131/20 x finf.11 III tall.

.1.1112i 3..

Th. firsLend point occurs at the stoichio-metric sum of the equivalent volumes asfollows:

(9.4 - 6.3) + (10 + 12.6)2

where (9.4 - 6.3) volume of N acidrequired for excess OH after OH +HCO3 reaction,

(10 -I216 . volume of acid required

for ,conversiod of CO, to HCO3 . Thesecond end point occdrs at10 + 12.6) -mle the volume of HCO3

2which is converted to H,C0. This thenbecomes thrsame as Case 4.

IV COMPARISON OF ANALYTICALMETHODS FOR ALKALINITY (Accordingto the Analytical Reference Service

,Report JAWWA Vol. 55, No. 5, 1963)

M.73101 0115.111001100 IMAM

TAKE 7-SAW Ammo., (w A)

Comm Oro:.,mol

t7r =foryA I...1 Low 2.

AAA map 1970 A 19 20.0 1113 53.0 a 2 5.04919391961

1927

1742.5

1934.17

II30

24SO

0 I01.7

1.4013.130

1304.04 19311

1939.1433

1917

19.7194

/90IS

21.013

0 10 2

0.9111.740

03011 PA 91119411936

ISI 41.319

44.114.7

31914.0

5715.1

01.7a 4

3.6050.475

I9551%1

1019

17413

191443

IS40

SI50

* 2013

00333A1

AI% iVal42.0/ Ma1914 15

17413

19.3413

ISA

A49

* 3a 3

IMO3.350

Dras and en%MI .4414414

19391934

I40

1719

19191

1911

19A.0

a 2a 2 4.460

19391961

911711

17414

1144.1.9

1523

3357

* 2 1320* 1.9 5.135

Allralilty - The methods for alkalinitymeasurement varied only in the choiceof indicator or pH for determining the e

end point of the'titration. The indicatorsused included methyl orange, methylpurple, and mixed indicator. The data!bows that as the use of electrometricend point increased, the use of methyylorange decreased.

"

Alkalinrcy'and Relationships Among the Various Types of Alkalinities

SUMMARY

Amount Added

Avg. Deviation fromamount added

Standard Deviation

.50% Range ;Method Most Comthon lyUsed

Method Preferred

Total NUmber'ofObservations

17 mg/1 (as Ca Ogy

3. 1 mg/1

3.4 mgil2.0 mg/1.Electrometric

Electrometric

41

V PROCEDURE

very simple procedure requiring only titrationThe actual measurement of alkalinity is a

of sample with a standardized acid and theproper Indicator. For phenolphthaleinalkalinity the end point and indicator are wellestablished. For the biCarbonate titrationthe final end point is a function of the HCO3concentration. With low amounts (<50 mg/1as CAC0,) the pH at end poir.t may bdapproxinfately 5.0. With high concentrations(>250 mg/las C.aC0,1 the pH at end point maybe 4.5 to 3.8. For ill-purpose work, inwliicitthe highest degree of accuracy is notrequired, an end point at pH 4.5 using methylpurple as the indicator is recommended.

The traditional methyl orange frequentlyproves to be unsatisfactory because of theindefinite color change at the end point andalso because of the low pH (3.8 - 3.9)required to establish the change.

4

VI EPA ANALYTICAL METHODS

A The Environmental Protection Agency,Office of Water Programs, has compileda manual of Analytical Methods which is tobe used in Federal laboratories for thechemical analysis of water and waste samples.The title of this manual is "Methods for

Chemical Analysis of Water and Wastes. ''(2)

B B This manual lists two parameters whichare related to the subject matter in thisoutline. They are total alkalinity andtotal acidity.

..

d C For the measurement of both of theseparameters. the recommended methodis volumetric. with the equivalence pointbeing determined elecirometrically.The use of a color indicator (methyl orange)is recommended omy for the automatedmethod.,

---s ,.....

REFERENCES

1 Standards . ethods for the Examination ofWater and Wastewater, 14th Ed.APliA, Inc., New York. 1978

2 Methods for Chemical Analysis of Waterand Wastes, EPA-MDQARL, Cincinnati,Ohio 45b8a, 1974.

This outline was prepared by R. C. Yeutter, formerChief, Physical and Chemical Methods.Analytical Quality Control Laboratory, NationalEnvironmental R h Center, Cincinnati,.

Ohio 45288..

Descriptors: Alkalis. Alkalinity, AnalyticalTechniques, Buffers, Buffering Capacity,Chemical Analysis, Water Anal/sin

Cl8-5

DETERMINATION OF CALCIUM AND MAGNESIUM HARDNESS

I INTRODUCTION

A Definition of Hardness

tSPHS - natural waters, hardnessis a characteristic of water which re- rpresents the total concentration of Justthe calcium andthagnesium ions ex-pressed as calcium carbonate. Ifpresent in significant amounts. otterhardness-producing metallic ions shouldbe included."

B Other Definitions in Use .

Smile confusion. exists in understandingthe concept of hardness as n result ofseveral definitions presently.used.

2 Soap hardness definition includes hy-drogen ion because it has the capacityto precipitate soap. Present definition

. excludes hydrogen ion because it is notcdnsidered metallic.

3 Other agencies define hardness as"the property attributable to presenceof alkaline- earths ":-

USPHS definition is best in relationto objections of hardness in aster.

II CAUSES OF HARDNESS IN WATERS OFVARIOUS REGIONS OF THE U. S.

A Hardness will vary throughout the countrydepending on:

1 Leaching action of water traversingover and through various'types ofgeological formations.

2 -Discharge of,industrial and domeaticwastes to water courses.

3 Uses of water which result in changeIn hardness, such as irrigation andwater softening process.

CH. HAR. 3e. 11.77

k

62

B Objections to Hardness

1 Soap - destroying properties

2 Scale formation

C Removal and Control

Hardness may be removed and controlledthrough the use of various softening oper-ations such as zeolite. lime-soda, andhot phosphate processes. It can alscberemoved by simple distillation or com-plex formatiowith surface active agents(detergents).

III ANALYTICAL PROCEDURES

A National Pollutant Discharge EliminationSystem (NPDES)

Under the NPDES of the 1972-Federal WaterPollution Control Act Amendments, analysesare to be performed using "approved"analytical procedures cited in the FederalRegister Guidelines Establishing TestProcedures for the Analysis ofPollutants. The cited proc0)edures arefound in Standard Mithods, AnnualBook of ASTM Standards(2). and Methodsfor Chemical Analysis of Water andWastea("). The three relevant para-meters are total hardness. expressedas mg Ca EO.aliter, total and dissolvedcalcium, and 'total and dissolved mag-nesium, all expressed in mg/1.

B Total Hardness, as mg CaC0311. .

1 Total hardness may be determined bytitrating the buffered sample withethylenedlamine tetreacetic acidAEDTA1at a pH of 10.0± O. 1 using a dye suckas Eriochrome Black T indicator.A color change from blue to red is theend-point. Either daylight or afluorescent lAinp should be used forillumination. Incandescent lights pro-duce a reddish tinglat the end-poiht.Certain metals such as iron, manganese.nickel, zinc and others, interfere withend-point clarity.

.9-1

!),terminatton of Cll. ium aid Magnesium Hardness

Chemical inhibitors are needed to tieup the interferring metals. Someinhibitors contain sodium cyanide, andextreme caution must be observed whenthey are used.

: In the automated procedure. magnesiur*EDTA exchanges magnesium for calcium.The released magnesium. plus the marnesium already present in the sample.produces a red violet complex with cal-magite at a pH of 10. The total hardness(i.e.. ralcium plus magnesium) is deter-mined therefore, by analysis for magnesium.

otgesti,... I

When determining Total Calcium or Totals.lagnesium, the initial step is digestion.The sample is first acidified with condentrai-ed redistilled HNO3(5 m1/1).. Five ml ofdistilled.HC1(50% by volume) are next addedto 100 ml of the well-mixed acidified sample.which Is heated at 95°C for 15 minutes.The sampl, is next diluted back to 100 mlfor analysts.

D Total Calcium. mg/1

1 Total calcium may also be determinedby titration with EDTA. at a pH of 12-13.Murexide. Eriochrome Blue Black B.and Solochrome Dark Blue are among theindicators which may be used. Thetitration should be carried outimmediately after raising the pH.Lower concentrations (e. g.. less than20 mg/1) of certain metals such ascopper. ferric and ferrous iron.manginese and zinc do not interfere.However orthophosphate precipitatescalcium at the elevated pH of the test.Strontium and barium interfere, andalkalinity greater than 30 mg/1 causesan indistinct end-point.

2 Lanthanumis used to mask thephosphate. sulfate and alcminuminterference in the atomic absorptiondetermination of calcium. High con-centrations (up to 500 mg/1) of sodium,potassium., and nitrate cause nodifficulty. Magnesium levels greaterthan 1000 mg/1 cause low results.

9-2

E Total Magnesium, mg /1

1 The gravimetric determination ofmagnesium involves addition ofdiarnmonium hydrogen phosphatewhich precipitated magnesiumammonium phosphate. The precipitat,is ignited and weighed ac magnesiumpyrophosphate. The sample shOuld bereasonably free of aluminum. calciursiron. manganese. silica, strontium.and suspended matter.

2 Aluminum concentrations greaterthan 2 mg/1 interfere with theatomic absorption procedure.Lanthanum is used as a maskingagent. At concentrations lessthan 400 mg/1. sodium, potassiumand calcium cause no problem

63

F Dissolved Calcium A. Dtssolved Magnesium.ntral

The dissolved.metals are determined by 0.45m filtration. followed by acidification with

redistilled HNO3 to a pH of 2, and the method(except for digestion) used for the "Total"metal. Pre-filtration to remove larger sus-pended solids is permissable. A glass enplastic filtration apparatus is recommendedto avoid contaminalon.

,ither Procedures

I The analytical procedures for totalhardness, calcium and magnesiumoutlined above are, those to be performedunder the NPDES.

2 Examples of other. "non-NPDES"procedures area Gravimetric determination of calcium.

b Potassium permanganate titrationof calcium.

c Determination of total hardness andcalcium or magnesium and then sub-tracting to obtain the concentrationof the other metal. This procedureassumes that calcium and magnesiumare the only hardness componentspresent.

d Determining the concentration of theindividual metals, multiplying theconcentrations by an appropriate factorto put the values on a calcium carbonatebasis, and then summing the calciumcarbonate concentrations to obtain atotal hardness value.

Determir.ation of Calcium and Magnesium Hardness

REFERENCES

I Standard Methods for the EXP .nof Water and Wastewater. 14th t.d.APH.A. AWWA, WPCF. 1976.

2 Annual Book of ASTM Standards.Pdrt 31. t9.75.

3 Methods for thetric.alWaterand Wastes. EPA ,,ISLCincinnati. Ohio 45268. 1974.

4 Barnard. A. J. Jr.. Broad, N. C. andFlaschka. H. The EDTA T.iration,J. T. Baker Company. 1957.

5 U. S. Public Health Service. DrinkingWater Standards. USPHS Report.Volume 61. No. 11. 1946;

6 Rainwater, R. H. and Thatcher. L. L.Methods for the Collection and Anal-ysis of Water Samples. U. S. Geo-logical Survey Water Supply, Paper1454. 1960;

7 Federal Register. Wednesday. Dec. 1. 1976.Part II. Table 1. footnote 17.

This outline was prepared by B. V. Salotto,Research Chemist. Waste Identification andAnalysis Section. MERL, EPA. and revisedby C. H. Feldmann. Chernist. NationalTraining and Operational Technology Center.MOTD. OWPO, USEPA, Cincinnati, Ohio45268.

Descriptors: Calcium. Chemical Analysis,. Hardness. NIXgnesium, Water Analysis.

Calcium Carbonate, Calcium Compounds.Magnesium Carbonate

9-3

CHLORINE.DETERMINATIONS AND THEM DITEFtPRETATIL:.

I INTRODUCTION

.Chlorine normzlly is applied to water as abactericidal agent; it reacts with water con-taminants to form a variety of productscontaining chlorine. The difference betweenapplied and residual chlorine represents thechlorine demand of the water under conditionsspecified. Wastewater chlorination is parti-cularly difficult because the concentration oforganisms and components susceptible tointeraction with chlorine are high and variable.Interferences with the chlorine determinationin wastewater confuse interpretation withrespect to the chlorine residual at a giventime and condition, its bactericidal potency.or iaTuture behavior.

II CHEMISTRY OF CHLORINATION

A Chlorine compounds (C12) dissolve in water.and hydrolyze immediately according to thereaction.

Cl2 H20 __. HOCI + H+ + Cl

The products of this reaction are hypo-chlorous and hydrochloric acid. Thereaction is reversible. but at pH valuesabove 3.0 and concentrations of chlorinebelow 1000 mg/I the shift is predominantlyto the right leading to hypochlorchnt acid.

. (HOCI).

Hypochlorous acid is a weak acid and con-sequently ionizes in water according to theequation:

HOCI H+ + opt:

'This reaction is reversible. At a pH valueof 5.0 or below almost all of the chlorineis present as hypOchlorous acid (HOCI)whereas above pH 10.0 nearly all of it

PC. I Id. 11.77

exists as hypiichlorite ion (0C1-). The pH'value that will control is the pH value

reached after the addition of rhlorine.Chlorine addition tends to Inver the pHand the addition of alkali hypochloritestends to raise the pH.

B The initial reactions on adding chlorine towastewaters may be assumed to be funda-mentally the same as when chlorine is .added to water except for the additionalcomplications due to contaminants andtheir concentration.

Hypochlorous acid (HOCI) reacts withammonia and with many other complex&fricatives of ammonia to produce com-.pounds known as chloramines. Formationof the simple ammonia chloramines includes:

I NH3 + HOCI NH2CI + H2O

monochloramine

2 NH2CI + + H2O

dichloramine

3 NH2CI + NIICI2 N2 + '3 HCI

The distribution of the ammonia chloraminesis dependent on pH, as illustrated below:

Percentage of Chlorine Present asPh

5

7

8

9

Monochloramine Dichloramine

18

38

85

85

94

84

82

35

15

G54

Chlorine Determinations and 'their Interpretation

The formation of the ammonia chloraminesare dependent on pH, temperature, andchlorine-ammonia ratio. Chlorine re-

actions with amino acids are likely;product disinfecting powers are lowerthan those of chlorine or of ammoniachloramines.

RI TERMINOLOGY

A Terms used with Respect to ApplicationSite

I Pre-chlorination - chlorine addedprior to any other treatment.

2 Post-chlorination - chlorine addedafter other treatment.

3 Split chlorination - chlorine added atdifferent points in the plant - mayinclude pre- and post-chlorination.

B Terms Used in Designating ChlorineFractions

1 Free available residual chlorine - theresidual chlorine p-esent as hypo-chlorous acid and hypochlorite ion.

2 Combined available residual chlorine -the residual chlorine present aschloramines and organic chlorine con-taining compounds. ,

.3 Total available residual chlorine - the -

free available residual chlorine + the.combined available residual chlorine -may represent total amount of chlorineresidual present without regard to type.

In ordinary usage .these terms areshortened to free residual chlorine.combined residual chlorine and totalresidual chlorine. In the chlorinationof wastewaters only combined residualchlorine is ordinarily present and isoften improperly termed chlorineresidual.

C Breakpoint chlorination specifically refersto the ammonia-chlorine reaction whereapplied chlorine hydrolyzes and reacts toform chloramines and HCl with the

10-2

chloramines eventually forming + HClas in 11.B.3. Assuming no other chlorinedemand, the total chlorine residual willrise, decrease to zero and rise again withincreasing increments of applied chlorine.Other substances may produce humps inthe applied chlorine vs residual chlorineplot due to elidation of materials otherthan ammonia. Sometimes these areerroneously considered as a b2ealtpoint.

IV IODOMETRIC TITRATION ANALYSES( 2)

lodometric titration using either anamperometric or a starch-iodineend point determilies chlorineresidual.The relative advantages of a specificdetermination depend upon the form in whichthe reactable chlorine exists and the amountand nature of interferences in the water.

A Amperometric Titration - Direct Method

1 Scope and application

This method is applicable to thedetermination of free, combined ortotal residual chlorine in all types ofwater and wastewaters that do notcontain substantial amounts of organicmatter.

2 Summary of Method

ilk

fij

When the cell of the titrator is immersedin a sample at pH 7.0, the cell unit'pro-duces a small direct current if freechlorine (an oxidizing agent) isspresent.As phenylarsirie oxide (PAO) solutionis added, it reduces the free chlorine.When all the chlorine is neutralized, thegeneration of current ceases. At thisend point. the microarrimeter pointer onthe apparatus no longer deflectsdown-scale.

To determine combined chlorine. pH 4. 0buffer and potassium iodide are thenadded to the sample. Free iodinereleased by the combine chlorine alsocauses'the cell to produce a small directcurrent. Addition of PAO reduces thefree'iodine and the generation of currentceases. Again, the end point occurs

Chlorine Determinations and Their Interpretation

when the microammeter pointer nolonger deflects down-scale.

In either titratiorf, the amount of PAOreducing agent used to reach the endpoint is ultimately stoichiometricallyproportional to chlorine present in thesample. The -sum of the free andcombined chlorine is the total residualchlorine in the sample.

Total residual chlorine can be deter-mined directly by 'adding pH 4.0 bufferand potassium iodide to the samplebefore beginning the titration. Anyfree or combined chlorine present willstoichiometrically liberate free iodinewhich is then reduced with PAOtitrarit. The amount of PP.0 titrant,used measures the total amount of freeand combined chlorine originallypresent. in the sample.

3 Interferences

a Organic matter reacts with liberatediodine.

b Cupric ions may cause erraticbehavior of the apparatus.

c Cuprous and silver 'ions tend topoison the electrode by plating outon it.

'Amperometric Titration- Indirect Method

I Scope and Application

This method is applicable to thedetermination of total chlorine residualin all. types of water End wastewaters.In contrast to the direct amperometrictitration, this back-titration procedureminimizes interferences in waterscontaining substantial amounts oforganic matter.

2 Summary of Method

A sample is treated with a measuredexcess of standard phenylarsine oxide(PAO) solution followed by additionof potassium iodide and a buffer tomaintain the pH between 3.5 and 4.2.

Any form of chlorine present willstoichiometrically liberate iodinewhich immediately reacts with thePAO before significant amounts arelost to reactions with organic matterin the Sample.

When the cell of the amperometrictitrator is immersed in a sample sotreated, no current is generated sinceneither free chlorine nor free iodineis present.

..The amount of PAO used to reduce theliberated iodine is then determined by

. titrating the excess with a standardiodine solution. No current 'is generateduntil all the excess PAO has beenoxidized by the iodine. At this endpoint the next small addition of iodinecauses current to be generated and themicroammeter pointer. permanentlydeflects up-scale.

The excess PAO thus measured is.subtracted from the original amountof PAO added. The difference is thePAO used to reduce the liberated iodineand is ultimately a measure of the total

,chlorine originally present in the sample.

NOTE; Sodium thiosulfate solution maybe used instead of PAO, but PAO ismore stable and 'is to be preferred.

3 Interferences

a Cupric ions may cause erraticbehavior of tl)e apparatus.

b Cuprous and silver ions tend topoison the electrode by plating outon it.

'C Colorimetric Starch-Iodide Titration -Indirect Method

67

I Scope and Application

This method is applicable to thedetermination of total chlorine residualIn all types of water and wastewater.A back-titration procedure is used tominimize interferences in waters con-taining eubstanal amounts of organicmatter.

I0-3

Chlorine Determinations and Their Interpeetatio n

2 Sumtnary of Method

A sample is treated with a measuredexcess of standard phenylarsine oxide(PAO) solution followed by additionof pdtassium iodide and a buffer tomaintain the pH between 3.5 and 4, 2,>'Any form of chlorine present willstoichiometrically liberate iodinewhich immediately reacts with PAObefore significant amounts are lost h.reactions with organic matter in thesample.

The amount of PAO csedto reduce thelilaerated iodine is then determined bytitrating the ogress with a standiodine solution in the pr chuntil the PAD is completely oxiAt this end point, the next small additioinof iodine causes a faint blue color to Vpersist in the sample.

The excess PAO thus measured issubtracted from the original amountof PAO added. The difference is thePAO used to reduce the liberatediodine and is ultimately a measure of.the total chlorine originaily presentin the sample.

D Evaluation of lodometric Analyses

!odometric titration using amparometricend point detection' appears to be the moreaccurate residual chlorine method -Besides being inherently, m,.re accurate thancolor.detection methods, this electrical endpoint is free of interference from color_and turbidity.

. -.

The accuracy of the colorimetric starch-iodide end point is improved by employingthe indirect titration method described,abOve. By aNdding an excess of the standardreducing agent and book-titrating. contactbetween the liberated iodine and organicmatter in the sample is minimized.

NOTE: Sodium thiosulfate solution maybe used instead of PAD, but PAD ismore stable and is to be preferred. ;

3 Interferences,

10-4

a An unusually high content of organicmattermay cause some uncertaintyin the end point. If manganese.iron and nitrite are definitely absent.this uncertainty can be reduced byacidification to pH 1,0,

b Color and turbidity.in the samplecause difficulty with end-pOintdetection.

I

A

DPD METHODOLOGY (1)

The DPD (N. N-diethyl-p-phenylenediamine)method can be applied by either titration orspectrophotornetry.

Titration

In this procedure, the buffered sampleAstitrated with termite ammonium sulfate tothe disappearance of the red color; theresult is free available chlorine. Using thesame sample. the titration can be,darriedfurther to determine mono-and dichloramine.:fitrogen trichloride is found, using a freshportion of sample.

B Spectrophotometry

Alternatively, the red colors in A canread in in a spectrophotometer or filter photo-meter at 515 nm, Th concentrations aredetermined using a ibration graph.

6 c"

ry

VI COMPLP NNCF: NIETRODOLOGY

A NPUES/Certifieations

All of the analytical procedures,described in IV. :Jdometric TitrationAnalyses knd in V.. DPD Methodology(abovel are cited in the FederalRegister as approve-4.

II Drinking Water

Only thq DPD Methodology (as in V. above) is cited in the Federal Register

as approved. In contrast to the NPDES/Certifications regulations, the DPDtrrit kit is alas appro..1,1 for drinking Water.

ACKNOWLEDGEMENT:

Significant portions of this outline werewritten by J. L, Holdaway, Chemist.Technical Program, USEPA. Region ill.Charlottesville. VA 22001 (1971) and by ,

Charles R. Feldmann, Chemist, NationalTraining and Operational Technology .

('enter. MOTD, OWPO, USEPA,Cinrinnati, Ohio'45268,

Chlorine Determination arid Their Interpretation

It EFERENCES

1 Standard Methods for the Examination ofWater oral WasteWaters. 14th Ed..APHA. AWWA. WPCF. 1976.

2 Book of ASTM Standards, Part 31.Wate. American Societyfor 'testing and Materials.Philadelpnia. PA. 1975.

3 Sawyer. C. N. CLernistry for SanitaryEngineers. McGraw-Hill BookCompany. New York. 1960.

4 Moore, E.W. Fundamentals ofChlorination of Sewage and Wastes.Water and Sewage Works. vol. 9,,No. 3. March 1951,

5' Day. R. V., Horchler, D. II.. andMarks, It. C. Residual ChlorineMethods and Disinfection of Sewage.Industrial and Engineeri.g Chemistry.May 1953.

6 Marks, H. C., Joiner, R. R., andStrandskov, F. B. AmperometricTitration of Residual Chlorine inSewage. Water and Sewage Works.May 1948.

This outline was updated by Audrey D. Kroner,Chemist, National Training and OperationalTechnology Centlr, MOTD, OWPO,' USEPA,Cincinnati, Ohio 45268

. Descriptors: Chemical Analysis, Chlorination.Chlorine. Disinfection. Sewage Treatment.Wastewater Treatment. Water Analysis.

10-5

PHOSPHORUS IN THE AQUEOUS ENVIRONMENT

i PhOsphorus is dos,'" associated withwater quality because o: a) its role inaquatic productivity such as algal blooms,(b) its sequestering .ictlon. which causesinterference in coagulation. (c) the difficultyof removing phdsphoris from water to somedesirable low concentration, and (d) itsch.lracteristic of converting from one toanother of many possible forms.

A Phosphorus 1i one of the primary nutrientssuch as hydrogen (H), carbon (C),nitrogen (N), sulfur (S) and phosphorus (P).

Phosphorus is unique among nutrientsin that oxidation sloes not contributesignificant energy because it commonlyexists in oxidiz. ' form.

2 Phosphorus is intir ,tely involved inoxidative energy release from am-vnthesis of other tiutrieits into tellmass via:

a Transport if nutrients ac-ossmembranes into cell islikely to includ. phost1 irylati n.

The release eqergy for meta-bolic purposes is lii.elyincludd a triphorthate exchangemechanism.

b

B Most natural waters contain relatively low:evela of P (0.01 to 0.05 mg/1) in theaoluble state during pet lode of significant'productivity.

I Metabolic activity tends to conv.rtsoluble P into cell mass (organic P) asa part of the protoplasm, intermediateproducts, or sorbed material.

2 Degradation of cell mass and incidentalP compounds results in a feedback oflysed P to the water at rates governedby the type of P and the environment.Aquatic metabolic kinetics show markedinfluences of this feedback.

CH. PHOS. 4e. 11.77

3 The concentrations of P in hydrosolls,sludges, treatment plant samples andsoils may range from 102 to i06 timesthat in stabilized surface water. Bothconcentration and interfering cor.ipo-nents affect applicability of analyticaltechniques.

The primary source of phosphoz.us in theaqueous system is of geological origin.Indirect sources are the processed mine mlproducts for use in agriculture, household,industry or other activities.

A Agricultural fertilizer run-of: is relatedto chemicals applied, farming practiceand soil exchange capacf.y.

B Wastewaters primarily of domesticorigin contain major amounts of P from:

1 Hurnan,animal anti plant residues

2 Surfactants (craning agei..) discharge

7 Microbial and other cell masses

C Wastewaters primarily of Industrialorigin contain P related to:

I Corrosion control

2 Scale control additives.

3 Surfact ,,its or dispersants

4 'Chemical trocessing of materialsincluding P

5 Liquors from clean-p operations ofdusts, fumes, stack gases, or otherdischarges

III Phosrhorus terminoloey is commonlyconfused because of the h.ierreit.tions amongbiological, chemical, engineering, physical,and analytical factors.

70

Phosphorus in the Aqueous Environment

A Biologically, phosphorus may be availableas a nutrient, synthesized into living mass,stored in living or dead cells, agglomerates,or mineral complexes, or converted todegraded materials.

B Chemically, P exists in several mineraland organic forms that may be convertedfrom one to another under favorableconditions. Analytical estimates arebased upon physical :.r chemical techniquesnecessary to convert various forms of Pinto ortho phosphates which lone can bequantitated in terms of the molybdenumblue colorimetric test.

C Engineering interest in phosphorus isrelated to the prediction, treatment, or

.control of aqueous systems to favoracceptable water quality objectives.Phosphorus removal is associated withsolids removal.

D Solubility and temperature are majorphysical factors in phosphorus behavior.Sq1uPle P is much more available thaninsoluble P for chemical or biologicaltransformations and the rate of conversionfrom one to another is strongly influencedby temperature.

E Table 1 includes a classification of thefour main types of chemical P and someof the relationships controlling solubilityof each group. It is apparent that noclea: -cut separation can be made on asolubility basis as molecular weight,substituent and other factors affectsolubility.

F Table 2 inch.des a scheme of analytical!ifferentiation of various forms of P

based upon:

1 The technique required to convert anunknown variety of phosphorus intoortho P which is the only one quanti-tated by the colorimetric test.

11-2

2 Solubility chP or moreto clarify t

acteristics of the sampleecisely the means requiredsample.

a Any c rification method io subjectto in mplete separation. Therefore,it is ssential to bpecify the methodused to interpret the yield factor ofthe paration technique. Thedegr e of separation of soiublesand solubles will be significantlydifferent for:

1 Membran. filter separation(0.5 micron pore size)

2 Centrifugation (at some specifiedrpm and time)

3 Paper filtration (specify paperidentification)

4 Subsidence (specify time andconditions?

G Analytical separations (Table 2) like thosein Table 1, do not give a precise separa-tion of the various forms of P which maybe included quantitatively with ortho orpoly P. Conversely some of the poly andorganic P will be included with ortho P ifthey have been partially hydrolyzedduring storage or analysis. Insolublesmay likewise be included as a result ofpoor separation and analytical conditions.

1 The separation methods provide anoperational type of definition adequateit most situations if the "operation"16 known. Table 2 indicates the natureof incidental P that may appear alongwith the type sought.

Ii

Phosphorus in the Aqueous Environmiut

Table .1

PHOSPHORUS COMPOUNDS CLASSIFIED BYCHEMICAL AND SOLUBILITY RELATIONS .

Form Water Soluble") Insoluble(1)

1. Ortho phosphates Combined with monbvalent Combined with multications such as H;Na71011H44. valent cations such

(PO4)-3as Ca +2A1 +3Fe +3

2. Poly phosphates

(P20

7).

-4(P30

10)-5

(1.30

9)-3

and others depending uponthe degree of dehydration.

as in 1 aboveIncreasing dehydrationdecreases solubility

(a) as in 1 above(b) multi P polyphosphates

(high mol. wt.1 in-cluding the "glassy"phosphates

3. Organic phosphorus (a) certt.in chemicals (a) certain chemicalsR-P, R-P-R (2) (b) degradation products (b) cell mass, may be(unusually varied nature) (c) enzyme P colloidal or agglom-

(d) phosphorylated nutrients erated(c) soluble P sorbed by

insoluble residues "'4. Mineral phosphorus (alas in 1 above (a) as in 1 above

(b) as in 2 above(c) geological P such as

phosphosilicates(d) certain mineral com-

plexes.

(1) Used in reference to predominance under common conditions.-3

(2) R represents an organic radical. P represents P, PO4, or its derivatives.

2 Total P in Table 2 includes liquid andseparated residue P that may exist inthe whole sample including nth, organicsludge, or hydrosoils. This recognizes

that the feedback of soluble.P fromdeposited or suspended material has areal effect upon the kinetics of theaqueous en- ,ronment.

72 11-3


Table 2

PHOSPHORUS COMPOUNDS CLASSIFIED BYANALYTICAL METHODOLOGY

Desired P Components Technique (1) Incidental P Included (2)

1. Ortho phosphates No treatment on clearsamples

Easily hydrolyzed(a) poly phosphates -(1t) organic -P, -(c) Mineral -P, + or -

2. Polyphosphates(2)-(1) Poly P(hydrolyzable)

acid hydrolysis onsclearsamples, dilute

(a) F1 2SO4

(b) HC1heated

(a) ortho-P +(b) organic -P + or -(c) mineral -P + or -

3. Organic phosphorus(3) - (2) + org P(hydrolyzable)

4. Soluble phosphorus(preferably classifiedby clarification method)

5. Insoluble phosphorus(residue from clari-fication)

acid + oxidizing hydrolysison whole sample. dilute

(a) H2SO4 + HNO

3(b) H

2SO4 + (NH

4)2S208

heated

(a) ortho P +(b) poly P +(c) mineral P + or

clarified liquid followingfiltration, centrifugatloor subsidence

generally includes(a) 1, 2, or 3(b) particulates not

completely Separated

Retained residne eparated's (a) generally includesduring clarification sorbed or complexed

See (8)

8. Total phosphorus Strong acid + oxidantdigestion

(a) H2SO4 + HNO3

(b) H2SO4 + HNO3 + HC1O4

(c) F1202 + Mg(NO3)2 fusion

all components in1, 2; 3, 4, 5 in thewhole sample

(1) Determinative step by ph.. p`l molybdate colorimetric method.a

(2) Coding: + quantitative yiel- a small fraction of the amount present+ or - depends upon the individual chemical and sample history

11-4

73


IV Polyphosphates are of major interest incleaning agent formulation, ac, dispersants,and for corrosion control.

A They are prepared by dehydration of orthophosphates to form products having two ormore phosphate derivatives per molecule.

1 The simplest polyphosphate may beprepared as follows:NaO Nag,

HO --P 0 het HOOP 0--.2

0 O

HO \P 0Ns° HOT

NaO

mono sodium orthophosphate (2)

+ H2O

disodium dihydrogenpolyphosphate

2 The general form for producingpolyphosphates from mono substitutedorthophosphates is:

n (NaH PO) heat(NaP03)n+ n H20a2 4 200-4o

3 Di-substituted ortho phosphates ormixtures of substituted ortho phosphateslead to other polyphosphates:

1leselP0.Medium hydros*.

oath., phosphate

Na112104 laa4 StaP100 21120

mono .Ovum ponnatodnen motorel hydrogen talphoephste

oath, phosphate

4 The polyphosphate Relief; usuallyconsist of the polyphosphate anionwith a iirgutive c.iairge of 2 to 5.Hydrogen ormoteis commonly occupythese mites. Thz Polyphosphate Lan befurther dehYdra:cd by heat an Intl ashydrogen I./stains. Dior ttivalentcations generally produce a more

insoluble polyphosphate than the samecation in the form of insoluble orthophosphate. Insolubility increases withthe number of P atoms in the

,polyphosphate. The "glassy" poly-phosphates are E. special gees,' withlimited solubility that r re used to aidcorrosion resistance in pipedistribu-tion systems and similar ries.

B Polyphosphates tend to hydrolyze or"revert" to the ortho P form by additionof water. This occurs wheneverpolyphosphates are found in the aqueousenvironment.

.

1 The major factors affecting the rate ofreversion of poly to orthophosphatesinclude:

a) Temperature, incr sed T increasesrate

b) pH, low:: s rate

c) Enzyme,.,increar,.. P:1 to

zymes

d) Coll, terease rate

e) Conn...ex:rig -s and ionicconc:P.: rioi ea . :ease rate

f) of the ,polyphosphateincre: ..:ate

2 Items a, b eot c have a large effezupon reversion rate compared withother factors listed. The actualreversion rate is a combination oflisted items and other conditions orcharacteristics.

3 The-difierences among ortho a id ortho4- polyphosphates commonly are close to'experimental error of the colorimetrictest to stabilized surface, water samples.A significant difference generallyindicates that the sample was obtainedrelatively close to a sou..ce of poly-phosphates and was promptly artalyzed.Th:s implies that the re' ersion rate ofpolyphosphates is much . igher thangenerally believed.

5


V SAMPLING AND PRESERVATIONTECHNIQUES

A Sampling

1 Great care should be exercised toexclude any benthic deposits fromwater samples.

2 Glass containers should be acid rinsedbefore use.

3 Certain plastic containers may beused. Possible adsorption of low con-centrations of phosphorus should bechecked.

4 If a differentiatim: of phosphorus formsis to be made, filtratlea should becarried out immediately upon samplecollect:on. A membrane filter of0.45e1 pore size is recommended forreproducible separations.

Preservation

1 If at 471 possible, samples should beanalyzed on the day of collection. Atbest, preservation measure v onlyretard possible changes in the sample.

Possible physical changes includesolubilizastion, precipittlion,absorption on or desorption fromsuspended matter.

b Possible chemical changes includereversion of poll to ortho P anddecomposition organic or min- .

era' P.

c Possible biological changesinclude mien:Mal decompositionof organic P and algal orbacteria: growth forming organic P..

S it is impoesible to do total phos-phorus determinations on the day ofcollection, refrigerate at 4C andadd 2 ml concesstrated 113804 or40 mg !e4C12/11ter. Limit of holdingfor samples thus preserved is 7 days.

11-8

3

a Refrigera.:en decreases hydrolysisand reectr It rates and also loose°due to .)1r.tility.

b Sulfuric acid limits biologicalchanger.

c Mercu.:a chloride also limitsbioloqic.e; changes. bet interfereswith the res:calytical procedure ifthe chloride level is lee:: eh::: 50 mgCI /'liter, (See VI H. 2. belo).Diescoas% of mercury-containingtee. weocs also ackie time o the

.447/11re,

Consult the P.PA Mmec:a Manual(6)for pmeeret' sv me ,.,sures applicableto ecry.ex ca determinevarious iractter iltosphorue.

VI THE EPA ANALYTICAL PROCEDURE(6)

A This is a cede: imetric determination,specific for orilmhosphate. Dependingut the ruceoro of :he sample and on thetype a OM ZJught, the procedure in-owe, ..es,- general operations:

1 C:,M,ersior, of phosphorus forma tof -tuble orthophosphate (See Fig. 1):

a sulfuric acid-hydrolysis forpolyphosphates, and someorganic P compounds,

b persulfate digestion for organicP compounds.

2 The color determination: involvesreciting dilute solutions of phosphorus

ammonium molybdate andpotassium antimonyl tartrate in anacid medium to form an antimony-phosphomolybdate complex. Thiscomplex is reduced to an intenselyblue-colored complex by ascorbicacid. The color is proportional tothe orthophosphate concentration.

Color absorbance is measured at880 nom or 850r= ands concentrationvalue obtainedv sing a. standard curve.

Reagent preparation and the detailedprocedure can be found in the EPAmanual.

The methods described there areusable in the 0:01 to 0.5 mg/literphosphorus range. This range canbe extended by dilution of samples.


ri Pomo IrateDimestion

'Total

Colo rime ry

) OrthephooplZ7

Filter 0.45 micrometer Membrane Filter

Direct 113004 Penni:auColorised ry Hydrolysis 4

Co lariartryDigestion 40,1orinetry

inorgdnicphosphoruscompound.

A Interferences

LSoluble HydrolysableiOrthophosphate

polyphosphatecome organic

phosphoruscompounds

FIGURE IANALYTICAL SCHEME FOR DIFFERENTIATION OF PHOSPHORUS FORMS

4 The total phosphorus procedure requiresa pH.adjustment with a pH meter. Buffersmade with phosphates are used to calibratethe meter in the applicable range. Themeter electrodes must be thoroughly flushedfree of buffer before their use with phr- -phorus test solutions. Otherwise, significantphosphorus contamination will result.

.

mordoxidisable organicphosphoruscompounds

Erroneous results from conlAminatedglassware is avoided by cleaning itwith hot 1:1 MCI, treating it withprocedure reagents and rinsings withdistilled water. Preferably thisglassware shOuld be used only for thedetermination of phosphorus and pro-tected from dust during storage.Commercial detergents should neverbe used.

2 If HgC12 is used as a preservative.it interferes if the chloride level ofthe sample is less than 50 mg Cl/liter.Spiking with NaC1 is then recommended.

3 Low total phosphomili values have beenreported because of possible adsorptionof phosphorus on iron, aluminum, man-ganese or other metal precipitatesformed in wastewater samples.

a Filter such samples after digestionand redissolve the metal hydroxidesthat form with 2-3 drops of to 11 Nsulfuric acid used in the hydrolysisstep.

b Filter through phosohorue-free0.45 micrometer pore size cellulosefllters. See Standard Methods, (7)page 472 about washing, filters beforeuse, since the discs can introducesignificant phosphorus contamination.

5 Others have reported interference fromarsenic, arsenates, chlorine, chromium,sulfides. nitrite. tannins, lignin and otherminerals and organics at high concentrations.

C Precision and Accuracy(6)

I Organic phosphate - 33 analysts in19 laboratories analyzed naturalwater samples containing exact in-crements of organic phosphate of0.110, 0.132, 0.772, and 0.882 mgPatter.

Standard deviations obtained were0.033, 0.051, 0.130 and 0.128respectively.

Accuracy results as bias, mg P/liter'were: + 0. 003, + 0. 018, + 0.023 and- 0.008, respectively.

2 Orthophosphate was determined by28 analysts in 18 laboratories usingsamples containing orthophosphatein amounts of 0.029, 0.038, 0.335and 0.383 mg P/liter.

Standard deviations obtained were010, 0.008, 0.018 and 0.023 respectively./

11-7


Accuracy results as bias, mg Miterwere -0.001, -0.002, -0.00E0 and-0.007 respectively.

D Automated Methods

The E'PA Nlantrtl also contains a procedurefor the automated colorimetry method usingascorbic acid as the reducing agent.

VII VARIABLES IN THE COLORIMETRICPROCEDURE'

Several important variables affectformation of the yellow heteropolyacid and its reduced form, molybdenumblue, in the colorimetric test for P.

A Acid Concentration during color develop-ment LB critical. Figure 2 showthatcolor will appear in a simple containingno phosphate if the acid concentrationis low. Interfering color Ls negligiblewhen the 'norrnalfirwith respect toH

2SO4 approaches 0.4. -

1 Acid normality during color develop-ment of 0.3 to slightly more than0.4 Ls feasible for use. It is prefer-able to control acidity carefully andto seek a normality closer to thehigher limits of the acceptable range.

2 It Ls essential to add the acid andmolybdate as one solution.

3 The aliquot of sample must beneutralized prior to adding thecolor reagent.

11 -8

Figure 20-PHOSPHATE COLOR

VS ACIDITY

11 Choice of Reductant - Reagent stability,effective reduction and freedom fromdeleterious side effects are the basesfor reductant selection. Sepral re-ductanta have been used effectively.Ascorbic acid reduction is highlyeffective in both marine and fresh water.It is the reluctant specified in themanual NPDES procedure.

C Temperature affects the rate of colorformation. Blank, standards, andsamples must be adjusted to the sametemperature (I" 1°C), (preferably roomtemperature), before addition of theacid molybdate reagent.

D Time for Color Development must bespecified and consistent. After addition,of reductant, the blue color developsrapidly for 10 minutes then fades grad-ually after 12 minutes.


VIII DETERMINATION OF TOTAL ,

PHOSPHORUS

At Determination of total phosphoruscontent involves omission of anyfiltration procedure. It utilizes the acid-hydrolysis and persulfate treatments

. to convert all phosphorus forms to thetest-sensitive orthophosphate form.

B Determining total phosphorus contentyields the 1...ost meaningful data sincethe various forms of phosphorus maychange from one form to arother in ashort period of time. (See part V, BO

. DC DEVELOPMENT OF A STANDARDPROCEDURE

Phosphorus analysis received intensiveinvestigation; coordination and validation ofmethods is more difficult than changingtechnique.

A Part of the problem in methods arosebecause of changes in analytical objectivessuch as:

1 ,Methods suitable to gather "survey"information may not be adequate for"standards".

2 Methods acceptable for water are notnecessarily effective in the presenceof significant mineral and organicinterference characteristic of hydro-soils, marine samples, organicsludges and benthic deposits.

3 Interest has been centered on "fresh"water. It was essential to extend themfor marine waters.

9

4 Instrumentation anda.utomatton haverequired adaptation if methodology.

B Analysts have tended to work on t....1r own ,specialsroblems. If the methodapparently served their situations, it wasused. Each has a "favorite" scheme thatmay be quite effective but progresstoward widespread application of "one"method )as been slow. Consequently,many methods are available. Reagent'acidity, Mo content, reductam andseparation techniques are the majorvariables.

C The persulfate digestion and single reagent(ascorbic acid) method described in VIabove is the only method currentlylisted In the Federal Register "List ofApproved Procedures" for NPDESre-ruirements.

ACKNOWLEDGMENT:

Materials In this outline include significantportions of previous outlines by J. M. Cohen,L. J. Kamphake, and R. J. Lishka. Importantcontributions and assistance were made byR. C. Kroner, E. F. Barth, W. Allen Moore;Lloyd Kahn, Clifford Risley, Lee Scarce,John Winter, and Charles Feldmann.

REFERENCES

1 Jenkins, David, A Study of MethodsSuitable for the Analysis andPreservation of Phosphorus Formsin the Estuarine Environment. DHEWCentral Pacific River Basins Project.SERL Report No. 85-18, Universityof California, Berkeley, Calif.November 1985.

11-9


2 Gales, Morris E. , Jr.. Julian, Elmo C. ,and Kroner, Robert C., Method forQuantitative Determination of TotalPhosphorus in Water. SAWWA 58:(10) 1363. October 1966.

J Lee, G. Fred, Clesceri, Nicholas L. andFitzgerald, George p., Studies on theAn'alysis of Phosphates in Algal Cultures.Int. .1. Air & Water Poll. 9:715. 1965.

4 Barth, E. F. and Salotto, V. V.,Procedure for Total Phosphorusin Sewage and Sludge, UnpublishedMemo, Cincinnati Water ResearchLaboratory, FWQA. April 1966.

5 Moss, H: V. , (Chairman, AASGPCommittee) Determination of OrthoPhosphate, Hydrolyzable Phosphateand Total Phosphate in Surface Water,JAWWA 56:1563. December 1.958.

6 Methods for Chemical Analysts or ',Velar& Wastes. EPA, MDQARL. Cincinnati,Ohio 45268. 1174.

7 Standard Methods for theExamination of Waterand Wastewater. 14th ed..APHA-AWWA-WPCF.Washington. D. C.. 1976.

11-10

This outline was prepared by Ferdinand .1.Ludzack, former Chemist. National TrainingCenter. and by Audrey D. Kroner. Chemist.National Training and Operational TechnologyCenter. MOTD, OWPO. USEPA, Cincinnati.Ohio 45288. . I

Descriptors: Chenalcal Analysis. Nutrients.Phosphates. Phosphorus. Phosphorus Compounds.Pollutant Identification. Sampling. WaterAnalysis. Water Pglution

79

CONTROL OF INTERFERING IONS IN FLUORIDE DETERMINATIONS

The principal source of error in fluorPreanalysis is the presence of interfering ions.This is particularly true in the colorimetricmethods, as can be seen from Table I whichlists some tons commonly. found in water andtheir affect on the Standard Methods fluorideanalyses.

A In colorimetric analysis, one of themechanisms by which these ions causeerror is the changing of the reaction rate.Since the determination is based on colordevelopment, variations in reaction rate

cause variations in fluoride reading.

Some ions complex with either fluoride,in all methods, or with zirconium, in thecolorimetric methods. When fluoride iscomplexed, low results are obtained,and when zirconium is complexed, theintensity of color is altered.

C Chlorine bleaches out the colors of, dyes,and must always be removed before the

. sample can be analyzed colorimetrically.

II Whenevir the quantity of interfering ionsin .the water is sufficient to cause an error of .0.1 ppm fluoride or more, or whenever theanalysis is unknown, these interferences mustbe removed or their effects diminished by oneof the following methods:

A If the interferences are known to be causedby chemicals added,during treatment in thewater plant, they may sometimes be avoidedby appropriate selection of a samplingpoint within the plant.

B In some cases the water sample can bediluted to bring the level of an interferingion below the critical point. This procedureis applicable only when the fluoride level issufficiently high to permit accurate 'analysison the diluted sample.

C When the identity of the interfering ion isknoim, it may be possible to select ananalytical method which has adequatetolerance for that ion.

TABLE I. INTERFERENCESConcentration of Substance, in Mg /L, Required to

Cause an Error of Plus or Minus 0.1 Mg /L at1.0 mg/t, F.

AlkalinityAluminumChlorideIronHexametaphosphatePhosphate

Chlorine

Color & Turbidity

SPADNS

5,000 (-)(-).

7,000 (+)10 (-)

1.0'(+)16 (+)

Electrode .

7,060 (+13.0 (-)

20,000 (-'200 (-)

>50, 000

>50,00050,000 (-)

1i u @1 I. r mpletely'Removed W .th A rsenite > 5,000

Moselle Removed orCompensated For,

Above Figure is for Immediate Reading. Allowed to Stand Two HoursTolerance is 3.0 mg/L. Four Hour Tolerance is 30 Mg /L.

CH. HAL. f. 34b. 11.77

8012-1

Control of Interfering Ions

D When the composition of the unfluoridatedwater is known and constant, equivalentquantities of interfering ions can be addedto the fluoride standards, thereby neutral-izing the effect of those tons,

E In all other cities the water sample mustbe distilled, As can be stele from Table I,distillation will seldom be necessary whenthe electrode method is used.

III The principle of the diktillation processis the conversion of fluoride to the volatile .'acid, II2SiF6, in the presence of sulfuricacid and silica (glass beads). The fluasilicie.acid distills over, leaving most of the inter,fering ions behind.

A The apparatus used is illustrated inFigure 1, It consists of a distillationflask, connecting tube and condenser. Forconvenience, apparatus with ground-glassjoints is used, but a simpler arrangementusing rubber stoppers, is satisfactory(Figure 2),

B The critical features of the apparatus arethe diameter of the connecting tube, theimmersion of the thermometer, and fit ofstoppers and/or ground -glass joints.,

'1 The diameter of the connecting tubemust be large enough to preclude .?.ecarryover of Nibbles,

2 The thermometer must be positioned lowenough so that it will always be immersed,

3 Stoppers and joints must be tight enoughto prevent the loss of fluoride-containing'vapor,

C The Distillation Procedure is CarriedOut as Followsi

I Prepare the still by placing 400 ml dis-tilled water, some glass beads and then200 rr.1 cancentrated acid in the flask,Add the acid slowly and Stir thoroughly.After all the acid has been added, stir '

again until the mixture is homogeneous.

2 Connect the apparatus as shown in thedrawing, start water thrcugh the con-denser and begin heating slowly, If

bumping occurs, the acidand water havenot been mixed sufficiently. Whenboiling 'Mirth, heating inaybe increased.

12-2

3 Continue heating until the temperaturereaches 180°C, Discard this distillate, fsince it contains traced of fluoride pornthe acid and glassware.' This prelim-inary procedure also serves to adjust the.acid-water ratio for subsequent distillations,

4 Allow the flask to cool um ilthe temper-ature drops to 120 C or lower, Measureout a 300-m1 sample and add it t, theflask,' Mix thoroughly,

5 Distill as before until the temperaturereaches 180°C, Retain the distillate(there should be 300 ml) for colorimetricdeterminations,

D The distillation process must be carriedout very carefully, since there areseveral possible sources of difficulty.

1 The flame under the distillation flaskmust never touch the sides of the flaskabove the liquid level. Superheatingof the vapor results in high sulfate

. car'ryover which causes a sulfate inter-ference,

2 All stopper and joints must fit tightlyto. prevent loss of fluoride,

3 Flask contents must be thor:oughlymixed to prevent bumping.

4 Distillation must be stopped when the .temperature reaches 180°C, Highertemperatures result in :Accessivesulfate carryover.

5 Silver sulfate, at the ratio of 5 mg/mgof Cl, should be added when high-chloridesamples are distilled, The presence ofsilver inhibits the of HClwhich, in sufficient quantity, could.interfere with the fluoride determination,

6 When high-fluoride samples are distilled,repeat the distillation using 300 ml ofdistilled water, Analysis of the distillatewill indicate hum complete the fluoriderecovery was, If auhatantial amountsof fluoride appear in the second diaSillete;add the quantity to that obtained initiallyand flush again, Quantities of less Wan .

0,1 ppm F (0,03 mg) may be disregarded,

7 Because of the simplicity of apparatus'andprocedure, the distillation procedure canbe readily automated. Modifications in-clude magnetic stirring and a thermostatwhich turns bff a quartz heating mantle,when the correct temperature has beenreached,

Si


Fig. 1 DISTILLATICiNAPPARATUS

TAM.. .hr

C17,,, C/14, Weh.; Mr, I. O.

r 24/40 .Joints

Rubber Veers 0 Adorn",

P4/40 filtt

Coodavair

1000141. Boiling, Flock

, .

300 ml. Volumetric Flock


Fig. 2 SIMPLIFIED DISTILLATION APPARATUS

r o' ,;

(

FI.S..,;", r,

22-4

CON, rube

I

inh:. I. 9.

300 M.. Mork .4.,

8 3

Condenser

300 PL. ErlenrayerFlask

e


IV COMPLIANCE METIIODOLOGY

A NPDES/ Ce rtifications

Manual distillation is not required ifcomparability data on representativeeffluent samples are on company fileto show that this preliminary distilla-tion step is not necessary. However.manual distillation will be requiredto resolve any controversies.

Either an ion elertode or the SPADNSthod ma. M used for the fluoride

doer '1`,.t automated comple,..,,i,t-siirthod is ,ls.....proved.

rincising

reiiminary uistilhtion is required ifiIr SPADNS method is used. It isrequired if th. 'on electrode is used.

EFERENCFS

1 Standard Methods for the Examination ofWater and Wastewater, 14th Edition.p.389. 1978.

2 Bellack. E. Simplified Fluoride DistillationMethod. JAWWA 50:530. 1958.

This outline was prepared by Dr. E. Bellack,Office of Water Supply, EPA. Washington, D.C.

Descriptors, Analysis, Chemical Analysis.Fluoridation, Fluorides. Fluorine. WaterAnalysis.

84 12-5

AMMONIA, NITRITES AND NITRATES

I SOURCES AND SIGNIFICANCE OFAMNIONLA. NITRITES AND NITRATESIN WATER

The natural occurrence of nitrogen com-pounds is best demonstrated by the nitrogencycle (Figure I).

A Ammonia

1 Occurrence

Ammonia is a product of the micro-biological decay of animal and plantprotein. In turn, it can be useddirectly to produce plant protein.Many fertilizers contain ammonia.

2 Significance

The presence of ammonia nitrogenin raw surface waters might indicate

domestic pollution. Its presence inwaters aced for drinking purposesmay require the addition of largeamounts o f chlorine n order t oproduce a free chlorine residual.The chlorine will first react withammmia to form chloraminea be-fore it -vertu its full bactericidaleffects (free chlorine residual).

B Nitrites

Occurrence

Nitrite nitrogen oc Cu r a in wateras an intermediate stage in thebiological decomposition of organicnitrogen. Nitrite formers (nitro-somonas) convert ammonia underaerobic conditions to nitrites. Thebacterial reduction of nitrates canalso produce nitrites under anaero-bic conditions. Nitrite is used asa corrosion inhibitor in industitilprocess water.

2 Significance

Nitrites are usually not found insurface water to a great extent.

CH. N. 6g. 11.77 8,5

The presence of large quantitiesindicates a source of wastewaterpollution.

C. Nitrates

1 Occurrence

air

Nitrate formers convert nitritesunder aerobic conditions to nitrates(nitrobacter). During electricalstorms, large amounts of nitrogen(N2) are oxidized to form nitrates.Finally, nitrates can be found infertilizers.

2 Significance

Nitrates in water usually indicatethe final stages of biological sta-bilization. Nitrate rich effluentsdischarging into receiving waterscan, under proper enaironmemalconditions. cause stress to stream.quality by producing algal blooms.Drinking water containing exces-sive amounts of nitrate's can causeinfant methemoglobinemia.

II PRESERVATION OF AMMONIA. NITRATEAND N;TRITE SAMPLES(8'

A If the sample (a to be analyzed for Ammonia.Nitrate or Nitrite, cool to 4°C and analyzewitnin 24 hours.

B For Ammonia and Nitrate, the storage timecan be ext,nded by lowering tne sample pH toless than 2 by the addition of concentratedsulfur( cid and storing at 4°C. (2 ml of acidper lite a usually sufficient. Check withpll pa r).

C Mercuric cnloride is effective as a preservative.but its use is discouraged because:

1 The Hg ion interferes with some of thenitrogen tests,

2 The Hg presents a disposal problem.

D Even wnen "preserved", conversion from onenitrogen form to another may occur. Samplesshould,be analyzed as soon as possible.

13-1

Ammonia. Nitrites and Nitrates

THE NITROGEN CYCLE

Figure 1

13 -2

Ill DETERMINATION OF A, MONIA

A Nesslerization

1 Reaction

Nessler's r agent, a strona kaline soluZionof potassimercuric iodide, co mbwith NH3 in alkaline s liont o form a yellowish owncolloidal dispersion.

2K2lig14 4 NH3 3K0

Hg./0 + 7K1 + 21120

..NH2

Yellow-Bro m

The intensity of the colorfollows the Beer -Lambert Li vand exhibits maximum absorp-tion at 925 nm.

2 Interferences

a Nessler's reagent formsa precipitate withions (e.g., Ca++ Ye7+,Fe+++, and S'). heseions can be ellmio a* ed in apretreatment floe,nastep with zinc sulfate andalkali. Also. EDTA orRochelle salt solution pre-vents precipitation w it hCa++ or Me+.

b Residual chlorine indicatesammonia maybe presentin the form of chlorarsines.The addition of sodium thio-

. sulfate will convert thesechloramines to ammOnia.

c Certain o r ga ni cs mayproduce an off color withNessler's reagent. Ifthese compounds are not

u


steam distillable. ,nterferenremay be eliminated distillationmethod.

d Many organic and inorga..,.. 4-1poond,cause a turbidity interfere ',iscolorimetrio test. Therefor. -tnesslerization is not a recop.,.-:

.4hod. The following diet',ocedure is a required, pr

..1 -nent.

,r1 (8' 7. 8)

I ft, .

Ft.: sample is distilled in..a.eaence of a borate

uuffer at pH 9.5

NH4 4 NH3 + 11+

li+ + Na2 B407 pH 9.5 maintainedBuffer

The ammonia in the clf e-tillat a is then measured byeither of two techniques.

1) Nesslerization tensedfor samples nmtainingless than 1 ofammonia nitrogen. (6. 7.

2) Absorption of NH3 byboric acid Ind back ti-tration with a staroard

ong acid is mare.suitable for samplescontaining more thiin1 mg NH3N/1 (6. 7. 8)

NH3 +HB02---o- "114+ B02"

B02" + H+ HBO2

Methylene BluepH 7. 8 - 8.0 PH 6. - 7.0

Green Purple

18-3

8)


2 Interferences

a Cynate.may hydrolyze. Len atpH 9.5.

b Volatile organics may come over inthe distillate. causing an off-colorfor Nesslerization. Aliphatic andaromatic wakes cause positiveinterference by reacting in the acidtitration. Some of these can beboiled off at pH 2 to 3 prior,todistillation.

c Rest Ina' chlorine must be removedby pretreatment with sodiumthlosulfate.

d If a mercury salt was used forpreservation. the mercury ionmust be complexed with sodiumthiosulfate (0.2 gl primer to distil-lation.

3 Precision and Accuracy(8)

Twenty-four analysts in sixteenlaboratories analyzed natural watersamples containing the followingamounts of ammonia nitrogen:0.21. 0.28. 1.71. and 1.92 mgNH3 -N /liter.

a Precision

The standard deviation was: 0.122.0.070, 0.244, and 0.279 mgNH3-N/liter. respectively.

b Accuracy

The bias was -0.01. -0,05.+0.01, and -0.04 mg NH3-N/liter.respectively.

C Selective Ion Electrode(8)

1 Principle

A hydrophobic. gas-permeable mem-brane is used to separate the "samplesolution from an ammonium chlorideinternal solution. The ammonia inthe sample diffuses through the

*13-4

membrane and alters the pH of theinternal u.dution, which is sensed bya pH electrode. The constant level ofchloride in th-. internal solution iserased by a chloride selective ionelectrode which acts as the referenceelectrode.

2 Interferences

a Volatile amines are a positiveinterference.

b Mercury forms a complex withammonia so it should not be usedae a preservative.

,3 Precision and Accuracy

In a sinch laboratoi., (EPA) four surfacewater samples were analyzed containingthe rollowing amounts of ammonianitrugon: 1.00. 0.7":, 0.19, and 0.13 mgNE3-N/lit .

a Precirior,

The standard devil ions were 0.038,0.017, 0.607. . d 0.003 mgNH3-Nfliter, respectively.

b Accuracy

The To Tv-owe*, or. the 0 '9 and 0.13concentration:. was Si.i% and 91%respectively.

1) NPDES Ammonia Methodology

Manual distillation is r,,t rewired fr compara-bility data on representative efflue.,t samplesare on company file to show that thie prelimin-ary distillation is not deceq,iary. However.manual distillation will be required to rese.-,eany controversies.

- 'Neaslerization, titration. and the select ionelectrode are all recognized metheds. Theautomated phenolate method is also ,,ited.

IV DETERMINATION OF NITRITE

A Diazotization(6, 8)1 Reaction

a Under acid conditions, nitrite ionsreact with sulfanilic acid to forma diazo compound.

88


b The diazo compound then coupleswith o-naphthylamine to form anintense red azo dye which exhibitsmaximum absorption at 540 nm.

r Diazotization of Sulfanilamide

NH2

,"`\

SU FANILICA6ID3

Coupling

N

+NO ; + 2H+pH 1.4

91.

N

+ 2H20

S°311

DIAZONIUM COMPOUND

pH2.0 -2.5

2 Interferences

a

b

N

SO 3H

reddish-purple azodye

There are very few knowninterferences at concentrationsless than 1000 times that ofnitrite.

High alkalinity (greater than800 Mg/liter) will give low resultsdue to a shift in pH.

c Strong oxidants or reductants inthe sample also give low restate.

3 Precision

On a synthetic sample containing0.25 mg nitrite nitrogen/ 1, the ARSWater...Minerals Study (1961) re-portid 125 results with a standarddeviation of *0.029 mg/I.

8'9

B NPDES Nitrite Methodology

The colorimetric diazotization method.either manual or automated. is the onlyone cited in the Federal Register.

DETERMINATION OF NITRATE

A Brucine Sulfate(8.7.8)

1 Reaction

Brucine sulfate reacts with nitratein a 13N sulfuric acid solution toform a yellow complex which ex-hibits maximum absorption at 410 nm.Temperature mintrolof the colorreaction is extremely critical.The reaction does not always followBeer's Law. However, a modifica-tion by Jenkins. and Medsker(2) hasbeen developed. Conditions arecontrolled in the reaction so thatBeer's Law ii followed for concen-trations from 0.1 to 2 mg nitrateN/liter. The ideal range is from0.1 to 1 mg NO3-N/liter.

2 Interferences

a Nitrite may react the same asnitrate but can be eliminatedby the addition of sulfanilic acidto the brucine reagent.

b Organid nitrogen compounds mayhydrolyze and give positive inter-ference at low (less than 1 mg/1)nitrate nitrogen conct.ntrations.A correction factor can be deter-mined by running a duplicate ofthe sample with all the reagentsexcept the brucine-sullanilic acid.

c Residual chlorine may be eliminatedby the addition of sodium arsenite. -

d Strong oxidizing or reducing agentsinterfere.

e The effect of salinity is eliminatedby addition of sodium chloride wthe blanks, standards and samples.

13-5


Precision and Accuracy(8)

a Tuenty-seven analysts in 15 lab-oratories analyzed naturalwater samples containing thefollowing increments of inorganicnitrate: 0.16. 0.19. 1.08 and1.24 mg N/liter.

b Precision results as standarddeviation were 0.092. 0.083.0.245. and 0.214 mg N/literrespectively.

e Accuracy expressed as bias was-0.01. + 0.02, + 0,04 and + O. 04mg Witter. respectively.

II Cadmium Reduction(8 8)

Reaction

A nnit-turbid sample is passed througha coluuu, granulatedcopper-cadmium to reduce nitrateto nitrite. The nitrite (that originallypresent plus reduced nitrate) is deter-mined by diazotizing with sulfanilamideand coupling with N-(1-naphthyll-ethilenediarnine dihydrochloride toform an intensdy colored azo dyewhich is measured spectrophotometrically.

To obtain the value for only nitrate.more of the non-turbid sample is testedusing the same colorimetrie res. tionbut without passing it through tht re-duction column. The resulting valuerepresents the nitrite originally presentin the sample. Subtracting this nitritevalue for the non - reduced sample fromthe nitrate + nitrite value for the re-duced oample gives the value for nitrateoriginally present in the sample.

2 Interferences

a Build-up of suspended matter inthe reduction column will restrictsample flow. Filtration or floc-culation with zinc sulfate shouldremove turbidity.

b

13-8

High concentrationscopper or otherinterfere. EDTA iscomplex these.

iron.may

ed to

e large concentrations of oil andgrease in a sample can coat thesurface of the cadmium. Pre-extracting the sample with anorganic solvent removes oil andgrease.

3 Precision and accuracy(8)

in 11 laboratories. three sampleswere analyzed containing the follow-ing amounts of nitrate nitrogen:0.05. 0.5. and 5 mgNO3-N/liter.

a Precision

The relative standard deviationwas 96.4%. 25.6% and 9.2%respectively.

b Accuracy

The relative error was 47.3%.6.4%, and 1.0 %. respectively.

4 Automated cadmium reduction

Standard Methods(8) and the EPA MethodsManual(8) contain details for the autmated pre ledure.

C Hydrazine 11,,..oction

A method using hydra_ Lae reducenitrate to nitrite folic-wed by subsequentmeasurement nitrite by diazotizationwas reported ray Fishman, et al. (I)

The means to letermine nitrate is the"same as above in the Cadmium Reduction

. Method. Subtraction of nitrite (deter-mined from non-reduced sample) fromthe total nitrite (reduced nitrate +original nitrite) will give the originalnitrate nitrogen concentration.

The procedure was adapted to the AutoAnalyzer by Kamphake. et al. '3)It is available from EnvironmentalMonitoring and Support Laboratory.U.S. EPA, Cincinnati. Ohio. 45268.

Ammonia, Nitrites and Nitrates

D Compliance Nitrate Methodology1 NPDF-SjCertific'ations

The Federal Register lists the brucinesulfate, cadmium reduction and auto.,mated cadmium reduction or hydrazinereduction methods.

2 Drinking Water

The Federal Register lists thebrucine sulfate and the manualcadmium reduction methods only.

REFERENCES

1 Fishman, Marvin J., Skougstad, MarvinW.. and Scarbio. George. Jr. Diazotiza-tion Method for Nitrate and Nitrite. JAWWA56:633-638 May, 1960.

2 Jenkins, Davi' and Medsker. Lloyd L.Brucine Metl.ad for Determination ofNitrate in Ocean, Estuarine and FreshWaters. Anal. Chem. 36:610-612.March. 1964.

Kamphake, L. J., Hannah. S. and Cohen. J.Automated Analysis for Nitrate by HydrazineReduction. Water Research. 1, 205. 1967.

4 Lishka. R. J., Lederer, L. A.. andMcFarren, E. F. Water Nutrients No. 1,Analytical Reference Service 1966.

5 Sawyer, Clair N. Chemistry for SanitaryEngineers. McGraw-Hill Book Co..New York. 1960..

6 Standard Methods for the Examination ofWater and Waste Water. APHA. AWWA.WPCF. 14th Ed. 1976.

7 ASTM Book of Standards. Part 31. 1975.

8 Methods for Chemical Analysis of Water &Wastes. EPA-MDQARL, Cincinnati. Ohio45268. 1974.

91

This outline was,prepared by B. A.Punghorst. former Chemist, and C. R.Feldmann. Chetniet, and updated by A, D.Kroner. Chemist, National Training at d'Operational Technology Center. MOTE),OWPO, USEPA, Cincinnati, Ohio 45268

Descriptors: Ammonia, Chemical Analysis;Nitrates, Nitrites, Nitrogen. NitrogenCompounds. Nitrogen Cycle, Nutrients.Water Analysis, Water Pollution Sources

13-7

SOLIDS RELATIONS IN POLLUTED WATER

I MPN, oxygen demand, and solids havebeen major water pollution control criteriafor many years. This discussion is con-cerned primarily with solids and their inter-relations with oxygen demand.

A Engineered treatment or surface waterself-purification depends upon:

1 The conversion of soluble or colloidalcontaminants into agglomerated massesthat may be separated from the water.

2 Oxidation of putresciblr componentsinto stable degradation products.

3 Item 1 is the major concern in mosttreatment systems because item 2requires a greater investment in time,manpower and capital costs.

El Stress on oxygen demand removal fre-quently results in an unduly small amountof attention to the contribution of solidsin the oxygen demand picture.

1 Oxygen demand formulations generallyare specified to be applicable in theabsence of significant depositirn.

2 Increasing impoundment, tidal estuaries,and incomplete solids removal, gener-aliy ensure that solids deposition will besignificant.

3 The HOD test stresses the fraction ofoxygen demand that is exerted r.lativelyrapidly. It includes only the fraction ofunstable material that Is exerted undertest conditions - usually shoit term un-der aerobic conditions.

4 Contributions of a bed load of solids tooxygen demand frequently are incom-pletely recognized because they have a.more local effect, are difficult to measure,tend to move, and are incompletely Un-derstood. The onset of an aerobic actionin deposited solids increases hydrolysisrate. High molecular weight cell'masssplits into small molecules that are

PC.8d.11.7792

soluble and more available for highrate oxidation upon.fiedback into oxy-gen containing water.

II A given wastewater may have severalforms of solids in changeable proportionswith time and conditions.

A Solids may be classified among the chartedforms according to biological. chemicalor physical properties. It is not possibleto precisely classify a given material intoany one form because they usually aremixtures that may Include or be convertedinto other forms.

B Interrelationships are indicated by diagramIn Figure 1. Some changes occur morereadily than others.

1 Settleable solids generally consist ofa mixture of organic, inorganic, en-trained. dissolved or colloidal solidsand living and dead organisms.

a They may be hydrolyzed into smallersizes to aquire colloidal ordissolved characteristics.

b They may be converted into a largerfraction of living material or viceversa.

2 Colloidal solids also are likely to be amixture of organic and inorganicmaterials, living or dead containingassociated dissolved materials.

a They are likely to agglomerate toform settleable masses with timeor changing conditions.

b Chemical reactions may solubillzethe colloidal masses for recombina-tion into other forms.

3 Dissolved solids are the most readilyavailable of all forms for biological.chemical or physical ockiversion.

19-1

Solids Relations in Polluted Water

Figure I. SOLIDS INTERRELATIONSHIPS IN WATER

a They may be assimilated into cell.mass to become colloidal during astate of rapid growth or form settle-able masses during slow growth.Surface phenomena are likely to en-courage inclusion of other forms ofsolids with cell mass. '

C Stabilization occurs with each conversionbecause energy is expended with eachchange. /1 Biological changes involve oxidation to

obtain enough energy to synthesize cells.

t14-2

93

a PAducts consist of cell Mass anddegradation prOducts.

b Oiddation tends toward productionofiCO2. H2O. N05. SO4-2etc. CO2luis limited water solubllity.andpirtinlly leaved the aqueous environ-ment. More soluble constituentstend to remain with it for recycle.

c Biological residues tend to recycle.Eventually the mass consists ofrelatively inert and largely insolu-ble residues. These make up the

. Solids Relations in Polluted Water

bed load that May decompose at arate of less than 1% per day, butaccumulates in mass until it be-Comes dominant in water pollutioncontrol activities.

III Treatment is an engineered operationdesigned to utilize events in surface waterself-purification in a smaller package interms of space and time. Effective treat-ment presupposes oxidation either in theplant or in facilities to minimize feedbackof solids components to the aqueousenvironment. .

A Primary treatment consists of a separationof floatable or settleable solids and re-moval from the used water.

Prompt removal is essential to minimizereturn of solubilized or leached materi-als from the sludge mass.

2 Sludge and scum are highly putrescibleand difficult to drain.

3 Subsequent treatment prior to disposalserves to enhance drainability,and reducesolids or volume for burial or burning.

1:1 Secondary treatment generally involvessome form of aerobic biological activityto oxidize part of the colloidal and dis-solved contaminants and conver most ofthe remainder into a settleable sludge.

1 Aerobic systems favor ass:foliation ofnutrients into cell mass at the expenseof part of the available energy repre-sented by oxidation to products such asCO2 and water.

2 Cell mass and intermediate degradationproducts are only partially stabilizedand tend to recycle with death and decay.

3 Rapid growth of cells tends to produceSludges that are highly hydrated anddifficult to concentrate:

4" A compromise must be reached to pro-duce a favotable balance among separa-tion of solids and feedback of lysedmaterials.

94

a Cell growth continues as long asenergy and nutrients permit.

b Under limiting nutrient conditionsthe population may show a relativelylow rate overall dieoff but varietyis changing.

c Species most favored by the new Con-ditions tend to grow while othersdie, lyse and release part of theirstored nutrients for subsequent use.

C Anaerobic digestion of solids separatedduring treatment is one prpcess used toincrease solids stability and drainabilitywhile reducing total volume or mass fordisposal.

1 Growth of cell mass is relatively slowunder anaerobic conditions while hy-drolytic cleavage is relatively largein comparison to that during aerobicmetabolism.

.a Feedback to the aqueous environmentrepresents a significant fraction ofthe input in the form of ammonia,colloidal solids, low molecularweight acids, and other products.

b Mass of the sludge is reduced by thefraction of methane, carbon dioxide,and other gases produced in process.

c Remaining solids tend to be mornconcentrated, are lower in putresci1bility and give up their water morereadily.

2 The liquid fraction of the products re-maining after anaerobic digestion con-tain nutrients, oxygen demand, solids,and malodorous constituents that areobjectionable in surface waters if.re-leased without further aerobicstabilization.

3 Digester liquids are much :core con-centrated than raw sewage and nutrition-ally unfavorable, hence they are difficultto treat and tend to shock aerobictreatment processes.

14-3.

Solids Relations in Polluted Water

D Suitiable disposal of solids resulting fromtreatment operations takes various formsof which the most desirable Le to oxidizeit completely to gaseous products of oxi-dation or inert ash. The objective is tolimit feedback into the aqueous environ-ment and delay the charted interchanges.

1 Deposition of sludge as a cover on cropland is effective providing surfacedrainage is properly designed to limitwashoff.

2 Burial in areas above the 'flood plainprovides a suitable disposal.

3 Incineration under controlled con-ditions to produce complete burningof organics is effective but requiresclose control.

a Incineration of digested sludge isfeasible but tha digestion processresults in removal of part of theheat content of the sludge as meth-ane. cattbon dioxide and water. Auxilary heat may be required for waterevaporation if solids concentration isbelow 25%.

b Raw sludge incineration relievesthe au: diary heat problem but stor-age may lead to odor problems. Theraw sludge may require chemicaltreatment to enhance dewatering.Secondary sludges are more diffi-cult to dewater and may requirecentrifugation, floatation, or othertreatment to concentrate the sludge forheat balance purposes,

c Incineration requires close controlof complex equipment to maintainacceptable environmental control.Usually. after-burners and off-gasscrubbers are necessary to avoidair pollution.

14-4

IV NPDES METHODOLOGY FOR SOLIDS

In the Federal Register "List ofApproved Test Procedures" for NPDESrequirements there are file classifica-tions of solids listed as "residues" withone method to determine each:

A Total Residue. mg/liter

Gravimetric 103-105.c(1)(2)

B Total dissolved (filterable) residue.mg/liter

Glass fiber filtration 180 c'11:2)C Total suspended (non - filterable) residue.

mg/liter

()lass fiber filtration 103-105°C(1) (2)

Total volatil,residue. mg/liter

Gravirnetric 550°C (1) 121

E Settleable residue, ml/liter or mg/literVolumetric or gravimetric(1)

REFERENCES

1 Standr.rd Methods for the Examination ofWater and Wastewater. APHA, AWWA.WPCF, '14th Ed. 1978..

2 Methods for Chemical Analysis of Waterand Wastes. EPA-AQCL, Cincinnati.Ohio 45288. 1974.

This outline was prepared by F. J. Ludzack.former Chemist, National Training Center.MOTD. OWPO. USEPA, Cincinnati, Ohio 45288.

Descriptors: Anaerobic Digestion. Oxygen.Oxygen Demand, Sludge, Sludge Disposal,Sludge Treatment. Solids, Waste WaterTreatment, Water Pollution Sources

95

TURBIDITY

I INTRODUCTION

Turbidity age wear quality index refersto the deiFelof.cfoudineds present.Conversely, it is an index.of clarity.

. .A Definition(1)

Turbidity is an expression of the opticalproperty that causes light to be scatteredand absorbed rather than transmitted instraight lines through samples of water.

B Relationship to Suspended Sol'xis

This optical property, turhidity, iscaused by suspended Matter. The size.sha,Je and reflection/absorptionproperties of that matter (not its weight)determine the degree of optical effects.It is very possible to have water withhigh turbidity but very low mg/1 sus-pended solids. Thus one cannot use ,

turbidity results to estimate the weightconcentration and specific gravity of thesuspended matter.

C Causes

1 clay, sand

2 silt. erosion products....

3 microscopic and macroscopicorganisms..

4 finely divided organic products

5 others

D Effects on Water Quality f21

Turbidity is an indicator of possiblesuspended matter effect() such asimpeding effective chlorine disinfectionand clogging fiskgills. However, thefollowing list is limited to those effectsassociated with the optical (clarity)nature of turbidity.

CH. TURA. 2.11.7793

. .

1 RedUcini'clarity in water

a drinking water qualityb food processing 'c industrial processesd fish (seeing natural food)-e 'swimming/water snorts

2 Qhscuring ..biects innvater

a wsuabmergedthaza.r.dswater sports

3 Light penetration

a affects depth of compensationpoint for photosynthetic activity(primary food prop-46110n).

4 Thermal Effects

High turbidity causes near surfacewaters to becomeheatbd because of.the heat absorbency of the particulatematter.

Results in lower raterof oxygen'transfer from air to water.

b Stabilizes water coldnin andprevents vertical mixing.

1 decreases downward dispersionof dissolved oxygen

2 decreases downward dispersionof nutrients

E Criteria for Standards (2)

I Finished Drinking Water - Maximumof one unit where the water enters thqdistribution system. The proposed"'standard is one unit monthly average andfive units average of two consecutive days.Under certain conditions a five unitmonthly average may apply at state option.

2 For Freshwater Aquatic Life andWildlife - The combined effect of colorand turbidity should not change the

15-1

Tur6tdity'

compensation point more than 10%from its seasonally establishednorm, nor should such a changeplace more ...aari 10'r0 of the biomass ofphotosynthetic organisms below thecompensation point.

i Turbidity Cr,.teiia Used by Industries:

a Textiles - 0.3to 5 units

b Paper and allied products - Rangesfrom 10 to 100 units. depending ontype of paper.

,c Canned, dried and frozen fruits andvegetables - Same as for finisheddrinking water (I turbidity unit).

Processes to Remove Turbidity (Sulids)

i Coagulation

a pre-chlorination enhances coagulation

2 Sedimentation"

3 Filtration

-4 Ae rlation

5 Others

II VISUAL METHODS TO ESTIMATETURBIDITY

A Early Efforts

In the early I900's. Whipple and Jacksonmeasured turbidity and developed a calibra-tion scale for turbidity instruments.

El Jackson Candle Terbidimeter

Later Jackson developed apparatuswhich utilized 'De same "extinction'.principle as the instrument devised:earlier with Whipple.'

'115-2

. I Instrument

9r

Figure 1 JACKSON CANDLEtusSIDDAETER

nThe sample was poured irIO a flat-bottomed, graduated glass tubeheld over a special candle. Aturbidity reading was taken whenthe operator. observing from thetop of the tube. saw the image of thecan.ile flame disappear into a uniformglow. The reading related the finaldepth of sample in the tube with tubecalibrations obtained from a standard'suspension solution.

2 Statiard SuspFision

Tiro standard was a suspension ofpreparedfrom Fuller's or

dia`c.-,ceous earth. This wasdi' .. rrepare a series ofstanuu u suspensions to graduatethe Sur ci r..metr r. Graduations on allJackson 1...,10.4,:gria.t.x.'s are made inconformity to u1± vrLgiv,....; data.Other suspensions are stindardized by.using the pre-calibrated turbidimeter anddiluting according/;.

3 Unit Used

Jackson Turbidity Unit 1J11.11 - partsper million suspended' silica turbidity.

Turbidity

4 Standardization of Apparatus

The current edition ofSta.ndand

Iethods (1) contaihs'specifications .

for the three essential components....i.e.. the e-ilibpated glass toy. thecandle anci,anApport.

5 Current Standard SuspensionSolutions( 1)

AP'

, 1 Natural turbid water from the Samesource as that tested givee..bestresults. Determine turbidity withthe instrument. then Ailute to valuesdeStred.

2 The supernatant of a tsettled solutionof kaglin is also usedl as a standa5d.

6 Limitations of Method

a Apparatus - difficult to exactly,reproduce flame as to intensity andactual light path length. In general,it is a rather crude instrument withseveral variables that affect accuracy.

b Very fine suspended Articles dd nottend to scatter light of the longerwavelengths-produced by the candle.

o Very dark and black particles canabsorb enough light in comparison

to the scattering of light to causean incorrect reading of imageextinction.

d Turbidities below 25 JTU cannotbe directly measured. or lowerturbidities(as in treated waters).indirect secondary methods arerequired to estimate turbidities.

C Ilellige Turbidimeter(4)

Thiq instrument utilizes the sameextinction principle as the JacksonCa turbidimeter.

Equipment

An.opal glasis bulb supplies the lightwhich is reflecte-J (usually through a

.

filter) upward through the samplewhichis contained in a glass tube.The entire system-is enclosed in ablack metal box. The operate- vie,the sample by lookliig downwari:.th-augaan ocular tube screwed into the top ofthe box and'adjifsts the brightness of acentral'fiald of light by turning a .calibrated dial on.the outside of theapparatut The point of uniform lightintensity occurs when a black spot inthe center of thr 1ielcijust disappears.

I2 Range ofAppliez

The equipment offers a choice of bulbs.filters and ,,Iumes:of sample tubes.The variety affordsa.meana to directlymeasure turbidity ranging from 0 through150. The ranges can be extended bydilution.

3 Results

The final ^eading from the dial is- translated into ppm silica turbidity

by using a graph corresponding to dubulb. filter an volume of sample.usen.

4 ,Standard Suspension SobitiOn

Standardizing suspensions are not.usepby the operattir. The graphs aresupplied by th.e company for eachinstrument.

D Seccht. Disk (5)

This is a very simple device used inthe field to estimate the depth of visibfift(clarity) in water.

I Equipment

, The disk is a weighted 'circular plate.20 cm in diameter, with opposing blackand mate quarters painted 'on the surface.The plate le attached to a calibrated laneby means of aring on its center to assurethat hangs horizontally.

2 feax-i gs

T', disk is lowered into water untiliappears, lowered farther, then

15-3

Turbidity

raised until it reapp:a..-s., Thecorresponding visibility depth (s)are determined from thecalibrated line: Some read bothdepths and average them. Someread only the reappearance depth,

3 Standardizing the Pro.edure

'there are many variables (positionof sun and of observer. roughness ofbody of Water, etc.) that affect

.eeadings. llowever; the same -observer using a standard set ofoperating conditions can provideuseful data to compare-the visibi ;of different.hodies of water.

4 Application of Results

Litnnologists have found itconvenient to establish a Secchidisk "factor"'for estimating thephotic depth.where light intensity /

is about I per cent of full sunlightintensity. The true photic depth isdetermined by use Of a submarinephotometer and at the same timethe observer -kes a series ofSecchi disk sings to obtSinaverage. Div' ag the true IS i;tiodepth by this average' givesfagtor which can be userl to multiplyother disk readpgs fu approxima-tion of photic depth.

E Status of Visual Methods for Compliance:Monitoring

The Federal Ftgister(6) "List ofApproved Methods" does not includeany se visual methods for National

.; Discharge Elimination SystemNPDES) requirements. The visual

methoes are not recognized in theFederal Register") issue on interimD:'Mking Water Regulations, either..

15-4

4

Ill rlEPHELOMETRIC MEASUREMENTSFOR COMPLIANCE MONITORING

The subjectivityand apparatusdeficiencies involved in. visual methodsof measuring turbidity make eachunsuitable as a standard method.

Since tbrbidity is an expression of thetical prOperty of scattering or

absciklaing light, it was natural thatopticainstruments with photometerswould be developed for this measurement.

The type of equipment specified forcompliance monitoring13' 6) utilizesn7helornetry,

A Basic Principle(?)

The intensity alight scattered by,thesample is compared (under definedconditions) with the intensity of lightscattered by a standard referencesolution fformazird. The greater theintensity of scattered light, the greaterthe turbidity. Readings are made andreported in'NTUs (NephelometricTurbidity Units).

II Schemata.

phok4.140

K

1,11.Scat. 1.40,,,

ample CIlIron V441

figure 2 NEPHELOMETER(90° Scondir)

Light passes through a polarizing lensand on to the sample in a cell.Suspended particles (turbidity) in thesample scatter the light.

#

'Turbidity .

Photo.-ell Is) detect tight scatters:the particles at a 9fo angle to theof the incident light. This lightenergy is cons erted to an electricsignal.for the meter to measure.

Direction of Entry of Incidentlight tc.Cell

a The lamp might43e positioned asshown in thescnematic so thebeam entersa sample horizontally.

b Another instrument design has thelight beam entering the samplelin a flat-bottom cell) in a-verticaldirection with the photocell_Positioned according at a 90'angle To the path ofincident light.

2 Number of Photocells .The schematic shwas the photocell (s)at one 90 degree angle to the path ofthe incident light. An instrumentmight utilize more than one photocellposition. with each final position being.at a 90 degree angle to the sample liquid.

3 Meter Systems

a The meter might measure thesignal from the scattered lightintensity only.

b The meter might measure thesignal from a ratio of the scatteredlight versus light transmitteddirectly through the Sample to a

. photocell.

4 Meter Scales and Calbration

The meter may already becalibrated icaNTU5. In this case,at least one standard is run ineach instrument range to be usedin order to check the accuracy ofthe calibration scales.

-"a

h If a pre-calibrated scale is not^ :supplied, a calibration curve is -

prepared for ach range of theinstrument la using appropriatedilutions of t e standard turbidity

Pesus nsion.

C t-l)A Specifications for Instrument Design' 7).

Even when the +-a.ne suspension is usedfor calibration al' different nephelometers,differences in physical design of the

s will cause differences inmeasure.) f6r the turbidity of the .

same sample. To minimize such differences.the following design variables have beenspecified by the U. S. Environmental l'rstectionAgency. -

Defined Specifications

a. Light Source

Tungsten lamp operated at not lessthan 85°,1, of.rate-I voltage and at notmore than rated voltage.

b Distance Traveled by Light-

The total of the distance traversedby the iicIdent light plus - scatteredlight within the sample tube shouldnot exceed.I0 cm.

c Angle of Light Acceptance of theDetector

Detector'centered at 90° to theincident light path_and not to exceed+ 30° from 913°.

(Ninety degree scatter is specified .

because the amount of scatter varieswith size of particles at differentscatter angles).

d Applicable Range

The maximum turbidity to bemeafrure I is 40 units. Several rangeswill be necessary to obtain adequatecoverage. Use dilution for samples if

. their turbidity exceeds 40 units.

2 Other EPA Design Specifications

a Stray light ,

Minimal stray light shoat] reach thephotocell (S) In tha absence of turbidity.

1U 15,5

Turb:ditv

15-6

Some causes of stray light reachingthe photocell Is) are,

1 Scratches or imperfections inglass Cell windc.ws.'

2 Dirt. film or condensation on theglass.

Light leakages hi the instrument.system.

A schematic of these causes isshown in Figure 3.

ym Scam. by 5an. ruesi.eI

Figure 3 NEPHELOAtETER

SOURCES OF STRAY LIGHT

Steay light error can be as muchas 0.5 NTU. Remedies are closeinspection of sample cells forimperfections and dirt, and gooddesign which can minimize theeffect of stray light by controllingthe angle at Which it reaches thesample.

b Drift

The turbidimeter should be fraefrom significant drift after a shortwarm-up period. This is imperativeif the analyst is.relying on a manu-facturer's solid scattering standardfor setting overall instrumentsensitivity for all ranges.

c §ensitivity

In waters having turbidities less thanone unit, the instrument should detect

turbidity differences of 0.92 unitor less. Several ranges will benecessLi, to obtain sufficientsensitivity for low turbidities.

3 Examples of instruments meeting thespecifications listed in I and 2 aboveinclude;

a Hach Turbidimeter Aloilel 2100 and2100 A

b Hydroflow Ifistruments DRT 100. 203.and 1000

4 Other turbuill,stevs(12) meeling thelisted specifications are alsoacceptable.

13 Sources ofEreur

I II.larred Sample Cells

a Discard scratched or etched cells.

b Do not touch cells where lightstrikes therzi in instrumcpt.

c Keep cell clean. insideand out.

I Use detergent solution.

2 Organic solvents may also be-used.

3 Use ileionized water rinses.

4 Rinse and dry with alcohol oracetone.

2 Standbrdizing Suspensions1(a use turbidity - free water fpr

preparations. Filter distilled waterthrough a 0.95 u m pore size membranefilter if such filtered water shows alower turbidity than the distilled water.

b Prepa a new stoclisuspension ofFor zin each month.

c Prepare a new standard suspensionand dilutions of Formazin each week.

101

Sample Interferences

a Positive

I Finely divided air bubbles,

b Negative

Floating debris

2 Coarse sediments (settle)

S Co lones'_ dissolved substances!absorb light)

4r E Reporting Resultsr"

NTL' Record to Nearest:

0.050.0-1.0 "v

1-10

10-40

40-100

100-400

400 -1000

>1000

F Precision and Accuracy

0.1'

5

\.10

50

100

(7)'.

c

1 In a single laboratory (MDQARL),using surface water samples atlevels of 26. 41. 75 aqd 180 NTU.the standard deviations were + 0.60.+ 0.94. + 1.2 and + 4.7 units,respectively.

2 Accuracy datis not available atthis time.

IV STANDARD SUSPENSIONS AND RELATED

UNITS(9)

One of the critical problems in measuringturbidity has been to find a material whichcan be made into a reproducible suspen-sion with uniform'sizedparticles. Variousmaterials have been used. .

A Natural Materials-1 Diatomaceous earth.'

2 Fuller's earth

Kaolin

Turbidity

4 Na:ir;11v turtitl waters

Such suspensions are not suitaikeas reproducible standards because thereis no way to control the, size of thesuspended particles'..

B Other ,Materials

1 Ground glass

2 Microorganisms

3 Barium sulfate

4 Latex spheres

Suspensions df these also provedinadequate.

C Forrnaain. .

1 'A polymer formed by reacting hydrazinesulfate and hexamethylenetetraminesulfate.

2 It is more reproducible than previously-used standards. Accuracy of + one percent for. replicate solutions has beenreported.

In 1958. the Association of Ant lyticalChemists initiated a standardized.systeinof turbidity measurements for the brewingindustry by:

^ a defining a Standard formula for makix astock Formazin Solutions and

b designating a unit of measurem'ent".based on Formazin, i.e.: the FormazinTurbidity Unit (FTU). . ,

4 .ng the 1960's Formazin was increasing-ly used for water quality turbidity testing.It is'the currently recognized standard forcompliance turbidity measurernents.

.1U;;. tr

15-7

Turbidity

-D Units

1 At first results were translatedinto. Jackson Turbidity. Units1.7Tr1. However, the JTU wasderiyed from a visual dneasurementusing concentrations (tngniter) ofsilica suspensions prepared byJackson. They have no directrelationship to the intensity oflight scattered at 90 degrees ina nephelometer.

.02 For a few years. restate of

nephelornottric measurementsusing specified Formazinstandards were reported directlyas Turbidity Units (TU's).

3 Currently.. the unit used is named-according to the instrument used formeasuring turbiAtfy7 SpecifiedFormazin st4gataids are used tocalibrateple instrument and resultsare reported as NephelometricTurbily Lfiits (NTUs).

V TII:RBIDITY MEASUREMENTS FORPROCESS CONTROL

The schematic and design'characteristicsdiscussed above for nephelometricinstruments is the req 'red methoc formeasuring turbidity for compliancepurposes. Turbidity data is also widelyused to check water for process designpurposes and to monitor water for processcontrol purposes. The nature of theliquids to be monitored. and the degree ofsensitivity required for signalling the -remedy to be applied have led to thedeverVment of monitoring instrumenta-tion that differs in design or in principlefrom the instrument previously described.

A Users if Control Data

1 Potable Water Treatment Plants

2 Municipal Wastewater Treatment Plants

3 ,Industrial Processers

a

15-8

4

inApplications of Control Data

t 11)

I Coagulation processes'

a To checKthe effectiveness ofdifferent coagulants.

b To check the effectiveness ofdifferent dosages.

To regulate chemical dosages byautomating chemical feed controls.

2 Settling Processes

a To determine intermittent need forsettling processes.

b To control the sludge blanket heightin activated sludge trf atment processes.

c To activate removal and re-cycling ofvery high density.'sludge from settlingtanks.

d To monitor effectiveness of settlingprocesses.

fr?

3 Filtration Processes

a Tq determine intermittent needfor filtration.

b To facilitate high rate filtrationprocesses.

c To prevent excessive loadings forfiltration systems.

d To check the efficiency of filtrationsystems.

To regulate filter backwash operations.

4 Rust in Wrter Distribution Systems

a To locate sources of Contamination.

b To monitor intermittent occurrences.

5 Steim Boiler Operations

a To detect corrosion products inboiler water.

1 0,3

Turbidity

b To detect evidences of corrosiorTM_ is difficult to achieve in glass cells.in condensates.

c To determine the effectiveness ofcorrosion treatment measures.

C Varieties of Instrumentation

1 Surface Scatter Neptielometeili

In forward - scattering instruments,the angle of the incident light isadjusted to illuminate the surfaceof a smooth flowing liquid at an angleof about 15 degrees from horizontal.rather than beamed through a glasscell of the'iiquid as .'escribed for anephelometer earlier in this outline..A photocell is located immediatelyabove the illuminated area so thatvertically scattered light fromturbidity in the sample reaches it.

iiia

1..b.jih_r I I

.5.01 lyM

Ij

e.

le,ure4 NEPHELOmEfER (Surface Scatter)

Variations of the methodology' Iinclude sidescatter and backscatterdesigns.

a Advantages

1 No glass sample cells areused. Attendant problems ofcleanliness and condensationare eliminated, The surfaceof the liquid provides a near.perfect optical surface which

2 Stray light effects on tue photoCellare minimized because the simplerdesign eliminates son% of the sourcesof stray light.

3 Since flowing sample is used,interferences from air bubbles and/or floating materials are quicklyeliminated.

4 This design is sensitive to the presenceof larger suspended particles.

b Disadvantage

As turbidity becomes high, penetrationof incident light decreases to cause afalling off of response.

2 Absorption Spedtrophbtometry

The incident light is beamed through asmooth, flat stream of sample and thetransmitted light (in contrast tonephelometric scattered light) is measuredby a spectrophotometer. A schematic .is shown in Figure 5.

Urbidity Parti<1011 L6006./.

a

Figure S ASSORPIION SPECTIOPHOTOMETRY

a Advantages

1, l'o glass sample cells are used.

2 The 'simpler design eliminatessources of shay light.

3 Applicable to measure highturbidities.e.g., in sludges.

b Disadvantage

1 Low sensitivity for many applications,

2 Color constituents interfere.

15-9

Turbidity

V 1 ARC

Turbidity measurements represent theoptical property of light scattering bysuspended solids. NTUs are an. index -of the effects of the size. etc.. ofsuspended particles but cannot be usedto indicate mg/1 quantities of those''particles. The parameter is requiredfor finished potable water and is extreme-ly useiuLin reference to aesthetic quality

photic conditions and thermaleffects in bqdies V water. It is aliowidely applied for process control ofwater and wastewater treatment andof industrial processes.

There have been difficulties in developinga satisfactory standard method for thismeasurement. Early methods dependedon a subjective judgement of an extinctionpoint where transmitted light balancedscattered Had in rather crude apparatus.Although the apparatud was refined andstandardized to a large extent, thesubjectivity of these visual methods wasstill an unsatisfactory element of such

I methodology.

Eventually. optical instrumentation wasdeveloped to elimina ubjectivityfrom the measurem nt; Nephelometry(scattering) was cho en for the standardmethod'and U. S. E has specifiedseveral instrument des criteria tofurther promote standardizhtion of themeasurement.

Finding a suitable (reproducible)standard suspension has also been aproblem. Currently. Formazin isspecified as the standard because, todate, it is more reproducible thanother suspensions proved to be.

Establishing a meaningful unit progressedalong with development of instrumenta-tion and agreement on a standardsuspension. The current unit (NTU) isderived from the method of measurement.nephelometry. and use of a standardForsgazin suspension.

Even with the efforts to standardize

15-10

instrument design, to find suitablestandard suspension. and toon a meaningful unit, there are tillproblems about this measurement.Instruments meeting thedesignriteria and standardized with

Formazin suspensions can giveturbidity rezt."gs differingsignificantly for the same sample.

Another problem area is associated. with sample dilutions. Work has

indicated a progressive error on ft.sample turbidities in excess-of 40 units,so such samples are to be diluted.However, obtaining a dilute= exactlyrepresentative of the originalsuspension is difficult to achieve.Thus dilutions often significantly failto give linearly decreased resultswhen re-measured.

RETERENCES

1 APHA, h.WWA, WPCF, Standard Methodsfor the Examination of Water andWastewater. 14th ed., APHA,1976.

2 National Academy of Sciences, Nation.'Academj, of Engineering. 1974 EPArevision of Water Quality Criteria..1972. EPA, GPO. Washington. DC20402. /I 5501-00520.

3 U. S. Government. Code of FederalRegulations. Title 40. Chapter 1..Part 141 - National Iriterirn PrimaryDrinking Water.Regulations. publishedin the Federal Register. Vol 40. No. 248.Wednesday, December 24. 1975.

4 Hellige.einc.. Graphs and Directions forHellfge Turbidimeter, Garden City.NY, Technial Information #8000.

5 Lind. O. T. ,. Handbook of, commonMethods in Limnology. Mosby. 1974.

6 U. S.; Government. Code of FederalRegulations. Title 40, Chapter 1,Part 136 - Guidelines EstablishingTest Procedured for the Analysis ofPollutants, published in the 'FederalRegister. Vol 41. No. 232. Wednesday.December 1, 1976.

-105

Turbidity

'7 Methods for Chemical Analysis ofWater and Wastes. EPA -Cincinnati.' Ohio 45268, 1974.

8 Analytical Quality C :enrol in Water andWastewater Laboratories. EPA -AQCL, Cincinnati. Ohio. 1972.

9 News and Notes for the Analyst. HachChemical Company. Ames. Iowa.Volume I. No. 3.

1 0 Sawyer and McCarty. Chemistry forSanitary Engineers. McGraw-Hill.NY, 1967.

This outline was.prepared by Audrey D.Kroner. Chemist. National Training andOperational Technology-Center. MOLD.OWPO. USEPA. Cincinnatf, Ohio5268

Descriptors: Sherhical Analysis.InstruMentation, Secchi disks. Turbidity.Wastewater. Water Analysis

1 1 Turbidimeters. Hach Chemical Company.Ames. Iowa. Fifth Revised Edition.1975.

12 Bausch a.id Lomb andTurner of California areadditional emmtaes (9/77)of Models meeting thelisted specifications.

?g-

.0 3

a15-11

SPECIFIC CONDUCTANCE

ritopucTioN

An e ectrical conductivity measurement of asi,Lilion determines the ability of the solutionto conduct an rlectrical current. Veryconcentrated slIntinns have a lame populationof ions and transmit curr.ni .,.11. or withsmall resistance. Since resistivity isinversely related to conductivity K ft,a very concentrated solution has a veryMO electrical conductivity.

Electrical conductivity is determined by .

transmitting an electrical current throughgiven solution, using two electrodes.. The

resistance measured is dependent principallyupgu the ionic concentration, ionic charge,anet emperatu re of dr solution althoughelectrode characteristics (surface area andspading of electrodes) is also critical. Earlyexperiments in standardizing the measurementled to construction of a. "standard cell" inwhich the electrodes were spaced exactly 1 'cm

. and each had a surface area of 1 cm'. Usingthis cell, electrical conductivity is expressedas " Sp'cific Conductance". Motiern specificconductance cells do not have the sameelectrode dimensions as the early standardcell but have a characteristic electrode spacing/area ratio known as the "cell constant''.

1 distance (cm) 1K Xsp area (cm2) ' sp if

k cell constant

Specific sonduc, anceunits are Mhos/cm orreciprocal ohm's/cm.. Most rafural. freshwaters in the 'United States have specificconductances ranging from 10 to 1, 00611micromhos(cm. (1 fnicrotriho 10 mho).

U 'CONDUCTIVITY INSTRUMENTS

Nearly all of the commei Lai specific con-ductance instruments are of a bridge circuitdesign, similar to a Wheatstone Bridge. .Null or balance. is detected either by metermovement, electron "ray eye" tubes, orheadphones. Since resistance is directlyrelated to temperature, some instrumentshave automatic temperature compensators,although inexpensive models generally havemaral temperature compensation.

Conductivity instruments -.Der direct specificconductance readout when used with a'eell"matched" to thatpartic3ular instrument.

Electrodes within the cell may becomedamaged or'dirty an'd accuracy may beaffected; therefore, it is advisable tofrequently check the instrument readingswith a standard KC1 solution having a knownspecific conductance.

'a CONDUCTIVITY CELLS ,

types 9f conductivity cells area ble, each having general applications.Di" lls.are.generally used for field .measurement, flow cells for measurementwithin a closed system. and pipet cells forlaboratory us'e. Many modificat idns of the

, ab ve types are avallable for specializedoratcry applications: the Jones cells and

inductive capacitance cells are perhaps themost common.

Examples of various cell ranges for the RB3- Ihdratrial Instruments tuodel (0-50micromhos(cm scale range) are in Table 1.

RelativeCell Conductivity

Nuran(r ValueMaximum rangemicromhosi cm

Most accurate rangemicromhos cm

Cel VS02' 1 0 - 50 - 30Cel VS2 0- 500 20- 3t1t)Cel' VS20 - fi000 200 - 3000

. Cll. COND. 2e. 11.77

Table 1

. 16-1

Spetilic Cor.ductance

IV Computatior,oi Calibration Constant

r. calibration constant is a factor to whichscale readings must be multiplied by com-pute specific conductance.

K = ci.11 -spwhere K = actual specific conductancesp

c = calibration constant

M = meter reading

For example, a 0.001 N KC1 solution(147 micromhos/cm standard) may showa scale reading of 147.

7147 = c 1470 c11:7

1. 00

In this case the els' lids perfectly "matched"to the instrument, the calibration constantis 1.00, and the scale reading representsactual specific' conductance. A variety ofcells, each covering a specific range.may be used-with any one instrument.However, a calibration constant for eachcell must be computed before solutions ofunknown specific conductance can bedetermined.

V- RELATIONSHiP OF SPECIFIC CONDUCTANCE TO IONIC CONCENTRATION

Natural water consists of many chemicalconstituents, each of which may differwidely in ionic size, mobility, and solubility.Also, total constituent concentration andproportions of certain ions in various naturalwaters range considerably. However, itis surprising that for most natural watershaving less than 2, 000 mg/l. dissolvedsolids, dissolved solids values are closelyrelated to specific conductance values,

'ranging in a ratio of .62 to .70, Of coursethis does not hold'true for certain watershaving considerable amounts of nonionizedsoluble materials, such as organic com-pounds and nonionized, colloi 1 inorganics.

16-2

Properties of some inorganic ions in regardto electrical conductivity -are shown below:

Micromhis/cmIon per meq/1 conc.

Calcium 52.0Magnesium 46.6Sodium 48.9Potassium 72.0Bicarbonate 43.6Carbonate 84.6Chloride 75 9

VI ESTIMATION OF CONSTITUENTCONCENTRATIONS

Generally speaking.for waters havinradissolved solids concentration of leas than1,000 mg/1, calcium and magnesium (totalhardness), sodium, bicarbonate andcarbonate (total alkalinity), and sulfate arethe principal or most abundant ions;representing perhaps 90-99% of the totalioniec,nceptratien of, the water. Specificconduitan. , total hardnnss and totalalkalinity are all simple and ex;_edigntmeasurements which can be perforrhed inthe field. Therefore, the remaining principa:ions are sodium and sulfate, and concentrationsof these can be estimated by empiricalmethods. For example, we find that a certainwater has:

IC" 500 rnicromhos/cmTotal Hardness 160 mg/1 or 3.20 meq/1Total Alkalinity 200 mg/1 or 3.20 megaas bicarbonate.

Next we multiply the specific conductince by*0.011 (500 X0.011 5.50) to estimate thetotal ionic concentration in meq/1.

* This factor may vary slightly fordifferent waters

Cations (meq/1)

CalciumMagnesiumSodium 5.50-3.20 2.30Total Cations 5.50

3.'20

1 0

Anions (meq/1)-

Carbonate 0.00Bicarbonate 3.28Sulfate 5.50-3.28 2.22Total Anions 5.50

that S.,:lral'I.-.11InitIo, areIII 1.4111, .1..11411\ rests

ou testing tin, fornio.., Pv.ith lotiscoin.. iahoratot lvs.s for that

I. I l,1,81.11I1,111 iSfloal,1 .,nots, auait.tical ,osts tila. is

r1.11.1.1ttII. Eisped; Ilia It st,,.., i,so in, uscO ,11.111.11/.1

I

Specific Conductanoal

D Geology

Stratigraphic identification andchara.teri,tati II

a geological mappingii oif explorations

E Oceanography

I Nlapping111,11,I, of laboratory chetni.-.11 analysts

2 E:stua iery studsIn.nc.r. la: a part icular ste...1111 ora )1.11,1r11.1.ISIIC

IoVtIS. hydrology.< !ht. ..1:17,1.11,1V11,11111,11t altered

I Its new water suppliesyam: ater composgion responds sololv.tohatnral....ausqs, a apecifi, conductivity

ores in occasimully lSed ii a buried stream channels (See Fig. 17l

substautio rn lot ii. bonnet analyse,s to b springs in lakes andstreams (See Fig. 2)determine water quality. Concentration Ill

cwistiruentst,:atI thtui be Laitimatenfrom in specific condo uelance value. 2 Detectiontand regulation if sea tidier

encialachnient on shore wellsVII APPLICATIONS FOIL SPECIFIC .

COI,CDECTANCE )IEASI/REMINTS E Water Quality Studies

A Laboratory (IperatiOns(2) Estimation of dissolved solids 2)(See Section V also lig. 3)

1 Checking purit,t' of distilled and de-ionized water i' , 2 Empirical analysis of 'constituent

concentrations (See Section VI, also2 Estimationof dilution factors for reference 2)

Samples .

3 Quality Control check for salt water3 Quality contitd check on analytical conversion studies

accuracy4 Determination of mixingt.efficiency

4 Alt electrical indicator of streams (Svc Fig. 4)

FL Agriculturel 5 Determination of flow pattern ofpolluted currents (See Fig. 4)

1 Ettaluathilg salinityIi Identification of significant fluctuations

2 Estimating Sodium Adsorption Ratio in industrial wastewater effluents

Industry" 7 Signal of significant changes in thecomposition of influents to w.aste

tt1 Estimating corrosiveness of water in treatment plants

steamf boilers

2 Efficiency check of boiler operation

16-3

Spe'cific Conductance

FIGURE 1DETECTION OF BURIED STREAM CHANNELS

FIGURE 2

DETECTION OF SPRINGS IN LAKES AND STREAMS

MAN LOWERING LAND SURFACECONDUCTIVITY CELL

LAKE OR RIVER

l

Speuific Conductance

1

°sObo

.E

4000

V3000

,s 2000

1000

5(:)00500 1000 1500 2090 2500 3000 3500

DISSOLVED SOLIDS, me /filer

Figuro 3. SPECIFIC CONDUCTANCE AND DISSOLVED SOLIDSIN COMPOSITES OF DAILY SAWLES, GILA RIVERAT BYLAS, ARIZONA, OCTOBER,,t, 1944 TOSEPTEMBER 30,1944.

Geological Survey Wator-Supply Paper 1473.

rottuvrm

16-5

Specit.c Conductance

1 3000

'4' 20004

O

0 1000

10 20 J0 40

TEMPERATURE, C.

Figure 5. SPECIFIC CONDUCTANCE OF A 0,01y. NORMAL SOLUTION OF POTASSIUM

CHLORIDE AT VARIOUS TEMPERATURES.

Geological Survey Waler-Supply Paper 1473.

1600

1400

1200

1000

V

SOS

600

0400

. '.200

16-6

.00 100 200 300' 400 500 600 .100POTA551UM.CHLORIDE, i.5 /firer

Figaro 6. SPECIFIC CONDUCTANCE OF POTASSIUMCHLORIDE' SOLUTIONS.

Geological Survey. Water-Supply/agar 1473

112', .

Specific Conductance

VIII NPDES METHODOLOGY

A The Federal Aegister "List of ApprovedTest Procedures" for NPDES require-ments specifies that specific conductancebe measured with a self-containedconductivity meter. Wheatstone bridgetypein (2) (3)

TemperatuF directly affects specificconductance values Iseei'Fig. 5). Forthis reason.. eau. ,s should preferablybe ani4..j.1 2.°c. If not: temperaturecorre74-8",4 shmi, I he made and resultsreport' 4:.111:11/s/em at 25°C.

1 The instrument should be standardizedusing {XI solutions. (See Fig.6)

2 It is essential to keep the conductivitycell clean.

B The EPA manual specifies using theprocedure as described in Standard

Nlethods(21

or in ASTM Standards (3)

These are approved in 40 CFR136 forNPDES Report purposes.

C Preciiion and Accuracy")0.

Forty-one analysts in 17 laboratoriesalyzed 6 synthetic water samples

containing the following K incrementssp

of inorganic salts: 100. 106. 808, 848,1640 and 1710 micrornhcis/cm.

i

The standard deviation of thd reportedvalues was 7.95, 8.14, 66.1, 79.6,106 and 119 at:Mos/cm respectively.

The accuracy cf the repor,ted values was''-2.0, -0. H. -29.3, -38.5. -87.9 and

mhos/ m bias respectively.

REFERENCES

I Methods for Chemical Analysis of Waterand Wastes.EPA-AQCL, Cir!cinnati.Ohio 45268. 1974. .

2 Standard Methods for the Examination4,t of Water and Wastewater. APHA-AWWA-

Y/PCF.' 14th Edition. 1976.

3 ASTM Annual Book otStandards,; Part 31.i975.

This outline was prepared by John R.Jilstra,Chemist. National Eutrophication ResearchProgram. Corvallis. Oregon with additionsby Audrey D. Kroner. Chemist. NationalTraining and Operational Technology Center.MOTD, OWPO, USEPA. Cincinnati. Ohio 45268.

Descriptprs: Chemical Analysis. Concentration.Conductivity. Dissolved Solids. ElectricalConductance. lens.' Physical Properties. Salinity.Sodium. Specific Conductivity. Sultales, WaterAnalysis. Water Supplies. ,,

16-7

L NdORA TORY PROCEDURE /OR ACIDITY

SCOPE ANt, APPLICATION

A ApplIcaple to surface waters,sewage, and Industrial wastes,particularly urine driatnage andreceiving stream, and other waterscontaining ferrous Aron or otherpolyvalentcationsin the reducedHtarc.

B Range for a 50m1 sample:In to 1000 mg acidity /liter.

11 APPARATUS

A A calibrated pH meter andelectrode(s)

It Hot plate,

111 REAGENTS

'.For a detailed discussion of reagentpreparation, consult REFERENCE 1.

A Hydrogen Peroxide, 30% solution

It Standa'rd Sod urn Hydroxide (0.02N)

C Standard Sulfurs Acid (0.02N)

' D Carbon Dioxide-Free Distilled Water

C 'Add 5 drops of hydrogen 1;erqxicle.

.0 Heat the sample,to boiling and con-'tinue boiling (or 2 to 4 minutes. Insome instances, the concentration offerrous iron in a, sample is such thatan additional amount. cf hydrogenperoxide and a slightly longer boilingtime may be required.

Cool the sample to room temperature..

F Titrate with standard sodium hydroxide(0.12N), using a pH matri, to an endvoint of 8.2

C Record volume of standard alkali' osedin the titration.

V CALCULATIONS

A Acidity, as mg/1 CaCO3..PAM - (CXIMIN50,000

ml sample ..where:

A = vol. of standard alkali used intitration

B . normality of standard alkali

t. volume of standard acid used toreduce pH to,4-'or less

,

IV PROCEDURE") D t- normality of standard acid

A Pipet50m1 of the sample into a 250m1beaker.

0 Measure the p11 of the sample. If thepH is above 4.0 add standard sulfuricacid in 5.0 ml increments to lowerthe p,Il 6.4.0 or less. If the Initialp11 of the sample is less than 4.0, theincrelnental addition cif sulfuric acidis notrequired.

B If it is desired to re ort acidity in,milfequivalents per liter, the re-

' ported values as CaCO3, are dividedby 50, as follows:

Acidity as meq/1 mg /}CaCO3

50

Laboratory Procedure for Acidity,

REFERENCES

1 Standard Methods for the Examina-tion of A,ater and Wastewater,14 ed.. 1976, Ar'HA-A.WWPWPCP,Washington, D. O., 241036, p. 276.

2 Methods for Chemical AqilysisofWater aneWastes, 197ir EPA -mnoAP.L. Cincinnati, Ohio45268, p. I..

isoiThifriewas prepared by AudreyD. Kroner, Chemist, National Trainingand Technology Center, MOTO, OWPO,!NITA. Cincinnati. Ohio 45268

Oast ripto rs: Acids. Acidity,Analytical Techniques. ChemicalAnalysis. Laboratory Tests,Neutralization, Water Anal :sis

17-2

1

LABORATORY PROCEDURE FOR TOTAL ALKALINITY

I REAGENT'S

For detailed discussion of reagent preparation,consult method reference 3.

A Carbon Dioxide - Free Distilled Water

B Standard Sodium-Carbonate Solution

C .Hydrochloric Acid Titrard(0. 02 N)

STANDARDIZATION OF THECHLORIC ACID TITRANT

II

A

B

HYDRO-

Set the 'temperature reading on the pHmeter dial to match the temperature ofthe buffer and sample soluticr,e.

Standardize the pftleter against a 0reference butfer.sniution. Check againsta secondt buffer solution.

C Weigh aAurately0,088 +'0.06-1 g of the"'dried sodium carbonatectud transfer it to 'a k00 ml conical 11,.91t. .

-D /4150 ml of water and swirl to dissolvethe carbonate.

E 'e stirring the solution (magnetic barstirrer), acik the hydrochloric acid

titrant fiom a 100 ml buret until a pH of4.5 is attained.

F Caldulate the normality of the' hydrochloric'acid solution as follows:

'..053 X C

A normality of the hydrochloric acid

B g of sodium carbonate used

C ' ml of hydrochloric acid cohenuned

0.053 milliequivalent weight of Na2CO3

CH. ALIC. lib. 2a. 11.

III PROCEDURE

A Pipette 50 ml of the sample into a 150 mlbeaker.

B Titrite with the hydrochloric acid topH 4.5.

C Calculation

Total alkalinity as mg'of CaCO3/1

A XN X50000B

A ml of standard HC1 titrant

N N of standard HCl titrant

B ml of sample

50 equivalent weight of CaCO3

1006 - converts ml to liters

REFERENCES. .

1 Methodfor Chemical Analysis of Waterand Wastes. EPA-MD0,ARL, Cincinnati.Ohio 45268. 1974, p.3.

2 Standard Methods for the Examination ofWater and'Wastewater, 14th ed. 1978..

3 Book of ASTM Standards Pare 31. 1975.p. 111.

This outline was prepared by C. R. Feldmann.Chemist, National Training and OperationalTechnology Center. MOTD, OWPO. USEPA,

"Cincinnati..Ohio 45288. ' '

Descriptors: Alkalis. n.14spility. AnalyticalTechniques, Chemical Analysis. Laborator'yTests. Neutralization. Water 1nalysis

113

18-1

LABORATORY PROCEDURE FOR TOTAL HARDNESS .

I REAGENTS

A Buffer Solution: .

I Dissolve 16.9 g of NH 4C1 in 143 ml ofconc, NII 40H. 4

2 Dissolve 1.179 g of analytical reagentgrade disodium ethylenediamine, tetra-acetic acid ilihydrate(Na,EDTA2H0)and 0:644 g of MgC1 .61r o in 50 ral ofdistilled water. 2 2

3 itdi the solution from (2) to the solutionfrom (1) with mixing, and dilute to 250ml with distilled water. Addition oasmall amounts. of Na,EDTA2H,0 orMgCln 6H ,,O maybe necessarf to attainexacrequittalence.

4 The buffet Should be stored in a plaSticor resistant glass container tightlystoppered to prevent CO, absorpTionand NH loss. Discard the buffer when1 or,2 MI added to the sample fails toproduce a PH of 10.0 + 0..1 at tfie endpoint of the titration.

B Inhibitor:

C

I Most water samples do not require theuse of an inhibitor. In the presence ofcertain interferring ions, however, aninhibitor may be needed to shdrpen theendpoint color change. Several typesof inhibitora may be prepared or pur-chased. .Sodiprn cyanide, NaCN, is oneof the simple; inhibitors to use. -

2 Add 0,23 e of powdered NaCN to thesampi. :II I (1 ad.ust the pii 10. 0 +0. 1.Caution: Ni.,(2N is poisonous. UseTar7ffirrnoUni; of wa ez,v flushingsolutions containing NaCN down thedrain. Do. not acidify solutions contain-ing NaCN; volatile, poisonous hydrogencyanide, HCN, would be liberated.

Indicator:

1 Eribchrone BlaCk- dye (EBT) is use-ful for the determination. Other 'comelier-cial grades or laboratory formulationsof.the dye are also satisfaCtory.

CH. HAR. lab. 3b.11.77

11

2 Prepare the'indicator in dry powderform by grinding together 0.5,g of thedye and 100 g of NaCI. .

D Standard Calcium Carbonate, CaCO3:. .

Weigh 1.000 g of anhydr,s, primary istandard grade CaCO, and transfer it to .a 500 mtErlenmeyeellask. Add 1:1 licr

(equal volumes of conc. HCl and water)dropwise and with swirling of the flaskuntil the CaCO, has dissolve.). 'Bringthe volume of liquid to about 200 ml with

- water, boil a feW seconds to dispel CO,,,'cool, and add a few drops of methyl reaindicator. Adjust the color of the solutionto an intermediate orange by the dropwiseaddition of 1:1 HCI or 1:4 NH OHA1 volumeo! cOnc. NI-ICIH + A volumes If water).Transfer th2 solution quantitativdly to aone liter volumetric flask and dilute to themarls with water. (1.0 ml 1.0 miCaCO3)

E Na3EDTA2H 20 (0.01 M):

Dissolve '3.723 g of the dry reagent grade I.Na,EDTA2H.,0 in distilled water anddiltite to 1.11ter. 1.0 ml of the 0.01 Msolution 1.0 trig of CaCO3. Check theconcentration of this solutfOn by titration .

against the standard calcium carbonate o'

solution as described in II below..I

II STANDARDIZATION OF THE Na2EDTA

2H70:

A. Dilute 25.0 ml of CaCO siandard to about50 ml with distilled atar in a 125 mlErlenmeyer flask gainst a white background.

B Add 1-2 ml of the buffer solution and checkthe pH to ensure t at it is 10.0+0. I. .

^C Add approximately 0.,2 g of the indicator..

.D Add the Na ,EDTA2H,0 sloWly and withstirring until the col* changes from arose to a blue color. The color changeis more easily seen ifdhe titration iscarried out in daylight, or under a day-light fluorescent lamp. If the colorchange is not sharp, repeat the deter-mination using the inhibitor. If theendpoint is still not sharp, prepare,afresh supply of indicator:

E The titration should take less than 5 minutes,measured from the time of buffer addition.

. 19-1

Laboratory Procedure for Total Hardness

. FII

In sr. Lnalysis of this type it is advane.t-acous to carry out a preliminary, rapidtl...:.tion in"order to determine approxi-mately how much titrant will be required.This is accomplished by adding theNa9EDTA4,21-120 at a fast dropwise rateuntil the color change is observea.

PROCEDURE

1116e.Repiat steps II A through II F using sampleplace of CaCO3 standard. The amount of

sample taken should require less than 15 rn1.----of N a

2EDTA2H 20 titrant.1

IV

A

REFERENCES

1 Standard Methods for the Examinationof Water and Wastewater. 14th Edition,A PHA -AWWA-WPCF, 1976.

2 ASTM Standards, Part 31, Water;1975.

3

CALCULATION

Standardization of the Na2EDTA2H 0;

ml of CaCO equal to 1.0 ml of the Nti2EDTA2H20,3

ml.of CaCO313

Methods for Chemical Analysis ofWater and Wastes. 1974, EnvironmentalProtection Agency, EMSL, Cine'nnati,Ohio.

ml ol-Na2E11TA 2H30 required for titration

13 Total Hillikness

x 1000Hardness as mg CaCO3/1 A x'13rn, sample

A = ml of Na2EDTA2H20 for titration of sample

13= the value Obtained 4bove.

19-2

, ,

This outline was prepared by C. R.Feldmann, Chemist, National Training andOperational Technology Center, MOTSOWPO USEPA Cincinnati. Ohio 451268

Descriptors: Calcium, Calcium Carbonate:Chemical Analysis, Hardness.' Laboratory .

Tests. MagnesiuM, Water Analysis, Calcium ,Compounds, Analytical Techniqbes

113

IiAN1PERON ETRIC DETERMINATION OF TOTAL RESIDUAL CHLORINE

(BACRTITRATION FOR WASTEWATER SAMPLES)

I SCOPE A APPLICATION

A This method is'for the determination oftotal chlorine residual in domestic waste-water samples.

B It is applicable for concentrations of1 tp 10 mg Cl/liter. This range can beeictendedby dilution of the sample.'

II APPARATUS,

C Sensitizing Elegtrode and Agitator

TV apparatus can lose its sefisitivityto Aoctine. In this Case. the pointer willnot comb on scale even when the adjustingknob is turned completely clockwise. Usethe following steps to restore sensitivity.

End-point detection apparatus colligating eof a cell unit connected to a mieroarpmeter,with the necessary electricalascessories.

1 Metal electrodes must be,cleanedoccasionally with a suitable abrasive.

2 The salt.bridge must not tie pluggedwith deposits.

3 Some undissolved salt should be inthe reference electrode solution toensure constant (Saturated) composition.Fill the chamber about 2/3 full andadd enough water to cover thetablets. Then plug the cell unit intothe titrator and allow to stand for 24hours immersed in about 200 ml ofwater or sample to establish equtlibrittmof the reference electrode.

4 When moat of the tablets are used up,wall out the cell, clean the metalelectrodes and refill the chamberas above:

5 When not in use, either store thecell immersed in 200 ml water orsample solution, or else removeall electrolyte and store it dry.

B Agitator .

This part of the apparatus provides rapidand thorough mixing of the titrant antestmaterials, and also'produces a continuousflow of the 'mixtdreepast the'efectrode.

CH. A. CL. 1. 11.77

Put about 150 ml of water'containing1 to 2 mg/liter fire available chlorineinto the sample cup.

2 place the cup on the assembly, Immersingthe electrodes and agitator.

3 Add potassium iodide Crystals to the3 same water.

4 Turn on the agitator for about 3 minutes.

5 Then allow the electrodes and agitatorto remain immersed for about 15 minutee: .

6 Rinse them thoroughly with chlorine-demand-free water or the sample tobe tested.

D Conditioning the sample Cup

1 Fill glass sample cups with water containingat least 10 mg/liter residual chlorine.

2 Let stand for three hours 'or more.

3 Rinse thoroughly with chlorine-demand-,free water.

Ill REAGENTS

A 0.0282 Ndodfne Titrant

This solution can be purchased, but its concen-tration should be checked and, if necessary,adjusted to 0.0282 N. Ibtherwise, change thecalculation formula

To prepare it. consult reference I for detailsof the following:

20-1

Amperornetric Determination of Total Residual Chlorine (Back-Titration for Wastewater Samples)

.

I Prepare 0.IN arsinite solution. Thissolution is very TOXIC. Avoid ingestion.

2 Prepare 0. IN iodine solution. standard-izing it with 0. INarsenite solution.

3 Prcpare 0. 0282N iodine titrant by dilutingthe correct amount of 0. lk iodine solution.Stork it-in amber bottllis or in the dark,and Protect it from direct sunlight at alltimes. Avoid its contact with rubber.Even with precautions this solution needsa normality cher with 0. l arseditesolution each day use. See reference 1for details.

D

E

4 NOTE. This solution has two uses. It is ,INrusecrto standardize phenylarstne oxidesolution and it is used as a titrant'in testsconducted with either phenylarslne oxideor sodium thiosulfate solutions. If sodiumthiosulfate solution is to be used in the teat, Aan alternative titrant is 0. 00564N iodate

. solution. It is made with primary standardgrade potassium iodate. Reference I haspreparation details.

a If you choolie to use iodate titrant.prepare 100 ml In, phosphoric acid

%solution.lt'

B Starch Indicator Solution

This solution is used to standardize phenyl-arsine oxide solution. It is also used fortests conducted with iodate titrant. ,

See reference 1 for preparation details.

C 0.00584N Phenylarsine'Oxide (PAO)Solution

ml mg/l'available.chlorine in a 200 mlsample. This solution can le purchased.

To prepare it consult reference 1 for detailsof the following:

I Prepare approximately 0.00564N PAOsolution.

2 Adjust to final normality using results offitrating 0. 0282N iodine titrant (f.tarchindicator).

3 This PAO solution is very stable. It isalso veryTOXIC. Avo,i,d ingestion.

20-2

, B

4 NOTE: Alternatively. referehce I hasdetails for preparing and standardizing0. IN sodium thiosulfate solution, agingit, ffien diluting it to a 0:00564N solution.This solution is unstable. It requirespreservatives and daily standardization.

Potassium Iodide Crystals

Atetate Buffer Solution. pH 4.0

solution can be purchased.

COntult reference nor preparation details.

PROCEDURE

These steps utilize 0.00564N phenylarstneoxide and 0.0282N iodine titrant.

Titrator

I. Plug the titrator into a source of'115volt current.

2 Check that-the cell co -stains saturatedelectrolyte solution according to I1A above.

3 If necessary. sensitize the electrodesand agitator according to IIC above.

4 If necessary. coalition the sample cupaccording to IID above. . .

Preparation of Teat Mixture

I If the sample dip lain place on thetitrator. remove it. Empty any contentsand, Arlin thoroughly.

2 Pour sample into the cup up to the 200 mlline.

. 3 Use a pipet to add 5.0 ml 0.00564NpheOlarsine oxide (PAO) solution tothe sample. (If 5-10 mg Cl /liter isinvolved, add 10.0 ml of the PAO).

4 Add about 1 gram potassium iodide crystals.

5 Add pH4 acetate buffer solutibn to reducepH to 3.5 -4.2. Usually 4m1 is sufficient.

Amperometric Determination of Total Resiooal Chlorine (Rack- Titration for Wastewater Samples)

04

6 PI 3re the cup on the titrator with-the top edge behind the cup guidepost and with the bottom restingon the support provided.

7 Turn the switch to start the agitator.

Titration

I Rotate the adjusting knob so thatthe meepammeter pointer readsabout 20 bn the scale. (The reasonis to have a reference point).

Use a 1 11.1 pipet graduated in tenths .to adil 0.0282N iodine titrant In smallincrements. (Ncite Do not use thepipetting agaratus incorporated inthe Plastic componentsmay react with the iodine solution arkichange its strength).

During the achlition of iodine, thepointer will remain practically stationaryuntil she end point is near. At thattime, each small addition of iodinerousts a temporary to theright, then the painter retu ns to the'original position.

When a small addition of iodine causesa permanent declictibn of the pointer tothe right. you have reachedthe end point.

'1 Rerord the volume of iodine solutionused to reach the end-point.

4 Unless the sample contains alum, leaveit In the cup to heap the electrode assemblyin readiness for other tests. If alum ispresent. use distiller. water for storage.

V CALCULATIONS

A Formula,

mg/I CI IA-513)X200

A = ml 0.00564N phenyl- ,ins Oxide solution13= ml 0:0282Niodine titi,ntC = ml sample

References

I Standard Methods for the Examinationof Water and WCastewater, 14th edition.1976. APFIA-AWINA-WPCF. 1015 18thStreet, N. W.. Washington. D.C., 20036.p. '318,

This outline was prepared by Audrey D. Kroner.'Chemist. National Training and Technology

Center. MOTD, OWPO, USEPA, Cincinnati.Ohio 45268

Descriptors: Analytical Techniques. ChemicalAnalysis. Chlorine. Laboratory Tests. WaterAnalysis

1 '123-3

I,SE OF A SPECTROPHOTOMETERas

I SCOPE AND APPLICATION

A Colorimetry

If

Nlany water quality tests depend on ntreating a series of calibration standardsolutions which contain known concentra-'Hone of a constituent of interest. and alsothe sample(s) with reagents to produce acolored solution. The greater the concen-tration of the constituent, the more intensewill be the resulting color. A spectrophotometer is used to measure the amountof light of approplpste wavelength which isabsorbed ty equal "thicknesses" of diesolutions. Results from the.standardsare used to construct a calibration (standard)curve. Then the absorbance value for thesample is located on the curve to cldtermine -

the corresponding concentration.

the light path length in theavailable spectropho'ameterlbecause it is inversely relatedto the usable cOnCentraticts inthe test. (Longer path lengthsdetect lower.concentrations).

3 NOTE: Fo,r National Pollutant- -7 Discharge Elimination System

(permit),or for Drinkinip:WaterRegulations test requirements.check with the issuing / reportagency before usinglight paths(cells) that differ from the lengthspecified in the approved method.If you have permission to use analternate path length. conpentra-tions for the test can be adjustedaccordingly. These aSjustmenteare discussed in IV and MN II (below).

H Lambert Beer Law

States the applicable relationships:

A= ebc

1 A = absorbance

2 e = molar'abiorptivity

3 b light path in cm:

4 c = concentration in moles /liter

A PPARATI:S

A Requirements

Are given ae part of the method write-up

I The applicable wavelength isspecified. The unit used innanometere (nml.

2 The light path (cell dimension)is often open-ended. e. "onecm or longer." One must know

C TN. sp. 1. 11. 77

PREPARATION OF THE SPECRO-PHOTOMETER

A Phototube/ Filter

I Ma- have to choose a phototube foruse above or below a particularwavelength.

2 A filter may be required.

3 If 'the available instrument involvesa choicd. check that the phototube(and filter. if applicable.) requiredfor the wavelength to be used is inthe instrument.

4 Always handle ind wipe off thephototube and/or filter with tissueto avoid leaving fingerprints.

B Cell compartment

1 This area must be kept clean anddry at all times.

2T-1

LSE OF A SPECTROPHOTOMETER

C Cells

A set must "match" each otherin optical properties. To check.this, use the same solution atthe same wavelength, ard verilythat the absorbance value is theSame for each cell.

2 Alternatively, a single cell canbe used if It is thoroughly rinsedafter each reading.

3 Instrument cells should be freeof scratches and scrupulouslyclean.

a Use detergents. organicsolvents or 1:1 nitric acid-water.

b Caustic cleaning compoundsmight etch the cells.

c 'Dichromate solutions arenot recommended becauseof adsoiptiod possibilities.

d Rinse with tap, then distilledwater.

e A final rinsing and drying v4thalcohol or acetone before 'sstorage is a preferred practic

. iD Warm-Up 3

1 Plug in the power cord.

2 Turn the power switch on and giveft an additional half-turn to keepthe needle from "pegging."

3 Wait to use until the recommendedwarm-up time has passed. Any-where from 10 to 30 minutes maybe required. -

. .

4 If the instrument drifts duringzeroing, allow a longer time.

21-2

12J

E Wavelength Alignment

An excellent point is the krlDwil. maximum. absorption for a dilute solution of potassium

permanganate which has a dual peak ut526 nm and 546 nm. Use 2 matched cells for thefollowing steps:I Prepare a dilute solution of

potassium permanganate (about10 mg/1).

2 Follow the steps in VI A. ZeroingOperation. using a wavelength of510 nm, and distilled water as a"reagent blank." Keep the water In the cellduring this entire procedure.

3 Rinse the matched cell two timesWith tap water, then two times withthe permanganate solution.

. 4 Fill the cell three-fourths fullwith the permanganate solution. Keep thepermanganate solution in this cell duringentire procedure.

5 Thorqughly wipe the cell witha tissue. Hold the cell by thetop edges.

.6 Open the cover and gently insertthe cell, aligning it to the ridge'as before.

7 Close the cover.

8 Record the wavelength and theabsorbance reading on a sheet ofpaper.

9 Remove the cell of permanganatesolution and close the cover.

10 Set the wavelength control at thenext graduation (+5nm).

II 'If the needle Is not at infinite(symbol en) absorbance, use theleft knob to re-set it.

12 Insert the cell containing distilledwater using the techniques noted in5, 6 and 7 above.

13 If necessary. use the right knobto re-set the needle at zero absorbance.

14 Remove the cell and Insert the cellof permanganate solution using thetechniques noted in 5, 6 and 7 above.

("'

O

15 Rei ord.tn, wavelengto :in,: tneabsorbance reading.

.16 Repeat steps 9 through 15 aboveuntil absorbancereadinge arerecorded at 5 nm incremtntsfrom 510 nor through 560 nrn.

17 \lake a graph plotting absorbancerdadings against wavelengthsWith Very good resolution, therewill lo"..iwo peaks - one at 525 nn,and one at 545 nm. A single flattopped "peak" between these twowaveleritns>es acceptable.

Fx If the maximum absorbancesipeak(sioccur below or above 526 nm or546 nm. and at a number of scaleunits different from the-statedinstrument aricurac:t. the wavelengthcontrol is misaligned, To.compensatefor this until'theinstrtiment can beserviced, add or subtract tits errorscale units when setting wavelengthsfor subsequent tests,

IV CA BRATIONSTAND;HUS

A Requirements. .

A set of alibration standards is required,with concentrations usable in the availablespectrophotometer cell Hit; t path length).

1 The method reference may providea table of light path lengths andthe corresponclingapplic4ble con-centration range for oalibxtionstandards, so one can choose therange required for his instrumentcell or sample concentration.

2' The method reference maydirections for preparing one rangeof concentrations for agiven lightpath length. your cell provicle;a different length, your concentrationrequirements can be easily calculatedby recalling that the light path lengthis inversely related to concentration.Thus, if your cell is twice the givenpath length. you need the given con-centrations divided by two.

3 The method reference may givedirections for preparing only onerange of concentrations for thecalibration standari:s, and thennot be specific about the associated

ISE OF A SPECTROPHOTOMETER

1..2

path length. You will have to testif the range is applicable to yourinstrument by preparing the givenconcentrations, obtaining absorbancevalues for them and checking theresults according to section VII(below).

Preparation

The cai,,,,,tiJn standards required forspectrophotometric measurements are sodilute, that they are commonly' prepared bydiluting stronger solutions. These arc des-cribed in'general terms below.. Weights andvolumes involved in preparing these solutionsfor a specific test can be found in the methodwrite-up. 4.

StAk Solutions'

a Prepare by weighing or measuringa small amount of a chemicalcontaining the constituent ofinterest and dissolving it to aone liter volum .

h Common stock solutions haveconcentrations in the range of0.1 to 1.0 mg/ml.

c Most are refrigerated for storageand some are further treated by

,adding a preservative. Many are .

stable up to six months.

2 Stadidard Solutions

a Prepare by diluting a stocksolution (at room temperature).Common volumes are 10.0 or 20.0 mlof stock diluted to one liter.

b Resulting standardsolutiots haveconcentrations in the range of1.0 to 10.0 ugiml.

c Although some standard solutionsmay be stable for a period of time,it is a recommended practice toprepare them on the day of use.

3 Calibration (*Working: Standard Solutions

a Prepare by diluting a standardsolution. Usually a, set of cali-bration stanclard5 is requiredso that resulting concentrationsgive five to seven results withinthe sensitivity limits of the instru-ment. Common volumes are 1 to 10 mlof standard solution diluted to 100 ml.

2 1 -

FUSE OF A SPECTOPHOTOMETER

b Resulting solutions mighthave concentrations in therange of 0.01 and 1.0 ug/ml.

c A r, agent blank (distilledwater) should be includedin tele set of standards.

Adjusting Concentrations

a Ypu may find it necessaryto adjust preparation quantitiesgiven in the method write -up.because your cell (light pathlength) differs from theexample.

b These adjustments arediscussed in A Requirements(above). 'and ere usuallyapplied to the Standard(intermediate) Solution.

C Chemical Treatment

1 Most colorimetric methodsrequire that the calibrationstandards (including thereagent blank) are to betreated as the sample. Thus.they are to be processedthrough pretreatmet :ncithrough the test as if theywere samples. Then anytest effects on sample resultswill be compensated by thesame effects on results ob-tained for the treated standards.

2 One should be aware that pH isa critical condition for mostcolortmetric reactions.Ordinarily. a pH adjustmentis included in the test methodand reagents include chemicalsto control pH. Thus,the pro.ceased standards correspond to

. the samples regarding pH. andthus they correspond in degreeof color development. If stand-ards are processed in someother manner. they must bepH adjusted to correspond to

,the samples at the time of A

color development.

21-4

V SAMPLE DILUTIONS

A Concentration Limits

The concentration of the sample mustresult in an absorbance within the rangeof the calibration standards. Le., accu-rately detectible in the light path providedby the instrument. A dilution before analysisMay 6e required to accomplish this. It isnot accurate totilute a sample after pro-cessing in order to obtain a usable absorb-ance reading.

1 Record dilution volumes so a dilutionfactor can be calculated and appliedto results.

2 An analyst-often has a good estimate ofthe expected concentration of a sampleif s/he routinely tests samples fromthe same source. In this case, a singledilution, if any, is usually sufficient.

3 If a sample is from an unknown source.the analyst has several choices.

a Process the sample. If the readingshows it is too concentrated. diluteit until you get n value in the usablerange. This result is not kecurateenough to report, but you now snowhow to dilute the sample to processit through the test to get usable re-sults.

b Prepare at least a 50% dilution andanalyze it plus an-undiluted aliquot.

c Prepare a variety of dilutions.

d Use some other analytical methodto get a rough estimate of the ex-pected concentration.

B Final Volumes

1 Dilute to a filial volume sufficient to rinse'the measuring glassware and provide thetest volume cited in the referenced 'method.

2 Save any undiluted sample.

USE OF A SPECTOPHOTOMETER

-VI PROCEDURE FOR USING A SPECTRO-

PHOTOMETER

A Zeroing Operation

The foll&wing steps have been writtenfor spectrophotomete:s used in thiscourse. Check the manual for theavailable instrument for the stepsapplicable for your work.

Set the wavelength control tothe setting specified for thestandards you are testing.Approach the setting by be-ginning below the numberand dialing up to it.

2 If a cell is in the holder. re-move it.

3 Close the cell holder cover.

4 Turn the power switch/zerocontrol (left) knob until theneedle reads infinite (symbol c0 )absorbance Ion the lower scale).

5 Rinse a cell two times withtap water, two times withdistilled water. then twotimes with he reagent blanksolution.

6 Fill the cell about threefourths full with reagentblank solution.

7 Thoroughly wipe the outsideof the cell with a tissue toremove fingerprint and anyspilled solution. Ho \d thecell by the top edges.

9 Open the cell holder coer andgently slide the cell down intothe sample holder.

4 Slowly rotate the cell untilthe white vertical line onthe cell is in line with theridge on the edge of thesample holder.

12..J

10 Close the cover and turn the lightcontrol (right) knob until the needlereads zero absorbance (on thelower scale).

11

12

Record an absorbance of zero forthis zero concentration solution on.a data sheet. (See next page).

Slowly remove the cell and close thecover. (No solution should spill insidethe instrument). Keep the volution inthe cell.

13 The needle should return to the infiniteabsorbance setting. It it does not:

a Reset the needle to the co absorbancemark using the power switch/zero(left) control knob.

-b Re-test the reagent blank solutionusing steps 7 through 12 above.

c If the needle does not return to theco absorbance mark another settingas noted in a. and b. IS required.AdditionaLwarm-up time may benecessary before these settings canbe made.

B Reading Absorbances

Using a single cell in the spectrophotometersused in this course

1 piscard any solution in the cell.

2 Rinse the cell two times with tap water.and two times with distilled water. Thehrinse it two times with the lowest concen-tration standard remaining to be tested.

or with processe.1 sample.

3 Filf.the cell rbeit three-fourt- s full withthe same Standard or sample.

4 Use a tissue to remove any fingerprintsfrom the cell and any droplets on theoutside. Hold the cell by the top edges.

5 Open the yell holder cover and gentlyslide the cell down into the sample holder.

21-5

USE OF A SPECTROPHOTOMETER

8 Slowly rotate the cell until thewhite vertical line on the cellis in line with the ridge op theedge of the sample holder.

7 Close the cover.

8 Record the concentration oft he standard and its absorbance_on a data sheet. (For a sample;record its identification code andits absorbance on the data sheet).

DATA SHEET.

Concentrationmg/liter

Absorbance

fl.,00

SAMPLE

(SAMPLE

21-6

Repeat steps through 8 (above) foreach standard and sample to betested. If a large number of meas-urements are to be made, check the'instrument calibration every fifthreading.

a Use another aliquot of asolution already tested tosee if the same reading is 'obtained. If not, repeat thezeroing operation inA (above).

b Alternatively. you canlise theblank, if supply permits. andrepeat the zeroing operationin A. (above).

10 When all the readings have beenobtained, discard any solutionremaining in the cell and rinsethe cell with tap water, Cleanthe cell more thoroughly. (III C.3).as soon as possible.

11 If no other tests are to be done.turn off the instrument. pull out

the plug and replace any protectivecovering.

(e*CHECKING RESULTSVII

A Readings Greater Than 0.70.

On our instrument. these are consideredto be inaccurate. Check the manual foryour instriiment or check the scale divi-sions to determine the limit for othermodels.

1 Do not use readings greater than0.70 to develop a calibration curve.

2 From five to eight points (countingzero) are recommended for constructinga calibration curve. If you have fewerthan five usable values, you shquld not -;draw curve.

3 To prevent excessively high values, in hlture tests, decrease the cellpath length. if possible, by usingan adapter and smaller cell.

4 If you cannot decrease the dell pathlength, you can at least obtainenough values to construct a curve.Prepare standards with five to eightconcentrations ranging from zero tothe cotkentration of the standardhaving an absorbance nearest to'0.70.This gives you more values for a curve,but it reduces the applicable range ofthe test. Usually the sample can bediluted before testing so the miltwill fit on the standard curve.

13 Highest Reading is Less Than 0.6

1 Increase the cell path length by usinga larger cell.' A higher reading'results.

2 Prepare a different Set of standardswith greater concentrations.

VIII CONSTRUCTING A CALIBRATIONCURV.E


If you have from'five to eight usableabsorbance values. yoq.can constructa concentration curve,

A Graph Paper

Should be dividel into squares ofequal size in both directions

13 Concentration Axis

1 Labeling

The longer side should belabeled at equal intervalswith the concentrations ofthe calibration standardsmarked from 0.0 to at leastthe highest concentrationrecorded for the standardson the data sheet.

2 Units

a It is most Convenientto express these con-centrations in the unitsto be reported. Otherwise.a uniteconversion factorwould have to be appliedto obtain final. reportable-values every time you usethe curve.

Example: If you dilute astandard solution to make100.0 ml volumes of cali-bration standards, you -have a choice in .expressingthe resulting concentrations.You can use weight/ 100 ml.or you can calculate weight/I liter. If you are to reportresults as weight/liter. butyou construct yOur curseusing weight/ 100 ml, you willhave to multiply every sampleresult from the curve by1000 Or 10 to obtain the re-pffiable value. It is mucheasier to convert the originalcalibration standard concentra-tions to the desired units and touse these as labels on the graph.

C Absorbance Axis

1 Labeling

The shorter sid should belabeled at equal tervalswith absorbance mberemarked from 0.00 at least0.70 absorbance units.

-13 Plotting the Curve

Use the absorbances recordedfor each standard concentrationto plot points for the.curve.

2 The points should fall in areasonably straight line.

3 Use a straight-edge to-draw 'a line of best fit thrpugh thepoints. If the points do notall fall on the line, an acceptableresult is an equal number ofpoints falling closely above.as well as below the line.Experience provides a basisfor judging acceptability.

4 It is not perfnissable to extra-polate the curve.

IX USING THE CALIBRATION CURVE

A Finding concentration of the sample

I Use the absorbance value(s)recorded for the sample(s), andthe calibration curve to find theconcentration(s). If the Eoncentra-tton units differ from those requiredfor reporting results, apply a unit

,conversion factor (3/111B. 21.

2 If more than one dilution Of a samplewas tested, use the result'that fallsnearest the middle of the.curve.

13 If a sample was dilated, calculate thedilution factor and apply it th.the con-centration you find forthe sample fromthe calibration curve.

12321-7


1 Di .on Factor=This outline was prepared by'Audrey D.

final.dilution volume Kroner. Chemist. National Training andml smple used in dilution Operational Technology Center. MOTD.

OWPO. USEPA. Cincinnati, Ohio 452682 Example- You diluted 10 ml

sample to 50 ml. The con-centration found by using acalibration curve was 0.5 Descriptors: Analytical Techniques.mg/liter. Chemical Analysis. Colorimetry,

Laboratory Tests. SpectrophotometryThen

constituent. -mg/I

21-8

50m1 x 0.5 mg10 ml liter

= 2.5 mg/liter

123

LABORATORY PROCEDURE FOR TOTAL PHOSPHORUS

1 SCOPE AND APPLICATION

A This method 4 for the determination oftotal ptuseptiorus in drinking, surfaceadd saline waters and in domestic andindustrial wastes.

B It is applicable for concentrations of.0.01 to 1.0 mg Pinter. This range canbe extended by dilution of the sample.

II APPARATUS

A Spectrophotometer with a light path of1 cm or longer for measurements at 850or 880 run :

B pH meter and electrode(*) to fit 125 nilErlenmeyer Reek

C Filtration assemblies for 0.45 i.m discs.to filter about 10 ml test solution

11 PREPARATION OF GLASSWARE (1)

A Traces of phosphorus on the glasswareused in the test will cause significanterrors. The glassware and filtrationapparent' should be acid-washed. Ifthis equipmentcan be reserved to useonly for this test, the acid wash is onlyrequired'occesionally. .

I Wash equipment with hot 1:1 HC1in a hood. Wear rubber gloves.

2 Rinse with tap water, then distilledwater.

3 Fill.or rinse each piece with thecombined reagent used in the testto check for traces of phosphorus.A blue color will form if 'phosphorusis present.

4 Repeat the washing instructions untilall phosphorus is removed (no color):

5 Then rinse everything several times,with dattilled water and allow it to dry.

CH. PHOS. lab. 4: 11.77

IV PREPARATION OF FILTER DISCS

The 0.45 um filter discs must be phosphorus-free. These can be ptirchased or you cantreat &see as follows- 2)

A Soak the discs in distilled water, about 2liters for every 50 discs. for 1 hour.

B Pour off the water and-replace it.

C Soak the discs another 3 hours.

D Pour off water and dry.

E Check t..) or three dried discs by placing themin a small volume of combined reagent. If ablue color develops..phosphorus is presentand you should repeat the wash operations.If no color develops, the discs are readyfor use.

REAGENTS11)

A ION Sodium HydroXide

Dissolve 40 grams sodium hydroxide, in about80 ml distilled water. Caution: heat and fumesare liberated. Cool and dilute to 100 rill.'

- B 0.IN Sodium Hydroxide

Dilute 1 ml ION sodium hydroxide to 100 ml.

C 11N SulluriC Acid

Slowly add 310 ml conc. sulfuric acita to GOO mldistilled water. When cool, dilute to one liter.

D 0.11N Sulfuric Acid

Dilute 1 ml 1IN sulfuric acid to 100 ml.

E 5N Sulfuric Acid

Slowly add 70 ml conc. sulfuric acid to 400 mldistilled water. Caution: Heat is liberated.When cool, dilute to 500 nll.

13[1 22-1

LABORATORY PROCEDURES FOR TOTAL PHOSPHORUS

F Antimony Potassium Tartrate Solution

Weigh 1.3715 g K(SbO)C4H406. 1/2 H2O.Dissol;:e in 400 ml distilled water in a 500nil volumetric flask and dilute to volume.Store at 4°C in iLdark, glass-stopperedbottle. .

G Ananoniuni Molybdate Solution

Dissolve 20 g(NH4)63.1o7024 4H20 in 500ml of distilled water. Store in a plasticbottle at 4°C.

II 0. 1M Ascorbic Acid

Dissolve 1.76 g of ascorbic acid in 100 mlof distilled water. The solution is stable forabout a week if stored at 4°C.

1 Combined Reagent

This reagent must be freshly prepared foreach run. For 100 mr, mix E. F. G. and H.in the following proportions and order. (Allreagents must be at room temperature)

1 50 ml 5N sulfuric acid.

2 5 ml antimony potassium tartrate solu-tion. Mix well. If 'turbidity forms; letmix stand a few minutes. then shakeagain. Repeat until turbidity disappears.

3 15 ml ammonium molybdate solution.Mix well. Follow directions in 2. ifturbidity forms.

4 30 ml 0. IM ascorbic acid. Mix well.Follow directions in 2. if turbidity forms.

.1 AmmoniuM Persulfate,

No preparation is required. This is avigorous oxidizing agent so store it withappropriate caution.

K Stock Phosphorus Solution

Weigh 0.2197 grams of potassium dihydrogenphosphate. 1(112Pbe which has been driedat 105°C and cooled. Dilute to I liter in avolumetric flask. This solution is stableup to 6 months if stored at 4°C.

1.0 m' =0.05 mgP.

22-2

L Standard Phosphoous Solution

I This solution should be prepared ankletime of use. It is for tests utilizing 1 cmspectrophotometer cells. For other lightpath lengths, adjust the concentrationaccordingly.

2 Dilute 20.0 ml stock phosphorus solution(at room temperaturr.% ;DI liter in avolumetric nabt.

3 1.0 ml= 1.0igP.

VI PROCEDURE(')

A Preparation of Calibration Standards

1 Mark nine 50 ml volumetric flasks withthe concentrations listed in Table 1.

2 Using volumetric pipets. measure theamounts of standard phosphorus solutionlisted in the table into the corresponding50 ml flask.

TABLE 1

Use These -mls St'd P4sop 50 ml

Por thisConc., mgPil

Absorhances.

0 0.001.0 0.023.0 0.06S. U 0.10

10.0 0.2020.0 0.4030.0 0.60 .

40.0 0.8050.0 1.00SAMPLE

IJI


3 Dilute each to the 50.0 ml mark.stopper and mix thoroughly.

4 Note: The flask containing 50 mldistilled water (0.00 mgP) is thereagent blank. .

5 Mark nine 125 ml Erlenmeyerflasks with the concentrationslisted in Table 1.

it6 Pour the n e standards into thecorrespiin g Erlenmeyer flask.

B Measurement of Sample

1 Label a 125 ml Erlenmeyer flaskwith the sample identification code.

2 Shake the sample.

3 Immediately pipet 50 ml of sampleinto the flask. .

a If the P concentration of thesample is unknown or if itis known to be greater thaii1.0 mg/l, use the well shakensample to make appropriatedilutions in 50 ml'volumetricflasks.

b Record the ml of sample usedin dilution.

c Transfer the 50 mlto 125 ml Erlenmeyer flasksthat have been labeled with theml of sample used in the dilution.

C. Digestion of Calibration Standards andSample(s)

I Turn on the hot plate(s). Youneed surface area for all the125 ml Erlenmeyers flasks con-taining standards and sample.

2 Use a 10,ml graduated pipet toadd 1 ml IIN sulfuric acid toeach flask.

3 Use a measuring scoop to add0.4 gram ammonium persulfatet. each flask.

Add 4 glass boiling beads toeach flask.

5 Swirl each flask to thoroughlymix the contents.

6 Place the flasks on a hot plateand gently boil for 30-410 minutesor until a volume of about 10 mlis reached. CAUTION: Do notallow any to go to dryness.Alternately, the flasks may beauto-claved for 30 minutes at121C (15-20 psi).

7 CoO1 the flasks.

D Filtration of Standards and Sample(s)

1 Filter each digested standard andsample through individual phosphorus-free. 0.45 gm pore size filter discs.

a Be sure filter apparatus is freeof phosphorus contamination.

b Rinse each Erlenmeyer flaskwith two 5 ml portions of dis-tilled water and filter eachportion through the correspondingdisc.

2 Pour each filtrate back into its corres-ponding 125 ml Erlenmeyer flask. Useone 5-10 ml portion of distilled waterto rinselhe filtering flask into theErlenmeyer flaik.

E pH Adjustment of Standards,. and Stun ple(s)

I Adjust the pH of each solution to7+0.2, using a p11 meter as follows:

a CAUTION: Be sure any buffersolution used to calibrate themeter has been completelyflushed off the electrode(s). Usecombined reagent check.

b Add ION sodium hydroxiderapidly to a pH of 3, thendropwise to a pH of 6.

c Add 0.1 N sodium hydroxidedropwise until the pH is between6.8-7.2. If you over-shoot thedesired pH. add 0.11N sulfuriracid dropwise until the pH isbetween 6.6-7. Z,

2 Add 0.1 ml (2 drops) of 11N sulfuricacid to each pH-adjusted solution.

1" 22-3


3 Pour each solution back intothe 50 ml volumetric flaskused to prepare it. (You willneed an additional 50 ml flaskfOr any undiluted sample(s). )

4. If there is leas than about 45 mlin the volumetric flask, use about4 ml distilled water to rinse each125 ml Erlenmeyer into the 50 mlvolumetric flask.

5. each solution to the 50.0ml mark, ,

6 Stopper and invert each flaskto thoroughly mix the contents.

7 Return each solution to itscorreeponcling-(qlean) 125 ml

. Erlenmeyer flask.

F Colorimetry

1' Pipet 8:0 ml of combined reagentinto each Erlenmeyer flask.

2 Gently swirl each flask.

3 Note the time. cter 10minutes (and not snore than30 minutes), make spectra-photometric readings at880 rim. (650 nm may also ,be used).

a Use the 0.00 mgP/literreagint blank to calibratethe instrument.

b Record the abeorbances inTable 1 (A.2. above) nextto the corresponding con-centrations of the standards.A space is also providedfor recording the absorbanceof the sample.

VII CALIBRATION CURVE

A Obtain a piece of graph paper and labelthe axes. The longer aide should belabeled with the concentrations of thestandards as given in Table 1. Thishorter axis is labeled from 0,00 to1.00 as the absorbance axis.

22-4

B Use the absorbances recorded for-thestandards in Table 1 and the corres-ponding toncentration of the standardsto plot 'a calibration cur ve.

VIII RESULTS

A Use the absorbance value recorded inTable 1 for the sample to find tbe totalphosphorus concentration fronithe curve.

so 1 If more than one dilution was run.use the result that falls nearest the ,middle of the curve.

133

B Dilution Factor

If the sample was diluted. calculate .

the dilution factor and apply it to theconcentration you found for the sampleby using the curve.

I Dilution Factor =50 ml

ml sample used in dilution

2 Example: You diluted 10 ml sample 'to 50 ml. The concentration foundusing the curve was 0.4 mg/1. Them

Total P. mg/1 = 50 ml x 0.4 mg /110 ml

Total P. mg/1 = 2.0

REFERENCES

1 Methods for Chemical Analysis ofWater and Wastes. 1974. U. S. EPA,MDQARL, Cincinnati, OH. 45268.

2 Standard Methods for the Examinationof Water and Wastewater. 14th ciition,1976. APHA-AWWA-WPCF, Washington.D. C.. 20036.

This outline was prepared by Audrey D. Kroner,Chemist. National Training and OperationalTechnology Center. MOTD. OWPO, USEPA,Cincinnati, Ohio 45268

Descriptors: Analytical Techniques. ChemicalAnalysis, Laboratory Teets, Nutrients.Phosphorus. Water Analysis

.FIXOBIDE ANALYTICAL PROCEDURES SPA DNS

I 6PADNS PHOTOMETRIC METHOD

A fleageks

1 Ebssolve 0.958 g. S,PADNS in distilledwater and dilute to approximately 300 .ml in a 1-jiter volumetric flask.

2 Dissolv0.133 g zirconyl chloride inabout 200 ml distilled water and. add tothe. flask.

3 Add 350 ml concentrated HC1 and diluteto I liter.

4 Fluoride stock solution: 0.2210 g NaFdissolved in 1 liter distilled water(1 ml 0.1 mg F):

5 Standard fluoride solution: dilute abovestock solution 1:10 with distilled water(1 ml 0.01 mg F) (or dilute 1:104 tomake 1.0 ppm F standard).

6 Sodium arsenite s ution: 5.0 gNaAs 02 dissolved 1 liter distilledwater.

B Procedure

1 Prepare two separate standards asfollows:

a 0 ppm standhrd - carefully measure(with a volumetric pipet) 50 ml ofdistilled water.

b 1.0 ppm standard - carefully measure.-(with a volumetric pipet)50 ml

1.0 ppm F standard solution.

2 Carefully measure 50-ml portions ofeach unknown sample.

3 Add 10 ml of reagent to each standardand sample.

4 Carefully shake each of the standards and, sample(s).to mix them with reagent.

134CH. HAL. f. lab. 35.11,77

5 With the distilled-water standard (0 ppmF) in the cuvette, adjust the photometerslit so that a reading of .300 or .500 onthe 'mance scale is obtained. Usea wa Lgin of 570.

Replace the 0 ppm standard'with the -

other standa'rd and samples in succes-sion, noting the abso. .ante reading Ineach case.

7 Calculate the fluoride content of theunknown samples by the formula:

XA - Axx

A0 - Al

where X is the fluoride content of thesample in ppm,

where Ao is the absorbance 'readingof the 0 ppm standard,

where Ax is the abs4rbance readingof the unknown sample, and

where A1 is the absorbance readingof the 1.0 ppm standard.

If preferred, a curve may be drawn byplotting the absorbance readings of thetwo standards and connecting with astraight line. The Um may be extendedto 1.4 ppm, bbt no further.

Reference

1 Standard Methods for the Examinationof Water and Wastewater, 14th ed...1978, APHAAWWA-WPCF,Washington, p0388

Thig outline was prepared by Dr, E.Bellack. Office of Water Supply, EPA:.Washington. D. C.

Descriptors: Analysis, Chemical Analysis,Fluoridation. Fluorides. Fluorine, WaterAnalysis.

23-1

FLUORIDE ANALYTICAL PROCEDURES - ELECTRODE

ELECTRODE METHOD(Using a pH Meter)Standard So in.Reagents

I TISAB: "

a Place approximately 500 ml distllledwater in a I-liter beaker. Add 57 mlconc. acetic acid, 58 g. sodiumchloride and 12 g. sodium citrate.Stir to dissolve.

b PlaCe the bealter in water bath (forcooling), iniert a calibrated pHelectrode and a reference electrodeinto the solution and slowly addapproximately 6N sodium hydroxideuntil the pH is between 5.Q and 5.5.Put into a 1-liter volumetric flaskand add distilled, water to the mark.Mix well.

Fluorite stock solutiorr

a Dissolve 0.2210 g. sodium fluoridein1 liter of distilled water (1 ml = r0.1 mg F)._

3 Standard fluoride Liona Dilute 20 ml of the aboYe stock

solution to 1 liter (1 ml 0.002 mg F).

B Procedure.

1. Prepare 5 settee of standards byOpening the indicated amounts ofstandard fluoride solution into labeled150-m1 beakers, adding the indicatedamounts of distilled water (by pipet),and then adding 50 ml of TISAB to each.

, .pt. HAL. r. lab., 2, 11.77

mlDist. Water mg F ppm F

5 45 0.01 0.210 40 0. 02. 0.415 35 0.03 0.520 30 0.04 0.25 25 0.05 1. 050 0 p c0.10 2.0

2 In 150-m1 beakers place by'pipet 5 ,m1samples. Add 50 ml of TISAB to ch.Bring standards and samples to thsame temperature.(plus or minus

3 Immerse the electrodes and measure thedeveloped potential while stirring thetest solutions with a magnetic stirrer.Allow he electrodes to remain in thesolution for.,p minutes before takinga final my reading. Rinse electrodeswith distilled water and blot dry betweeneach reading. Record my reading foreach standard.. . .

4 Read samples similarly. Confirm theelectrode calibration by checking thereading of the 1 .0 ppm Standard be-tween samples.

5 Plot the potential measurement ofstandards in my along the arithmetichorizontal axis of 2-cycle semi-logarithmic graph paper. Plot ppmon the vertical logarithmic axis,. start-ing with 0.1 ppm at the bottom.

6,i Read the fluoride,c1Mcentration of theunknown samples from the standard

, curve prepared from the readingsobtained on the standards.

24 -1,

Fluoride 'Analytical Procedures - Electrode

Il El.F.CTRODE METHOD USING PORTABLEMETER (Specific Ion Meter)

A Reagents

1 TISAC

a Prepare as for regular ElectrodeMethod. or

b Use commercially prepared TISABor Fluor-Ade buffer

2 Standard fluoride solution

a Dilute fluoride stock solution 1:10with dfstilled water to make 10 ppmF standard (1 ml 0.01 mg F) anddilute fluoride sto'ik solution 1:100with distilled water to make 1-ppmF standard, or

b Use commercially prepared standards.

Procedure

I Prepare two standards.

a In a beaker labeled "1. 0 ppm" add bypipet 10 ml of the 1.0 ppm fluoridestandard solution or about 20 ml ofcommercial 1..0 ppm standard.

In a beaker labeled "10 ppm" add bypipet 10 ml of r - 10.0 ppm fluoridestandard soluton (1 ml .5 0.01 mg F)or about 20 ml of the commercial2.0 ppm standard:

2 Add 10 ml (by. pipet) of TISAB to each ofthe standards. Commercial standardsalready have TISAB adaed so require no'further treatment.

b

I

24-2

3 Pipet 10 ml of samples into labeledbeakers. Add 10 ml of TISAB to each.

4 immerse the electrodes in the 1.0 ppmstandard, Set the- selector of a MOddl.407A meter on "X'" and swirl the beakergently for 3 minutes. On the Model 409meter the selector should be set at"0.5 - 2",

5 Adjust the meter so that the pointerreads 1.0 ppm. Use the calibrationknob on a Model 407A or the "0.5 - 2"knob on a Model 409.

6 Turn off the meter. lift the electrodes.rinse them in distilled water and pat

with a tissue.-

7 immerse the electrodes In the 10 ppmor 2.ppm standard, set the selector ofa Model 407A meter on "X"'' or that of aModel 409 on "0. 1 - 10" and sad rl thebeaker gently for 3 minutes. Adjust

'the meter until, the pointer indicates theproper concentration, using theTemperature Compensator oh a Midel407A or the "0.1 - 10" len* on a Model409. Turn off the Meter, rinse and drythe electrodes after each use.

8 Immerse the electrodes In a sample, setthe meter IseleCtor to i'X'" or "0.5 - 2",swirl the beaker gently for 3 minutes.and read the fluoride concentrationdirectly.fiom the meter scale,

REFERENCE

Orion Research, Inc.. Analytical MethodsGuide. October 1971

This outline was prepared by Dr. E. Bellack.Office of Water Supply. EPA, Wsishington, D.C.

Descfiptors: Analysis, Chemical Analysis,Fluoridation, Fluoride. Fluorine. WaterAna lysis.

1 3 y'

sis.

DETERMINATION OF NITRATE/NITRITE NITROGEN (CADMIUM REDUCTION METHOD)

I SCOPE AND APPLICATION III

A This method is for the determination oftotal nitrate and nitrite nitrogen in drink-ing. surface and saline waters, domesticand industrial wastes. By carrying outthe procedure without the initial reductionstep. the method determines only nitritenitrogen. Thus separate nitrate nitrogenand nitrite nitrogen values can be obtainedby carrying out the procedure first with.and then without, the initial reduction step.

B The applicable range of this method is0.01 to 1.0 mg/liter nitrate/nitrite nitrogen.The range may be extended by dilution ofthe sample.

11 APPARATUS

A Spectrophotometer with a light path of 1 cmor longer for measurements at 540 nm.

B pH meter and electrode(s).

C Seduction Column.

1 Cut off both ends of a 100 ml volumetricpipet so that it measures 10 cm from thebase of the cu to the top, and about 25 cmfrom the of the cup to the end of thecolumn-.

2 Use glass wool as a plug for the'column.

3 Attach a piece of tygon tubing (about 7.5 cmlength)to the lower end of the column.

4 Put two screw clamps around the tygontubing. .The.upper clamp is used to adjust

,the flow .rate and the lower is used to stopthe flow of solution.

R EA G EN TS" )

A Distilled Water

An ion exchange column in conjunctionwith a still provides an adequate supplyof highly pure water.

B Concentrated Ammonium Chloride - .

EDTA Solution

Dissolve 13g ammonium-chloride and I. 7gdisodium ethylenediamine tetraacetate in900 mi distilled water. Adjust to pll 8.5with concentrated ammonium hydroxideand dilute to 1 liter with distilled water.

C Dilute Ammonium Chloride - EDTA Solution

Dilute 300 ml concentrated ammoniumchloride - EDTA Solution to 500 ml withdistilled water.

D Color Reagent

Add 100 ml concentratedphosphoric acid toabout 800 ml distilled water in a 1 liter volu-metric flask. Mix well. Dissolve lOgsulfanilamide and lg N11-napilthyl)-ethylene-diamine dihydrochloride in the acid mixture.Mix, then dilute to 1 liter with distilledwater.

E Zinc Sulfate Solution (Turbidity Removal)

Dissolve 100g zinc sulfate heptahydrate indistilled water and dilute to 1 liter.

F

5 Put the clamp in S. buret support on a ring.

G41:

6 You can purchase reduction columns forthis procedure.

CH. N. n/n, lab. 1.11.77 "'

6N Sodium Hydroxide Solution (TurbidityRemoval)

Dissolve 24g sodium hydroxide in about 80 midistilled water. Caution: Heat and fumes areliberated. Swirl to dissolve and cool the mix-ture. Dilute to 100 ml with distilled water.

Non-polar Solvent (Oil and Grease Removal),a supply of freon, chloroform or equivalent.

H conc. Ammonium Hydroxide (pH adjustment)

1

13 7

non-:. Hydrochloric Acid (pH adjustment)

25-1

DETERMINATION OF NITIIATE/NITRITE NITROGEN (CADMIUM REDUCTION mEnioD

.1 6.: Ilydr chloric Acid

Add 5u mi conc. hydrochloric acid to a',out.15 nil distilled water. Swirl, cool anddilute, to 100 nil.

Copper Sulfate Solution

Dissolve 20g copper sulfate pentahydratein 500 nil distilled water. Alute toI liter.

I. Granulated Cadmium

Each column requires about 20g cadmium.granulated to*ass a 10 mesh sieve and to heretained on a 40. then a 60 mesh sieve.Filing stick cadmium should be done in ahood to avoid inhalation of small particles.The correct mesh cadmium can be purchased.

NI Stock Nitrate Solution

Weigh out 7.218g potassium nitrate. dissolveit in distilled water and dilute to 1 liter.Preserve with ml chloroform. This solu-tion'is stable up to 6 months if stored at 4"C.

1.0 nil = 1.00 mg nitrate nitrogen

N Column-Activation Nitrate Solution

This solution shOuld be preparedAt the timeof use. It is required only when the cadmiumhas been Washed with acid and copperized toprepare or to re-activate a column.

1 Dilute 1.0 rol stock nitrate solution(at room temperature) to 1 liter ina volumetric flask.

2 1.0 ml = 0.001 mg nitrate nitrogen

0 Standard Nitrate Solution

This solution should be prepared the timeof use. It is for tests utilizing 1 cm spectro-

'photometer cells. For other light path lengths.adjust the concentration accordingly.

I Dilute 10.0 ml stock nitrate solution(at room temperature) to 1 liter.in avolumetric flask.

2 I.0 ml = 0.01 mg nitrate nitrogen.

25-2

1 3

P Stock Nitrite Solution

Weigh out 6.072g potassium nitrite.dissolve it in distilled water and uteto I liter. Preserve with 2 ml chloroform.The solution is stable up to 3 months ifstored at 4"C.

1.0 ml = 1.00 mg nitrite nitrogen.

Q Standard Nitrite SolutionThis solution should be prepared at the timeof use. It is for tests utilizing 1 cm Spectro-photometer cells. For other light path lengths.adjust the concentration accordingly.

I Dilute 13.0 ml stock nitrite solution(at room temperature) to 1 liter ina volumetric flask.

2 1.0 ml = 0.01 mg nitrite nitrogen

IV PREPARATION OF REDUCTION COLUMN( I )

A Copperizing the dadmium

I Weigh out about 20g cadmium granules)and place them in a 400m1 beaker.

2 Add enough 6N hydrochloric acid tocover the granules.

(Swirl. thendecant off the acid. (Note:All through this procedure; decant intoa filter paper in a funnel supported inan old bottle. etc.. whenever smallparticles of cadmium are part of thedecanted material. I

4 Add enough distilled water to coverthe granules.

5 Swirl tdwash. then decant off the water.,

6 Wash the granules two times more usingstcpsk and 5 above.

7 Pour about 100 ml 2% copper sulfatesolution over the granules.

8 Swirl until the blue color of the coppersulfate fades (about 5 minutes). A brown.very fine'precipitate of metallic coppershould form.

9 Decant off the capper sulfate solution.

10 .Repeat the addition of fresh copper sulfate .

c.

D TEBAIINATION OF NOFRATE/NITRITE NITROGEN (CADMIUM REDUCTION NIET1.014)

solution as in steps 7 thrJugh 9.A significant amount of the brown.copper precipitate should form(If no precipitate forms, do athird treatment using steps 7 - 9

'above).

II .Remove all the brown precipitateby adding at least 10 distilledwater rinses(in about 75 mlamounts), and decanting offthe precipitate into the filterpaper set-up described in 3above. Using a spatula tomove the precipitate along withthe water facilitates this operation.

It Checking Granule Size

I Use a spatula to transfer thecopper-cadmium granules toa 60 mesh sieve.

2 Hold the sieve over the filterpaper set-up. Squirt distilledwater over the granules atleast three times to wash any"fines" through the sieve.

3 Use the squeeze bottle fordisti:.-d water and a spatulaho return the granules to thebeaker.

4 Decantoff excess water.

C Filling the -7olumn

I Close one of the clamps onthe delivery tube of the column.

2 Slowly fill the column almostto the top of the cup with diluteammonium chloride - EDTAsolution. Release any air

-pockets that arc firmed.

3 Slowly add the copper-cadmiumgranules and allow them to "float"down through the solution.. Usea spatulao move the wet granulesout of the beaker. Continue thisaddition until you have looselyfilled the column up to about 2 cmbelow the'cup-like section. (Thecolumn of granules should be about18.5 cm in length).

D, Checking tin Floa Rate

I, Place a graduate under the columnand open the screw clamp.

2 Time the rate of flow. It shouldbe between 7 ml and 10 nil/minute.

3 If the flow rate is too fast, tightenthe screw clamp and re-check therate. Do this until the flow is 7-10ml/minute. If the clamp shuts offthe flow before. the desired rate isobtained, add moFe coppe'r-cadmiii,,granules to the column: Continuechecking the rate and adding granni....until the 7-10 nil/minute rate

. is orbit...3. DO Noi let the e.iun,"go dry. .

4 If the flew rate is too slow,, loosen the clamp and re-check

the rate. If the 7-10 nil/minuterate cannot be achieved, removesome of the granules throughthe cup end of the column andre-check the rate. DO NOTlet the column go dry.

5 When the 7-10 ml/minute flowrate 'is achieved, allow the re-maining solution to drain antilit is about 2.5 cm above thetop of the granulea. Use thesecond clamp to stop the flowof solution from the column.

6 Add about 70 ml dilute ammoniumchloride - EDTA solution to thecolumn.

7 Allow this to drain through atthe established flow rate of 7-10ml/minute. Stop the flow whenthe solution is about 2.5 cmabove the top of the granules.

8 The. column of granules shouldalways be covered with solutioR:When the column is not is use,use dilute ammonium chloride -EDTA solution to cover thegranules. (Allow extra forevapo'ration).

E Activation of the Column iI Pipet 25.0 ml of the columnactivation nitrate solution (1 ml =

0.004/mg nitrate nitrogen) i 4250 ml Erlenmeyer flask.

2 Add 75 ml dilute ammoniumchloride - EDTA solution andmix.

33j1Ilace a 250 ml beaker under the 25-3


rolunin and. At' neceesary,bring the level of storagesolution in the column downto the top of the granules.

4 Place a graduated cylinderunder the column.

5 Pour the mixture preparedin 1 and 2 (above) into thecolumn, unscrew the stop -flow clamp and time theflow rate. If the rate isnot bettleen 7-10 ml perminute, adjust the screw -clamp which. regulat?flow until the rate is achieved.,

Continue the flow of agiivatingmixture through the columnuntil the level of solution isabout 0.5 cm above the topof the granules. Stop the flow.Any collected mixture shouldbe discarded.

7 Mete re and pour into thecolu about 40 ml diluteammonium chloride - EDTAsolution. Repeat step 5 and6(above) procedures. This"washes" the column-activation nitrate solutionoff the granules. If youhad to do much adjustingto get the correct flow ratein 'die step 5 procedure,do a- second rinse with about40 ml fresh. dilute ammoniumchloride - EDTA solution.

8 The column is now readyfor use.

V REMOVAL OF INTERFERENCESFROM SAMPLES

A Turbidity

1 Filter about 200 ml samplethrough a glass fiber filteror a 0.45 pm membranefilter.

25-4 1 4 Li

2 Alternatively. add 2 mlzinc sulfate solution to200 ml sample andthoroughly mix.

3 Add 0.8-1 ml (18-20 drops) sa_sodium hydroxide solution tobring the pH to 10.5 (Use apH meter).

4 Allow the heavy. flocculentprecipitate 4o settle by lettingthe treated sample stand afew minutes.

5 Filter the supernatant througha glass fiber filter oR a 0.45 Ammembrane filter.

B Oil and Grease

1 Adjuit the pH of about 200 ml ofa non-turbid sample to 2 byaddition of conc. hydrochloricacid. (Use a pH meter).

2 Place the sample in a 500 mlseparatory funnel.

3 Add 50 ml of a non-polar solvent.such as freon or chloroform.

4 Shake gently to extract the oiland grease.

5 Allow the solvent layer to separate.

Collect the solvent layer in a 100ml beaker and discard it.

7 Repeat steps 3-8 with a fresh,50 ml portion of solvent.

8 The ):Imple.remaining in the separatoryfunnel is now ready for .testing.

VI DETERMINATION OF NITRATE PLUSNITRITE

A Preparation of Nitrate CalibrationStandards

c,

DETERMINATION OF NITRATE/NITRITE NITROGEN (CADMIUM REDUCTION METHuDi

-1 Mark six 100 ml volumetricflasks with the oncenttationalisted in Table .

2 Using Volumet ic pipets.measure the amounts ofstandard nitrate scalutionlisted in Table 1 into thecorresponding 100 mlvolumetric flask.

TABLE 1

Use these For thismls St'd NO3 conc.. mg AbsorbancesSol/100 ml NOi-N/1

0.0 ml 0.000.5 ml 0.051.0 ml 0.102.0 ml 0.205.0 ml 0.50

10.0 ml 1.00SAMPLE

3 Dilute each to the 100:0 mlmark, stopper and mixthoroughly.

4 NOtei The flask containing100 ml Distilled water(0.00 mg 14(03-N/1) is thereagent blank.

5 Mark six 150 ml beakerswith the concentrations listedin Table 1.

8 Transfer each calibrationstandard to the correspond-Mg beakgr.

B pH Adjustment of Standards and Sample

1 Transfer about 200 ml sampleto a 400 ml beaker.

a Any treatment requiredto remove interferencesshould have been completedprior to this step.

b Samples may requiredilution if the nitratenitrogen concentrationexceeds 1 mg/liter.

I41

- 1) Use a 109 ml volumetricflask and a pipet for eachdilution.

2)/Record the ml sample.used in the dilution. _

3) Transfer the diluted sampleto a 150 ml beaker.

4) Save the remainder of samplein the 400 ml beaker. It willbe required for the nitritedetermination.

2) Use a meter to check the pH of eacrisolution. Ir necessary. adjust thepH So between 5 and 9 with eitherconc. hydrochloric acid or conc.ammonium hydroxide.

C Reduction of Nitrate Nitrite inStandards and Samp plus ColorDevelopment

1 Beginning with the 0.00 mg/liternitraternitrogen standard (reagentblank). process each standardand sample through the reductioncolumn(s) using the following steps.

2 Pipet 25.0' nil of the standard orsample into a 250 ml Erlenmeyerflask labeled with the concentrationof the standard or the code of thesample.

3 Add 75 ml dilute ammonium chloride-EDTA solution to the same flask andmix wellbypirling.

4 Place a\g`raduated cylinder (at least25 ml capacity) under the column.

5 Fill the column with the mixtureprepared in 2 and 3(above).

Open the stop-flow clamp.

7 Again. check that the flow rateis 7-10 ml/minute.and make anyadjustments necessary to achievethis flow.

25-5

DETERMINATION OF NITRATE /NITRITE. NITROGEN (CADMIUM REDUCTION METHOD)

8 Use the stop flow clamp when 25 ml hasbeen 'collected. Discard this "wash".

9 Pour the rest of the mixture preparedM 2 and 3 (above) into the column.

10 Rinse'the Erlenmeyer flask and shakeout excess distilled water.

11 Place the flask under the column andcollect the rest of the mixture. Stopthe flow when the solution is about 0.5cmabove the top of the granules. The flaskcontains nitrite in solution, i.e.. anynitrite in the original sample. plus thenitrite formed by the column's reductionof nitrate in the original samples.

12 IMMEDIATELY. pipet 50.0 ml of thereduced standard or sample into a clean,labeled. 100 + ml flask or beaker. (NOTE:Nitrite can oxidize back to nitrate).

13 Add 2.0 ml color reagent and 'Mix thor-oughly by swirling.

19 The mixture should stand at least 10minutes. and not more than two hoursbefore spectrophotometric measurements.This allows time to repeat steps 2 through13 for each standard and sample so allspectophotometric measurements can bedone at the same time. (More than onecolumn can be used by analysts experi-enced in performing the test).

15 Repeat steps 2 through 14 for each stand-ard and sample.

D Spectrophotometric Measurements

1 Absorbance measurements must be madewithin two. hours of the addition of thecolor reagent..

a The instrument must be warmed up.

b Use the 590 nm wavelength.

c Use the 0.00 mg /liter itrate-nitrogen standard (reagent blank)to calibrate the instrument.

2 Record the absorbances to Table 1(A.2. above) next to the correspondingconcentrations of the standards. A

25-8

space is also provided for recordingthe absorbance of the sample.

E Calibration Curve

1 Obtain a piece of graph paper andlabel the axes. The longer sideshould be labeled with the concentra-t.ons of the standards as given inTable 1. The shorter axis is labeled

axis.0.00to 1.00 as the absorbance

2 Use the abaorbances recorded Tor thestandards in Table 1 and4he correspond-ing concentration of the standards toplot a calibration curve.

3 Title the graph. "Total Nitrate PlusNitrite."

F Results

1 Use the absorbance value recorded inTable 1 for the sample to find the con-centration of total nitrate plus nitritenitrogen from the curve.

2 If a dilution was used, calculate thedilution factor and apply it to the con-centration you found for the sample byusing the curve.

a

b

Dilution Factor =

100 mlml sample used in dilution

Example: You diluted 25 mlsample to 100 ml. The con-centration found by using thecurve was 0.9 mg/liter. Them

Total NO3+ NO2-N mg/1 =

100 x 0.4 or 1.825

1

3 If more than one dilution was tested, use theresult that falls nearest the middle of the curve.

DETERMINATION OFNiTRATE/NITRITE NITROGEN (CADMIUM REDUCTION :METHOD)

VII Deterrhination of Nitrite

A Preparation of Nitrite CalibrationStandards

1 Mark six 100 ml volumetric flaskswith the concentrations listed inTable 2.

2 Using volumetric pipats, measurethe amounts of standard nitritesolution listed in Table 2 into thecorresponding 100 ml yolumetricflask.

TABLE 2

Use thesemls St'd NOTsou 100 ml

For thisconc., mg AbsorbanceNO2 -N./ 1.

0.0 ml0.5 ml1.0 ml2.0 ml5.0 ml10.0 mlSAMPLE

0.000.050.100.20r 40

' 1.00

3 Dilute each to ).e 100.0 ml mark,stopper and mix thoroughly.

4 Note: The fla.% containing 100 mldistilled water 3.00 mg NOR -N)-is the reagent blank.

5 Mark six 150 ml ,eakers with theconcentration:. in Table 2.

Tre.nefr en, calibration tandardto Utz beaks .

B pit ficl!ustment of Standards and Sample

1 You should pave. reserved 100-175ml of undiluted s'umple from VI)3(above).

a Nitrite concentratidns areusually well within the applica-bilityW this test so sampledilution is usually not required.

p

143

2 Usea meter to check the pH ofthe sample and of each nitritestandard solution. If necessary .

,adjust the pH to between 5 and 9with either conc. hydrochloricacid or conc. ammonium hydroxide.

,C Color Development

1 Label clean, 250 ml flasks withthe concentrations of the standardsor the sample code.

2 Pipet 25:0 mi of each standardand sample into the correspondingflask.

3 Add 75 ml dilute ammonium chloride -EDTA solution to each and mix wellby swirling.

4 Pipet 50.0 ml of each standard andsample mixture prepared in 2 and 3intcra clean, labeled 100+ ml flask.

5 Add 2.0 ml color reagent to eachand mix thoroughly by swirling,

6 Each mixture should Stand at least10 minutes (but not more than twohours) before spectrophotometricmeasurements.

D Spectr_,Ph ric Measurements

I The ins ment must be warmed up.

2 Use the 540 nM wavelength.

3 Use the 0.00 mg ter nitrite nitrogenstandard (reageny lank) to calibratethe Instrument.

4 Record the absortiances in Table 2(A2 . above) next to the carrespondleqrconcentrations of the standards. Aspace is also provided for recordingthe absorbance df the sample.

E Calibration Curve

1 Obtain a piece of graph paper andlabel the axes. The longer side'should be.labeled with the concentra-tions of the standards as given inTable 2- The shorter ails is labeledfrom 0.00 to 1.00 as the absorbance axis.

25-7

DETERMINATION OF NITRATE/NITRITE NITROGEN (CADMIUM REDUCTION 'METHOD)

2 Use the.absorbances recordedfor the standards in Table 2.and the corresponding concentra-tion of the standards to plot acalibration curve.

3 Title the "Nitrite"

F Results

I Use the absorbance valuerecorded in. Table 2 for,lhesample to find the concentra-tion of nitrite nitrogen fromthe curve.

2 A dilution was probably notnecessary. If it was required.calculate the dilution factorand apply it to the concentrationyou found for the sample }y using.the ,curve.

a Dilution Factor

final dilution volumeml sample used in dilution

VIII CHECKING COLUMN EFFICIENCY

A In order to validate results, check theefficiency of the reduction column bycomparing at least onexeduced nitratestandard to a nitrite standard of thesame concentration.

1 % efficiencyi

absorbance'of NO,St'd100absorbance of NO2St'd*

* Standards of equal concentration

2 The value ie acceptable if it isbetween 96 and 104%.

3 The best representation of columnefficiency ie the average of the %efficienclea, calculated by comparingevery,pair (5) of NO3 and NO2 standardsof equal concentration.

)3 If the column efficiency is acceptable.report the results as required. SeeSection IX.

C If the % efficiency of the reductioncolumn is not within the acceptablerange, you should remove the copperizedcadmium from the column, adcloothw gramsof cadmium (new or used) and repeat allof section IV, ''Preparation of ReductionColumn" (above).

IX REPORTING RESULTS

The results from this test can be used in avariety of ways to report nitrate-nitriteconcentrations.

A Total Nitrate plus Nitrite Nitrogen

/1 Report the results from section VI F

B Nitrite Nitrogen

1 Report the results from section Vil F

C Nitrate Nitrdgen

1 Subtract the result for nitrite nitrogen(VII F) from the result for total nitrateplus nitrite nitrogen (V1 F) for eachsample.

Nitrate

1 Calculate the concentration of nitratenitrogen in the sample as describedIn C. (above).

2 Multiply this concentration by .4.43

E Nitrite

1 Multiply the result for each samplefrom section VII F by 3.29

144


REFERENCE

1 Methods for Chemical Analysis of Waterand Wastes. 1974. U. S. EPA. MDQAR L.Cincinnati. Ohio 45268

This outline was prepared by Audrey D.Kroner, Chemist. National*Training andOperational Technology Center, USEPA.Cincinnati. Ohio 45268

Descriptors: Analytical Techniques.Chemical Analysis. Laboratory Tests.Nutrients. Nitrate. Nitrite, Nitrogen.Water Analysis

c.

1.45 25-9

r.

LABORATORY PROCEDURE FOR TOTAL SOLIDS

I INTRODUCTION

A This procedure was elcerpted from methodsfor Chemical Analysis of Water and Wastes,1974, Environmental Protection Agency,Office of Water Programs, Analytical QualityControl Laboratory.

B

C

D

E

1,1

A

B

C

DJE

F

G

ID

A

The procedure is applicable to surface andsaline waters, domestic and industrial wastes.

The practical range of the determination is10- 20,000 mg/ 1.

Nonhm-nogenous materials (large floatingparticles or submerged agglomerates) shouldbe excluded from the sample. Floating greaseand oil should be included in the sample anddispersed in a blender before measuring thealiquot.00"."`

Samples should be analyzed as soon aspossible.

EQUIPMENT

Porcelain, Vycor, or platinum evaporatingdishes, 100 ml capacity; smaller sizes maybe used as'required,

Muffle furnace. 5502 50°C

Drying oven, 103 - 105°C

Desiccator

Analytical balance

Steam bath or Oven at 98°C

Graduated cylinder, 100 ml

PROCEDURE

Heat the clean 4vaporating dish in a mufflefurnace at 550 50°C for 1 hour.

B Cool the dish in a desiccator:.

PC:isb.183. 11.7714 u"

C Store the dish in the desiccator and weighjust before use.

D Weigh tl'n dish on an analytical balance.

E Shake the sample container vigorously.

F Measure 100 ml of the well mixed samplein a graduated cylinder. (At least 25 mgof residue should be obtained; less volumeof sample may tie used if the sample appearsto be high in solids content. If it is low insolids content, more sample may be added'to the dish after drying).

G Rapidly, but without spilling, pour thesample into the evaporating dish.

H Dry the sample on a steam bath, or at 98°C(to prevent boiling and splattering) in theoven.

I Dry the egaporated sample in the oven at103 - 105 C.for at least one hour.

J Cool the dish in the desiccator and thenweigh it.

K Repeat .the heating at 103 - 105°C, coolingand weighing until the weight loose(' agreewithin 0.5 mg.

TV CALCULATIONS

mg total solids /1 (wt dish + residue). -(wt dish)*'x 1000 x 1000

ml of sample

* In grams

This outline was prepared by C. R. Feldmann,Chemist. National Training and OperationalTechnology Center. MOTD, OWPO. USEPA.Cincinnati, Ohio 45288.

Descriptors: Analytical Techniques." ChemicalAnalysis. Laboratory Tests. Solids. WaterAnalysis

28-1

LABORATORY PROCEDURE FOR NONFILTERABLE (SUSPENDED) SOLIDS

I INTRODUCTION

A This procedure was excerpted from Methodsfor Chemical Analysis. of Water and Wastes,1974, Environmental Protection Agency.Methods Development and QualityAssurance Laboratory.

The procedure is applicable to surface andsaline waters, domestic and industrial wastes.

C The practical range of the determination is10 - 20000 trig/l.

All nonhomogeneous particulates (such asleaves. sticks, fish and lumps of fecal matter)should be excluded from the sample.

Sample preservation is not practical; theanalysis should be done as soon as possible.

II EQUIPMENT

A Glass fiber filter discs. 4.7 cm or 2.2cm,without organic binder, Reeve Angel type98411. 934A, Gelman type A, or equivalent.

B Membrane filter funnel (to, use with the 4.7cm .11s, ), or 25 ml Gooci. crucible (for usewith the 2.2 cm disc, crucible adapter.

C Graduated cylinders, 2S ml and lOoml.

D 500 nl suction flask with hose and pinch clamp

E Drying oven. 103 - 105°C

F Desiccator

G Analytical balance, 200 g rapacity. capabilityo: weighing to 0.1 mg.

III PROCEDURE

B Apply suction to the flask and wash thedisc with three successive 20 ml portionsof distilled water.

C Continue the suction until all water haspassed through the disc.

D Remove the Gooch crucible plus 2.2 cm discand dry in the oven at 103 - 1.05°C for onehour. or,

E Remove the 4.7 cm disc from tile membranefilter funnel and dryin the oven at 103 - 105°Cfor one hour. In D or E. if the disc is notto be used immediately; store it in thedesiccator.

F Weigh the 4,7 cm disc or 2.2 cm disc plusGooch crucible just before use.

Assemble the filtering apparatus. 1

II Apply suction to the flask.I Wet the filter disc.J Shake the sample container vigorously.

K Measure 100 ml of the well Mixed sample. in a 100 ml graduated cylinder, (If the

sample appears to be low in solids, alarger volume maybe used).

L Rapidly, but without spilling, pour thesample into the funnel or crucible.

A Assemble the filtering apparatus and suctionflask (either the 2.2 cm disc. Gooch crucibleand adapter, or the 4.7 cm disc and membranefilter funnel).

PC. lab. 17a. B. 77

M Continue the suction until 311 of the water.has passed through the disc.

N Rinse the solids with distilled water.O Remove the 4.7 cm disc from tie funnel,

and dry in the oven at 103 - 105 C toconstant weight, or

P Remove the Gooch crucible plus 2.2 &mdisc and dry in the oven at 103 - 105 Cto constant weight.

Note:

I4;

Drying to constant weight refers to theprocess of:

1) drying the disc (br disc plus crucib Ile)at 103 - 105°C. 2) cooling in the slesitcator,3) weighing. 4) repeating steps IL 2). and3). If there is no difference in the two

27-1

Laboratory Procedure for Nonfilterable (Suspended) Solids

final weights, the disc (or disc pluscrucible) has bens dried to constantWeight. Weights that agree within0.5 mg are acceptable. In practicethe initial drying period is sometimes .extended to several hours to ensure completedrying.

IV CALCULATIONS

mg nonfilterable (suspended) solids/1

ivrt of 4.7 cm disc + residue)* - (vrt of 4.7 cm disc)* x 1000 x 1000I ml of sample filtered

or

'(wt of 2.2 cm disc + Gooch crucible + residue)* - (wt of 2.2 cm disc :r Gooch crucible)*x 1000 x 1000ml of sample filtered

1

*in grams

REFERENCE.

I. Methods for Chemical Analysisof Water and Wastes, 1974. U.S.EPA. MDC)ARL, Cincinnati, Ohlo45268.

This outline was prepa_red by g RFeldmann, Chemist, Naioal Trainingand Operational,Technology Center,MOTD, OWPO. DSEPA,Ngincinnati,Obio '45288

Drrriptors: Analytical Techniques,Chemical Analysis, Laboratory Tests,Solids, Water Anilysla

4^,

27-2

CALIBRATION AND USE OF A T.UF31131111ETER (NEPHELOMETER) ,

I REAGENTS(I)

A Turbidity - free water - Pasa distilledwater through a 0.45 um pore sizemembrane' filter if such filtered wafershows a lower turbidity than the originaldistilled water.

B Stock Tuibidity Suspension - 400 units

. Stability: Prepare a new standards,suspension each week. II%

E Secondary Standards

1 Directions are forpreparing 100.0 ml.Larger volumes may be required.

2 Solution, 1: Dissolve 1.00g hydrazine,sulfate. (NH2)2 H2SO4. in turbidity

free water and dilute to 100m1 in avolumetric flask.

3 Solution 2: Dissolve io.00ghexamethylenetetramine in turbidity-

. free water and dilute to 100m1 in avolumetric flask.

4 Suspension: Mix 5.0m1 Solution 1with 5.0m1 Solution 2 in a 100 mlvolumetric flask. Allow to stand for24 hours at 25 i VC. Dilute to themark and Inez.

5 Stability:. Prepare a new stocksuspension each month.

C Standard Turbidity Suspension - 40 units

1. Dilute 10.00m1 stock turbiditysuspension to looml witIrturbidity -free. water in a 100 ml volumetric flask..The turbidity is defined as 40 units.

2 Stability: Prepare a new standardsuspension each week.

D Dilute Standard Turbidity.Susir nsion --4 units

1 Dilute 0 ml stock turbiditysuspension to 190 ml with turbidity.-free water in a 100 Tel volumetricMask. The turbidity should be 4 units.

CH. TUBB. lab'.1.11.77

1 Solutions standardized with Formaican bepurchased from the manufacturerof the instrument.

2 Date such solutions. Store under theconditions specified. Discard andreplace when flocculation in'thesolution is observed or when it (sitea periodic dheck with a Formazin'Standard

(2)(3). II PREPARATIONS FOR MEASUREMENTS

A Suspensions

1 Check date of prepaiation and pre-pare fresh solutions if required.

B Sample C11

1 Cells should be cleaned immediatelyafter use as described in V. B. below.

1:19

2 Inspect cells for cleanliness. Ifnecessary. clean them using V. B.' below.

3 Check cells for'scratcbes aid etching..Discard those with imperfections.

Instrument

1 Scale - If a scale is inserted. checkthat it is in the correct position. Ifthe scale is blank, construct acalibration scale for each range on.the instrument. (See III B).

2 Zero,- Adjust meter needle to zeropgnt on /scale as, directed by roantifactuer.

3 Lela - Check for cleanness. if required.follow manufacturer's instructions forremoving and cleaning the lens.Accurate re-positioning of the lens iscritical for accurate measurements...,

ale.28-1

Calibration and Use of a Turbidimeter (Nephelometer).

4 Warm-Up Period - Followmanufacturer's instructions.Continuous running is often suggestedbecause of the photomultiplier tubes.

5 Focus. - Use template or methoddescribed by manufacturer to checkand6 if necessary, set the focus.

..

D Determine Range of Sample Turbidity\1

1 Use steps 5 through 16 in III'A belowEXCEPT Step 12 which should be:Obtain a turbidity reading from thescale. r"

2' Note which Range (instrument scale) .

best "brackets': the turbidity 4 eachsample.

3 If the turbidity of a sampliv exceeds40 units. use the higher leales pro-vided to determine the dilution requiredso the final reading will be below

.410 units. For final measurements, usethe Range (Scale) appropriate for thediluted sample.

Ill INSTRUMENT CAWBRATION AND

MEASUREMENTS(1)

A Pre-Calibrated Scale,

1 Each day, prepare at least onestandard for the required instrument 'range (s) (as determined in II. D., above)by orlutlng one'of the Formazinsuspensions described above in I, Reagents.The table beloW gives "EXAMPLEDILUTIONS".

2 Set the instrument RANGE knob atthe first range to be tested. (Theinstru0ent !should beiON. warmed up,zeroed. etc.. as in ll'C above).

Make any instrument adjustment specifiedby the manufacture' to use this RANGE.

4 Rinse the SAMPLE CELL 3 times withthe'appropriate suspension (or sample).

5 Shake the suspension to thoroughlydisperse the solids. (For secondary,standards. check the manufacturer's

a:

EXAMPLE DILUTIONS i.

NO.

.

EXAMPLE .INSTRUMENTRANGES VOLUME

TURBIDITYSTANDARD

FINALDILUTION

..

FINALTURBIDITY

1 0 - 0. 1 2.S ml 4 unit 100.0 ml2 0 - 0. 2 5.0 ml 4 unit 100.0 ml 0. 2

3 0 - 0. 3 7.5 ml 4 unit 100.0 ml 0.3.4 0 - 1 2.5 ml 40 unit In. 0 ml

5 o - 3 7.5 ml 40 unit 100.0 ml 3 .

6 0 - 10 25.0 ml 4Q unit 100.0 ml 10 .7 0 - 30 7.5 M1 400 unit 100.0 ml 30

6 0 - 100 2 5 ml 400 unit 100.0 ml : 1009 0 - 300 75 ml 400 unit' 100.0 ml 300

10 0 - 400 100 ml 400 unit 100.0 nil 400

408 ,11 0 - 1000. 100 ml . 4p0 unit 771)).0 ml ,

28-215

Calibration and Use of a Tubidimeter (Nephelometerl

6 Wait until air bubbles disappear inthe suspension.

7 pour the suspension into theSAMPLE CELL up to the levelspecified by the manufacturer.CAUTION: Always hold the cellabove the area from which lightscattering is measured.

8 If applicable. screw cap on

Wipe the outside of the celliiiith a. .

lint-free tissue.

10 Examine the suspension in the cellto check for 'air bubbles: If airbubbles, are present. eliminate

14. Remove the SAMPLE CELL.

IS Dir sard the standard suspension.

16 Rinse Si7iirl-E CELL 3 times Withturbidity free water.

ti

by inserting the cell in the sampleholder and waiting a few minutesso bubbles rise above photo-.multiplier tube. CAUTION: Morebubbles can form if a temperaturerise occurs.

b by holding the cell at the top and:

1 flicking side with your finger or

2 dipping the end of the cell into anultrasonic cleaning bath or-

3 centrifuging the filled cell incups with rubber cuShionsandsurrounded with water.

-4 NOTE: After any of theseremedies. again wipe theoutside of the cell. When air -bubbles are gone, insert thecell in the sample holder.

11 Place the LIGHT SHIELD according tothe manufacturer's instruction;

12 Use the STANDARDIZING control toobtain a meter reading correspondingto the turbidity of the standardsuspension.

13 Remove the LIGHT SHIELD.

1

7 Use Steps 4 through 11 for ca/ hsample for diluted sample) to betested in this range. For samples.step 12 should be Record theturbidity reading r the sample.Then do Steps 134uoough 16 asabove.

NOTE: The final reading' for samplesshouldmot exceed 40 Nil'. If thisreading is exceeded for a sample.dilute it and repeat the calibration/measurement proCedure above usingthe appropriate range and standard.(Selection of the range as describedin II. D. above should make thisunnecessar). at tnis stage of theprocedure).

B Non-Calibrated Scale

Piepae a series of standards andmnke a calib'ration scale for eachrange of the instrument.

a The instrument should be ON.warmed up, zeroed, etc., asin II C' above.

b Prepare enough standards togive several points on eachscale so estimated readings canht. reasonably accurate.

c Use the table of EXANIPLEDILUTIONS in III A above toprepare the highest standardfur each instrument range.The rest of each' calibratingseries can also be preparedby dilutions based on the in-formation in tne table.

2 Self-prepared sca,es should alsobe calibrated each day using theprucedu,e given in III A above forpre-calibrated scales.

28-3

Calibration and Use of a Turbidimeter (Nephelometer)

selfprepared scales are used forsamples the manner described inIll A abo-z for pre-calibrated scales:

IV CALCUL; ION/ RESULTS(

biluted Samples

Multiply final sample readings by theappropriate dilution factor,

It Reporting Results.

Report results as follos:s:.

3 Observe stability times noted foreach in I. above.

I3 Sample Cells

NV; Report to Nearesi:

0,0 - 1.0 0. 05

I - 10. 0. 1

10 - 40 1

40 - 100 5

C100 - 400 10

400 - 1000 50

> 1000 100

C Precision and Accuracy

1 In a singlq laboratory (MDQAR12),using surface water samples atlevels of 26. 41. 75 and 180 NTU,the standar, .viations were + 0.60.+ 0.94. 1.2 and + 4.7 units.respectively.

2 Accuracy data is not available at this

V STORAGE

A Standard Suspensions..

1 Store in glass containers atzoomtemperature.

2 Excess light or heat may affectstability,

28-4 s\

1 Discard cells with scratches or .

etching.

2 Clean cells immediately after ii.rtewith this order of treatments-

a detergent

b organ:, solvents, if required

deionized water

d alcohol or acetone rinses todry

e lint-free tissue. if required

3 Store in a manner to pr'111teat thecells (Porn scratches.

Instrument

1 A line operated instrument shouldi5e permaneatly located so movingit often is not necessary.

2 Turbidimeters should be protectedfrom dust, especially the lens system.

:3 Store any removablz parts asdirected by manufacturer.

4 Close any access doors.

S Because of the photomultiplier tubes.the manufacturer may suggest con-tinuous running of the instrument toinsure maximum accuracy for mea-

Frequency of use candeterminz the actual routine for warm-up

6 Follow any other storage directionsin the manufacturer's manual.

Calibration and Use of a Turbidimeter (Nephelometer)

IIEFE It ENC ES

I 5lethods for Chemical Analysis ofWater and Wastes. EPA-NIDQA111...Cincinnati. Ohio 45268. 1974.,

2 Laboratory Turbidimeter, 1Iodel 2100A;Lich Chemical Co.. Ames., Iowa,

1973.

Turbidimeters. Information CircularNo. 373A, Fisher ScientificCompany. Pittsburgh. PA

4 Analytical Quality Control. EPA-AQCI.. Cincinnati. Ohio 45268.1972

4

This outline was prepared by Audrey D.Kroner. Chemist, National Training and'Operational Technology Center. SIOTD,O0'PO. 1.:SEPA. Cincinnati. Ohio 45268.

Descriptors: Analytical Techniques,Laboratory Tests. Turbidity'

28-5

CALIBRATION AND USE OF A CONDUCTIVITY METER

I EQUIPMENT AND REAGENTS

A Equipment

1 Solu'Bridge conductivity meters

2 Probes

a Cell VSO2

b Cell VS2

c Cell VS20

,3 Thermometers

4 400 ml beakers

B Reagents

1 Standard KC1 solutions

Normality of Specific CondUctanceKC1 Solution rnicrornhos/cm.

0.00010.0010.010,1

2 Distilled water

14.9147.0

1413.012900.0

II CHECKING THE INSTRUMENT

A The measurement of specific conductivityas presented in sections II and III iswritten for one type of conductivity meterand probe.

turning the specific conductance switch.The specific conductance reading shouldbe approximately 200 -micromhos/cm.

.111 DETERMINATION OF THE CALIBRATIONCONSTANT

A Determine the temperature of thestandard KC1 solutions and move thetemperature knob to that value.

B Connect probe Cell VS02. to the con-ductivity meter. .

C Rinse the probe in the beaker ofdistilled ;eater, wipe the excess waterwith a kimwipeand place probe in thefirst beaker of KC1 solution (0.0001 N).

D Make certain the cell ie submerged toa point at least 1/2 inch above the airhole and that no entrapped air 'remains.

-The cell should also be at least 1/2inch from the inside walls of the flask.

E Press and hold down the ON-OFFbutton, simultaneously rotating the mainscale knob until the meter reads zero.Release the button. (If the meter needleremains off scale or cannot be nulled,discontinue testing in that solution.)

Record the scale reading in Table 1 andproceed to KC1 solutions 0.001N,0.01N, 0.1 N using Steps C. D and E.

Repeat steps C through F using the VS2,then the VS20 prole.

B A battery cneck is/ made by depressing Ilkthe Battery Check switch; and at thesame time pressing the on-off .button.The meter needle should defIrct to theright (positive) and come to rest in thegreen zone.

C Place a 10,090 ohm resistor in the holesof the electrical contacts on the meter.Turn the teroperature knob to read 25°C.Depress the on-off button and bring themeter needle to a reading of 0 by

H

15,1

Compute the cell calibration constant-afactor by which scale readings must bemultiplied to compute specific conductance:K = cMspwhere K = actual specific conductance,c = calibittion constantM..' meter reading

(continued next page)

CH. COND. lab. 3c. 11.77 29

Calibration and Use of a Conductivity Meter

TABLE I DATA FOR CALIBRATION CI'NSTANTS--,..----- ---y

Pru.e Cell VS02 Cell VS2 cell VS20

NCISelutann 0.00oIN 0.0015 0.015 0.IN 0.00015 0.0015 0.0I5 0.1N mewls 0.0015 0.015 0.15

-frst / .

Cell -

Constani

For each cell, calculate the cell constantby using the meter reading closes+ to the400 - 600 range. The known specificconductance for the corresponding KC1solution can be found in IB Reagents. Recordthe cell constants on Table L.

IV DETERMINATION OF Ksp FOR SAMPLES

Obtain rr ter readings, M, for samplesA, B an C using Section III C, D and E.Record M in Tattle 2. See Table I forthe appropriate cell constant, c, tocalculate K.p for each sample whereKsp = cM. Record results in Table 2.

V EPA METHODOLOGY

The current EPA Manual") /Teethesusing the procedures found in References2 and 3. These procedures have beenadapted for this laboratory session andall are approved in 40CFR136 for NPDESreport purzoses.

29-2

TABLE 2.

ACKNOWLEDGMENT .

This outline contains certain portions ofprevious outlines by Messrs. J. W. Mandia,and J. R. Tilstra.

REFERENCES

1 Methods for Chemical Analysis of .Water and Wastes, USEPA. AQCL,Cincinnati, OH 45268, 1974.

2 Standard Methods forlhejtaminationof Water and Wastewater, 4thEdition. 1976.

3 Book of ASTM Standards, Part 31. 1975.

This outline was prepared by C. R. Feldn'ann.Chemist, National Training and OperationalTechnology Center. and revised by Audrey D.Kroner. also with National Training andOperational Technology Center. MOTD, OWPO.USEPA. Cincinnati. Ohio 45268.

Descriptors: Analytical Techniques, Conductivity.Electrical Conductance, Specific Conductivity.Water Analysis.

SPECIFIC CONDUCTIVITY TESTS

Sampler A B c

Probe CallVS02

ca tVS2

colV520

c. iiVS02

CallVS2

CellVS20`

CellVS02

CellVS2

CellVS2O

1..

.

CellConstant

.

Sp. Cond.amhosietn

1 5

LABORATORY SAFETY PRACTICES

I INTRODUCTION

A Safe Use, Handling and Storage of Chemicals

I Chemicals in any form can be safelystored. handled, and used if theirhazardous' physical and chemical

'properties are fully understood and thenecessary precautions, including theuse of proper safeguards and personalprotective equipment are observed.

2 The management of every unit within amanufacturing establishment must givewholehearted support to a well integratedsafety policy.

B General Rules for Laboratory Safety

I Supervisory personnel should think"safety." Their attitude toward fireand safety standard practices is reflectedin the behavior of their entire staff.

2 A safety program is only as strong asthe worker's will to do the correctthings at the right time.

3 The fundamental weakness of mostsafety programs lies in too much lipservice.to safety rules and not enoughaction in putting them into practice.

4 Safety practices should be practical andenforceable.

5 Accident prevention is based on certaincommon standards of education,. trainingof personnel and provision of safeguardsagainst accidents.

II LABORATORY DESIGN AND EQUIPMENT

A Type olConstruCtion

I Fire-resistant or noncombustible

2 Multiple story buildings should haveadequate means of exit.

PC. SA. lab. 1. 11. 77

3 Stairways enclosed with brick orconcrete walls

4 Laboratories should have adequate exitdoors to permit quick, safe escape inan emergency and to protect the .occupants from fires or accidents inadjoining rooms. Each room should bechecked to make sure there is nochance of a person being trapped byfire, explosions, or release of dangerousgases.

5 Laboratory rooms in whichiost of thework is carried out with flammableliquids or gases should be providedwith explosion- venting'windows.

B Arrangement of Furniture and Equipment

I Furniture should be arranged formaximum utilization of available spaceand should provide working conditionsthat are efficient and safe.

2 Aisles between benches should be atleast 4 feet wide to provide adequateroc= tor passage of personnel andequipment.

3 Desks should be isolated from benchesor adequately protected.

4 Every laboratory should have an eye-wash station and a safety shower. '

C Hoods and Ventilation

I Adequate hood facilities should beinstalled where work with highly toxicor highly flammable materials are used.

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2 Hoods should be ventilated separatelyand the exhaust should be terminatedat a safe distance from the building.

3 Make-up air should be supplied torooms or to hoodsito replace thequantity of air exh usted through thehoods.

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Laboratory Safety Practice

(Hood ventilation systems are best`designed to have an air flow of nos,lessthan 60 linear feet per canine acres,the face of the hood, with all doors open

' and 150, if toxic rnaterials are involved.

5 Exhaust fans should be spark-proof 11exhausting flammable vapors andcorrosive resistant if handling corrosifumes.

6 Controls for all services should belocated at the from of the hood andshould be operable when the hood dooris closed.

7 All laboratory rooms should have theair changed continuously at a ratedepending on the materials beinghandled.

D Electrical Services

1 Electrical outlets should be placedoutside of hoods to afford easy accessand thus protect them from spills and,...orrosion by gases.

2 Noninferchangeable plugs should beprovided for multiple electrical services.

3 Adequate outlets should be provided and trshould be of the three-pole type toprovide for adequate grounding.

E Storage

1 Laboratories should provide foradecjuatestorage space for mechanical equipmentand glassware which will be usedregularly.

2 Flammable solvents should not be Movedin glass bottles over one liter in size.Large quantities should be stored inmetal safety cane. Quantities requiringcontainers larger than one gallon shouldhe stored outside the laboratory.

3 Explosion proof refrigerators should beused for the storage of highly volatileand flammable solvent's.

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4 Cylinders of compressed or liquifiedgases should not be stored in thelaboratory.

Housekeeping

1 Housekeeping playban important rolein reducing the frequency of laboratoryaccidents. Rooms should be kept in aneat orderly condition. Floors, shelves,and tables should be kept free fromdirt and from all apparatus and chemi-cals not in use.

2 A cluttered laboratory is a dangerousplace to work. Maintenance of a cleanand orderly work space is indicative ofinterest, personal pride, and safety-mindedness.

3 Passageways should be kept clear to allquilding exits and stairways.

Metal c,...tainers should be provided forthe dtspcsal of broken glassware andshoula be properly labeled.

5 - narate approved waste disposal cans,Jrld be provided for the disposal or

waste chemicals.

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6 Flammable liquids not miscible withwater and corrosive materials, orcompounds which are likely to give offtoxic vapors should never be poured

the sink.

G Fire Protection

1 Laboratory personnel sliouid beadequately trained regarding pertinentfire hazards associated with theirwork.

2 Personnel should kr:ow rules of fireprevention and methods of cornhatiigfires.

3 Fire extinguishers (CO2 type) shouldbe provided at convenient locations arilpersonnel should be Instructed In theiruse.

4 Automatic sprinkler systems areeffective for the control of fires Inchemical laboratories.

)

Laboratory sMetyyractices

H :Alarms

1 An approved fire alarm system shouldtie provided.

2 Wherever a hazard of accidental releaseof toxi: gases exists, a gas alarm*system to warn occupants to evacuatdthe building should be \provided.

3 Gas masks of oxygen or compressed airtype should be located near exits andselected personnL trained to use them.

III HANDLING GLASSWARE.

A Receiving, Inspection and Storage

1 Packages containing glassware shouldbe opened and inspected for cracked ornicked pieces, pieces with flaws thatmay become cracked in use, and badlyshaped pieces.

2 Glassware should be stored on well-lighted stockroom shelves designed andhaving a coping of sufficient heightaround the edges to prevent the piecesfrom falling off.

B Laboratory Practice

1 Select glassware that Is designed for thetype of work planned.

2 Tu cut glass tubing, or a c.,d,:rnake astraight clean cut with a cutter or fileat the point where the piece Is to be

. severed. Place a towel over the pieceto protect the hands and fingers, thenbreak away from the body.

3 Large slze'tubing Is cut by means of aheated nlchrome wire looped around thepiece at the paint of severance.

4 When It Is necessary to insert b pieceof g4.as tubing or a rod through aperforated rubber or cork stopper,selectthe correct bore so that theinsertion can be made without excessivestrain,

k

15,;

5 Use electric mantels for heatingdistillation apparatus. etc.

To remove glass splinters, use awhisk broom and a dustpan. Verysmall pieces can be picked up with alarge piece of wet cotton.

1V GASES AND FLAMMABLE SOLVENTS

A Gas Cylinders

I Large cylinders must be securelyfastened so that they cannot be dis-lodged or tipped in any direction -

2 ConnectiOns, gauges, regulators orfittings used with other cylinders mustnot be interchanged with oxygen

- cylinder fittings because of the possi-bility of fire or explosion from areaction between oxygen and residualoil in'the fitting.

3 Return empty cylinders promptly withprotedtive caps replaced.

B Flammable Solvents

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1 Store in designated areas well' ventilated.

2 Flash point of a liquid is tne temperatureat which it gives off vapor sufficient toform an ignitible mixture with the air 'near.the surface of the liquid or withinthe vessel used.

.3 Ignition temperature of a substance isthe minimum temperature required to/MUMe or cause self-sustained com-bbstion Independently of the Heating orheated element.

4 Explosive or flammable limits. Formost flammable liquids, uses andsolids there is a minimum concentrationof vapor in air or oxygen below which -

propagation of flame does not occur L.'contact with a source of ignition,There is also,a maximum proportion oft.vapor or gas in air above which

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-Laboratory Safety Practices

propagation of flame does not occur.These limit mixtures of vapor or gaswith air, which if ignited will justpropagate flame, are known as the"lower and higher explosive or flammablelimits."

5 Explosive Range. The differencebetween the lower and higher explosiveor flammable limits, expressed interms of percentage of vapor or gas inair by volume is known as :he "explosiverange."

6 Vaor Density is the relative densityof the vapor as compared with air.

7 Underwriter's Laboratories Classificationis a standard classification for gradingthe relative hazaro of the variousflammable liquids. This classificationis based on the following scale:

Ether Class 100

Gasoline Class 90 - 100

Alcohol (ethyl) Class 60 - 70

'Kerosene Class " 10 - 40

Paraffin Oil 10 - 20

8 Extinguishing agents

V CHEMICAL HAZARDS

A Acids and Alkalies

1 Some,of the most hazardous chemicalsare the "strong'. or "mineral" acidssuch as hydrochloric, hydrofluoric,sulfuric and nitric.

2 Organic acids are less hazardousbecause of their comparatively lowionization potentials. However, suchacids as phenol (carboliz acid),hydrocyanic and oxalic are extremelyhazardous because of their toxicproperties.

3 Classification of acids

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B Oxidizing Materials

1 Such oxidizing agents as chlorates,eeroxides, perchlorates and perchloricacid, in contact with organic mattercan cause explosions and fire.

They are exothermic and decomposerapidly, liberating oxygen which reactswith organic compounds.

3 Typical hazardous oxidizing agents are:

Chlorine DioxideSodium ChloratePotassium ChromateChromium TrioxidePerchloric Acid

C Explosive Power

1 Many chemicals are explosive or formcompoundsthat are explosive andshould be treated accordingly.

2 A few of the more common examplesof this class of hazardous materials are:.

A cetylldesSilver Fulminate

`PeroxidesPeracetic AcidNitroglycerinePicric AcidChlorine and EthyleneSodium MetalCalcium Carbide

D Toxicity.

1 Laboratory chemicals improperlystored or handled can cause injury topersonnel by virtue of their toxicity.

2 Types of exposure. There are fourtypes of exposure to chemicals:a Contact with the skin and eyesb Inhalationc Swallowingd Injection

15a

c

VI PRECAUTIONARY MEASURES

A Clothing and Personal PrOtective Equipment

1 Chemical laboratories should havespecial protective clothing and equipmentreadily available for emergency use andfor secondary protection of personnelworking with hazardous materials.

2 Equipment should be provided for adequate:

a 'Eye protectionb Body protectionc Respiratory protectiond Foot protectione Hand protection

B Bodily Injury

1 Burns, eye'injuries, and poisoning arethe injuries with which laboratorypeople must he most Concerned.

laboratory Safety Practices

2 First emphasis in the laboratoryshould be on preventing accidents.This means observing all recognizedsafe practices using necessary personalprotectiv.2 equipment and exercisingproper control over poisonous sub-stances at the source of exposure.

3 So that a physjeian can be summonedpr:omptly, every laboratory should hav,posted the names, telephon.yonumbers,and addresses of doctors to be calledin an emerg6ncy requiring medical care.

REFERENCES

Guide for Safety in the Chemical Laboratory.the General Safety. .Committee of theManufacturing Chemists Association, Inc..Van Nostrand, New York (1954).

This outline was prepared by Paul F. Halbach.Chemist. National Training and OperationalTechnology Center. MOTD. OWPO, USEPA,Cincinnati, Ohio 45268

Descriptors: Safety. Laboratory. PracticesSafety. Laboratory Design Chemical Storage.Gas Cylinders. Flammable Solvents

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