basic analytical techniques in analytical chemistry laboratory abdul rohman laboratory of analytical...
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Basic Analytical Techniques in Analytical Chemistry Laboratory
Abdul RohmanLaboratory of Analytical Chemistry, Department of Pharmaceutical Chemistry, Gadjah Mada University, Indonesia
Contents
Weighing Procedures
Preparation of standard solution
Basic techniques in spectroscopic and Chromatographic
Method Validation
Weighing Procedure
The accurate results of our research are dependent to how appropriate we use an analytical balance to weigh the standards
There are two weighing techniques:
Weighing by difference
Weighing by addition
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TEKNIK MENIMBANGTEKNIK MENIMBANGWeighing by difference:
Wadah + zat = A gWadah + sisa = B gBerat zat = A - B g
Weighing by addition:Wadah ditimbang = C gWadah + zat = D gBerat zat = D - C g
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YOG-08. Gra
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N E R A C A
Jenis neraca Sensitivitas (mg)
Makro/analitik 0,1
Semimikro 0,01
Mikro 0,001
Sometimes, we find this term in paper
Weigh accurately of approximately 1.0 g samples equivalent to……
What is the meaning of the word accurately and approximately in the above sentence
Sensitivity of Analytical balance
0.1 mg
The balance sensitivity must be taken into account before performing a weighing
How much samples which are allowed to be weighed with a analytical balance having a sensitivity of 0.1 mg?????
In the procedure: approximately of 100 mg of samples is accurately weighed
Which balance (in term of sensitivity) must be used for weighing??????
Preparation of standard solutions
Molarity (M)= moles/liter or mmoles/mLNormality(N) = equivalence/liter or meq/mLFormality(F)= is identical to molarityMolality(m) = moles/1000g solvent
Expression of Analytical ResultsExpression of Analytical ResultsSo Many WaysSo Many Ways
%(wt/wt) = (wt analyte/wt sample)%(v/wt) = (volume analyte/wt sample)% (v/v) = (volume/volume)
Sometimes we must prepare standard solutions in molarity, normality or percentages
How to prepare one litre of sulfuric acid 0.1 N from sulfuric acid 96 %
How to prepare sulfuric acid 1 % (b/v) from sulfuric acid 98 %
Density CalculationsDensity CalculationsHow do we convert to MolarityHow do we convert to Molarity
Density = mass solute /unit volumeSpecific Gravity = Dsolute/DH20
DH2O = 1.00000 g/mL @ 4oCDH2O = 0.99821 g/mL @ 20oCDHCl = 1.19 g/mLDH2SO4 = 1.84 g/mL
The units ppm or ppb are used to express trace concentrations.
These are weigh or volume based, rather than mole based.
The units ppm or ppb are used to express trace concentrations.
These are weigh or volume based, rather than mole based.
. Volumetric flask.
Volumetric flasks are calibrated to contain an accurate volume. See the inside back cover of the text for tolerances of Class A volumetric glassware
Volumetric flasks are calibrated to contain an accurate volume. See the inside back cover of the text for tolerances of Class A volumetric glassware
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)
Transfer or volumetric pipets.
Volumetric pipets accurately deliver a fixed volume.
A small volume remains in the tip.
Volumetric pipets accurately deliver a fixed volume.
A small volume remains in the tip.
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)
Fig. 2.10. Measuring pipets.
Measuring pipets are straight-bore pipets marked at different volumes.
They are less accurate than volumetric pipets.
Measuring pipets are straight-bore pipets marked at different volumes.
They are less accurate than volumetric pipets.
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)
These syringe pipets can reproducibly deliver a selected volume.
They come in fixed and variable volumes. The plastic tips are disposable
These syringe pipets can reproducibly deliver a selected volume.
They come in fixed and variable volumes. The plastic tips are disposable
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)
Volumetric Analysis - Principles Standard Volumetric Analysis - Principles Standard Solutions Solutions
“Primary Standard “ – ◦highly purified compound used as a reference
material in titrimetryProperties:High purity Stable in airIndependent of relative humidityReadily availableReasonable solubilityLarge formula weight
Volumetric Analysis - Volumetric Analysis - PrinciplesPrinciplesExamples of Standard MaterialsExamples of Standard Materials
Primary Potassium Acid Phthalate KHC8H4O4 (FW 204.23) Benzoic Acid C6H5COOH (FW 122.12) Na2CO3 , KH(IO3)2
Arsenious Oxide (As2O3) Sodium Oxalate (Na2C2O4) KI , K2Cr2O7 , Fe(pure)
Secondary NaOH , KOH , Ba(OH)2
HCl , HNO3 , HClO4
Sulfamic Acid (HSO3NH2) KMnO4 , Na2S2O3
Ce(HSO4)4 (FW 632.6)
Volumetric Analysis-PrinciplesVolumetric Analysis-PrinciplesStandardization – involves establishing the
concentration of a “standard solution”Direct method: dissolve caarefully weighed quantity of primary
standard; dilute to known volumeIndirect methods:Titrate weighed quantity of primary standardTitrate weighed quantity of secondary standardTitrate measured volume of other standard
solution
Typical buret.
A 50-mL buret is marked in 0.1 mL increments.
You interpolate to 0.01 mL, good to about ±0.02 mL.
Two readings are taken for every volume measurement.
A 50-mL buret is marked in 0.1 mL increments.
You interpolate to 0.01 mL, good to about ±0.02 mL.
Two readings are taken for every volume measurement.
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)
Meniscus illuminator.
Position the black field just below the meniscus.
Avoid parallax error by reading at eye level
Position the black field just below the meniscus.
Avoid parallax error by reading at eye level
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)
Proper technique for titration.
Place the flask on a white background.
Place the buret tip in the neck of the flask while your swirl
Place the flask on a white background.
Place the buret tip in the neck of the flask while your swirl
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)
Preparation of standard solution
Making a calibration curves
Measurement of analyte of interest
Quantification of analytes using selected quantification techniques
Spectroscopic Technique
The commonly spectroscopic techniques used in Food analysis are:
Spectroscopy UV for transparent solution. For example analysis of DNA at 260 and 280 nm
Spectroscopy visible for measurement of colouric solution. For example determination of amino acid using Lowry method.
The commonly spectroscopic techniques used in Food analysis are:
Spectroscopy UV for transparent solution. For example analysis of DNA at 260 and 280 nm
Spectroscopy visible for measurement of colouric solution. For example determination of amino acid using Lowry method.
The technique for both spectroscopic is different
Absorbansi
waktu pengukuran
waktu operasional
Operational time in Visible spectroscopy
Quantification Techniques
External Standard
Internal standard
Internal Normalization
Standard Addition
Standar Eksternal
x
x
x
x
x
Konsentrasi baku
5
10
15
20
25
1,0 2,0 3,0 4,0 5,0
respon sampel
konsentrasi sampel hasil interpolasi
respon detektor
0,0
Konsentrasi baku etanol (ppm) Luas puncak (y)
0,50441,0091,5132,0182,522
1799436109541217198889984
y = bx + a y = respon detektorx = konsentrasi
Kita bisa menghitung konsentrasi sampel dengan memasukkan luas puncak (y) sampel lalu memasukkannya ke persamaan regresi linier
Standar internal
Kadar diazinon
(ppm) (x)
Luas puncak diazinon
Luas puncak paration
Luas puncak diazinon/ Luas puncak paration (y)
6,534 11672 8901 1,31129730
9,801 16868 9213 1,83093824
13,068 25930 9418 2,753275216
19,068 36877 8714 4,231929888
26,136 54384 9019 6,029886393
Normalisasi Internal
Normalisasi Internal Ada dua hal yang harus diperhatikan :
(i) kita harus yakin bahwa kita telah menghitung semua komponen
(ii) kita harus mengasumsikan bahwa kita memperoleh respons detektor yang sama untuk setiap komponen. Untuk mengatasi kesulitan ini, maka diperlukan kalibrasi detektor.
Standard Addition
Method Validation
Precision
Accuracy
Limit of detection
Limit of quantification
Spesificity
System suitability
Linearity
Kisaran (range)
Robutness
METHOD VALIDATION
How to determine limit of detection (LOD) and limit of quantification (LOQ) for sensitivity????
YOG-08. HPLC 37
YOG-08. HPLC 38