l e c t u r e 1l e c t u r e 1l e c t u r e 1l e c t u r e 1 analytical chemistry. chemical...

LL ee cc tt uu rr ee 11

Analytical chemistry. Analytical chemistry.

Chemical analysisChemical analysis..

Associate profAssociate prof . L.V. Vronska. L.V. VronskaAssociate profAssociate prof . M.M. Mykhalkiv

OutlineOutline1. Object and task of analytical chemistry. Chemical 1. Object and task of analytical chemistry. Chemical

analysis and its varieties. The importance of analysis and its varieties. The importance of

analytical chemistry in analytical chemistry in Pharmacy. Methods of . Methods of

analysis, their classification.analysis, their classification.

2. Main principles in the theory of strong electrolytes.2. Main principles in the theory of strong electrolytes.

3. The Law of Mass Action3. The Law of Mass Action in analytical chemistry. in analytical chemistry.

Main types of chemical equilibrium, which are Main types of chemical equilibrium, which are

utilized in analytical chemistry.utilized in analytical chemistry.

4. Bronsted-Lowry theory of acids and bases.4. Bronsted-Lowry theory of acids and bases.

1. Object and task of analytical 1. Object and task of analytical chemistry. Chemical analysis and its chemistry. Chemical analysis and its

varieties. The importance of varieties. The importance of analytical chemistry in analytical chemistry in PharmacyPharmacy. .

Methods of analysis, their Methods of analysis, their classification.classification.

Analytical chemistryAnalytical chemistry – a sub-discipline of – a sub-discipline of

Chemistry about methods of the analysis or Chemistry about methods of the analysis or

methods of reception of the information about methods of reception of the information about

elementary objects.elementary objects.

Analytical chemistryAnalytical chemistry a sub-discipline of a sub-discipline of

Chemistry which develops theoretical basis and Chemistry which develops theoretical basis and

methods of the chemical analysis.methods of the chemical analysis.

ObjectObject of analytical chemistry is to define of analytical chemistry is to define

chemical compounds in substances.chemical compounds in substances.

Main divisions of Analytical Main divisions of Analytical Chemistry:Chemistry:

The qualitative analysis: fractional and The qualitative analysis: fractional and systematic methodssystematic methods

The quantitative analysis:The quantitative analysis:

1. chemical methods1. chemical methods

2. instrumental methods:2. instrumental methods:

- physical methods of analysisphysical methods of analysis

- physical-chemical methods of analysisphysical-chemical methods of analysis

Aliquots identical mixtures

Reagent F

Reagent W Reagent Q

Scheme of Fractional Analysis of Complex Mixtures

Component I Components J M

Mixture of components I, J, K, L, M groups

ComponentsI M

ComponentsI M

ComponentsI M

ComponentsI M

ComponentsI M

Component J Components I, K, L, M

Component L

Components I, J, K, M

Scheme of Systematic Path of Complex Scheme of Systematic Path of Complex Mixture AnalysisMixture Analysis

Mixture of substances of I, J, K, M group

Group IComponents I1, I2, I3 …

Mixture of substancesof groups J … M

Group JComponents J1, J2, J3

…

Mixture of substancesof groups K, M

Reagent A

Reagent B

Scheme of Analysis of Group Scheme of Analysis of Group JJComponents J1, J2, J3, J4, J5

Components J1, J2 Components J3, J4, J5

Component J3

Components J4, J5

Component J4 Component J5

Component J1 Component J2

Reagent Y

Reagent N

Reagent Z

Reagent T

The main goal of the qualitative analysis is The main goal of the qualitative analysis is

searching of elements, ions or chemical searching of elements, ions or chemical

compounds that are contained in the investigated compounds that are contained in the investigated

substance.substance.

The main goal of the quantitative analysis is to The main goal of the quantitative analysis is to

define the quantity of the mixture ratio or define the quantity of the mixture ratio or

percentage of elements (ions) in substance. percentage of elements (ions) in substance.

Reactions in analytical chemistryReactions in analytical chemistry

Specific Specific SelectiveSelective

Specific reactions give an analytical effect only with one individual substance.

NH4+ + OH - = NH3 + H2O.

Selective reactions give identical or similar analytical effects with small number of ions (2-5). HCl: Pb2+ + 2Cl- =PbCl2↓

Ag+ + Cl- =AgCl ↓Hg2

2+ + 2Cl- =Hg2Cl2 ↓

•The The group reagentgroup reagent is the reagent which will is the reagent which will meet the following requirements:meet the following requirements:

•It should It should precipitate cationsprecipitate cations virtually, virtually, quantitatively (concentration of cations in a quantitatively (concentration of cations in a solution should be less than 10solution should be less than 10-6-6 M); M);

•The precipitate should be easily dissolved in The precipitate should be easily dissolved in certain reagents;certain reagents;

•Excess reagent should not alter determination Excess reagent should not alter determination of those ions which remain in solution.of those ions which remain in solution.

Tasks of analytical chemistry:Tasks of analytical chemistry: Research methods of qualitative and quantitative Research methods of qualitative and quantitative

analysis of analysis of Nb, Ta, Zr, Ti, Hf, Mo, WNb, Ta, Zr, Ti, Hf, Mo, W, , rare-earth rare-earth andand other other elementelements in mixture, because s in mixture, because they are they are used in the modern techniquesused in the modern techniques..

Research methods Research methods for detection and definition of for detection and definition of

microquantities of elementsmicroquantities of elements, because often , because often physical and chemical properties of materials are physical and chemical properties of materials are predetermined by their presence.predetermined by their presence.

Detect and Define chemical elements and Detect and Define chemical elements and substances in the environment: soil, air, water, substances in the environment: soil, air, water, plantsplants

Investigate the complex influence of related Investigate the complex influence of related substances on a life of plants, animals and people.substances on a life of plants, animals and people.

The Importance of analytical chemistry in The Importance of analytical chemistry in PharmacyPharmacy..

Synthesis of drugs (synthetic or natural) is Synthesis of drugs (synthetic or natural) is necessarily supervised by methods of analytical necessarily supervised by methods of analytical chemistry. chemistry.

Definition of period of drugs validity is based on Definition of period of drugs validity is based on methods of analytical chemistry. methods of analytical chemistry.

Chemical analysis and its Chemical analysis and its varieties:varieties:

Elemental analysisElemental analysis Function analysisFunction analysis Molecular analysisMolecular analysis Phase analysisPhase analysis Diffraction analysisDiffraction analysis

Elemental analysisElemental analysis is qualitative and quantitative is qualitative and quantitative analysis of elements in compound clear substanceanalysis of elements in compound clear substance

Function analysisFunction analysis is the analysis which answer is the analysis which answer what functional groups are contained in what functional groups are contained in investigated substanceinvestigated substance

Methods of the Methods of the molecular analysismolecular analysis receive the receive the information about substances which consist information about substances which consist of molecules or formular parts.of molecules or formular parts.

Phase analysisPhase analysis – detection and definition of – detection and definition of different phases (solid, liquid, gas), which are different phases (solid, liquid, gas), which are contained in the investigated system.contained in the investigated system.

Diffraction analysisDiffraction analysis determines the crystal lattice determines the crystal lattice structure containing atoms, molecules and structure containing atoms, molecules and ions.ions.

Pharmaceutical analysis is determination of Pharmaceutical analysis is determination of drug quality (manufactured or pharmacy drug quality (manufactured or pharmacy

compounded)compounded)

Pharmaceutical analysis includes:Pharmaceutical analysis includes: analysis of drugsanalysis of drugs analysis of medicinal herbsanalysis of medicinal herbs process monitoring of drugsprocess monitoring of drugs toxicological analysistoxicological analysis judicial-chemical analysisjudicial-chemical analysis

IUPAC Classification of analytical methods in IUPAC Classification of analytical methods in accordance with mass and volume of analytic accordance with mass and volume of analytic

samplesampleMethod nameMethod name Mass of sample, gMass of sample, g Volume of sample, Volume of sample,

mlml

Gramm-methodGramm-method 1–101–10 10–10010–100

Cantigramm-methodCantigramm-method 0,05–0,50,05–0,5 1–101–10

Milligramm-methodMilligramm-method 1010-6-6–0,001–0,001 1010-4-4–0,1–0,1

Microgramm-methodMicrogramm-method 1010-9-9–10–10-6-6 1010-6-6–10–10-4-4

Nanogramm-methodNanogramm-method 1010-12-12–10–10-9-9 1010-10-10–10–10-7-7

Picogramm-methodPicogramm-method 1010-12-12 1010-10-10

The signal which bears the information on The signal which bears the information on elementary objects, is called as an elementary objects, is called as an analytical analytical signalsignal..

The analytical signal can be the carrier for both The analytical signal can be the carrier for both qualitative and quantitative information.qualitative and quantitative information.

Sensitivity of analytical reactionSensitivity of analytical reaction is the least is the least amount of substance, which can be detected with amount of substance, which can be detected with the reagent in one drop of solution.the reagent in one drop of solution.

The sensitivity express to next correlated values:The sensitivity express to next correlated values:

Limit of detection = Determined minimumLimit of detection = Determined minimum (m) (m) – the least amount of substance, which present in – the least amount of substance, which present in analysed solution and can be detected with the analysed solution and can be detected with the reagent. Calculatereagent. Calculatedd in in g. 1 g. 1 g = 0,000001 g.g = 0,000001 g.

Limit of concentration = Minimal concentrationLimit of concentration = Minimal concentration (C(Cminmin) – the least concentration of substance in the ) – the least concentration of substance in the

solution which still can be detected in small solution which still can be detected in small portion or volume of analysed solution.portion or volume of analysed solution.

Maximum of dilutionMaximum of dilution (W = 1/Cmin) – (W = 1/Cmin) – quantity (ml) of solution, containing 1 g of quantity (ml) of solution, containing 1 g of the analysed substance, which can be the analysed substance, which can be detected with a definite reaction (reagent).detected with a definite reaction (reagent).

Analytical reaction is considered more Analytical reaction is considered more sensitive under conditions when sensitive under conditions when determined minimumdetermined minimum and and minimal minimal concentrationconcentration of analyzed solution are low of analyzed solution are low and and maximum of dilutionmaximum of dilution is high. is high.

2. Main principles of theory of 2. Main principles of theory of strong electrolytes.strong electrolytes.

activityactivity (а)(а) – – effective concentrationeffective concentration of ions in of ions in solutionsolution, , when it reactswhen it reacts

.1lim0

C

a

C

To calculate activity coefficients use the following::

1. Ionic strength of solution

where ci and zi are the concentration and charge of the ith ion.

2. Activity coefficients for ionic solutes, depend on the ionic strength of solution by using the extended Debye–Hückel theory

22

1ii ZC

To calculate activity coefficients use the Debye–Hückel equation

ifif 0,01 0,01

ifif 0,1 0,1

ifif 1,0 1,0

,512,0lg 2 ii Zf

,1

512,0lg

2

i

iZ

f

,1,01

512,0lg 2

2

ii

i ZZ

f

Experimentally is possible to find Experimentally is possible to find only the Mean activity coefficient: only the Mean activity coefficient:

for binary electrolyte AB for binary electrolyte AB

for electrolyte structure for electrolyte structure AAmmBBnn

,BA fff

,nB

mA

nmfff

Mean activity coefficient may be Mean activity coefficient may be calculated theoretically by using calculated theoretically by using

Debye–Hückel equationDebye–Hückel equation:: ifif 0,01 0,01

ifif 0,1 0,1

ifif 1,0.1,0.

,512,0lg BAZZf

,1

512,0lg

BAZZ

f

.1,01

512,0lg

BABA ZZ

ZZf

For simplification of calculations of For simplification of calculations of activity coefficients use these activity coefficients use these

assumptions:assumptions:

1. Activity coefficients of ions with identical 1. Activity coefficients of ions with identical charge irrespective of ion’s radius are charge irrespective of ion’s radius are approximately equal. approximately equal.

2. Activity coefficients of neutral parts in dilute 2. Activity coefficients of neutral parts in dilute solutions of electrolytes equals 1.solutions of electrolytes equals 1.

3. Very dilute solutions of electrolytes are possible 3. Very dilute solutions of electrolytes are possible to consider ideal. to consider ideal.

3. The Law of Mass Action in 3. The Law of Mass Action in Analytical Chemistry.Analytical Chemistry.

ConcentrationalConcentrational ( (realreal) ) constantconstant of chemicalof chemical equilibriumequilibrium

nA + mB nA + mB lC +pD lC +pD

p-functionfunction of constantof constant equilibriumequilibrium

pK = –lgK.pK = –lgK.

.][][

][][mn

plR

BA

DCK

КТ – thermodynamic equilibrium constant (it depends on temperature and pressuretemperature and pressure)

where f – activity coefficientwhere f – activity coefficient

We use KWe use KRR, when we have real conditions , when we have real conditions (influence of ionic strength, temperature and (influence of ionic strength, temperature and pressure)pressure)

;m

Bn

A

pD

lCR

mB

nA

pD

lCT

ff

ffK

aa

aaK

ККC C – – conditionalconditional equilibrium constantequilibrium constant

where C – where C – formality, is a substance’s total concentration in solution regardless of its specific chemical form.

where where - - parts per mol

,mB

nA

pB

lCC

CC

CCK

.b

Ba

A

dD

cC

bB

aA

dD

cCTC

ff

ffKK

ionion C

ion][

We use KWe use KCC, when we have the following , when we have the following real conditions (influence of ionic real conditions (influence of ionic strength, temperature and pressure, strength, temperature and pressure, competitive reactions)competitive reactions)

Mass balance equation, which is simply a statement of the conservation of matter. In a solution of a monoprotic weak acid (base), for example, the combined concentrations of the conjugate weak acid (base), HA, and the conjugate weak base (acid), A–, must equal the weak acid’s (base’s) initial concentration, CHA.

H2S H+ + HS-

HS- H+ + S2-

CCSS = [S = [S2–2–] + [HS] + [HS––] + [H] + [H22S].S].

A charge balance equation is a statement of solution electroneutrality.

Total positive charge from cations = total negative charge from anions

Mathematically, the charge balance expression is expressed as

where [Mz+]i and [Az–]j are, respectively, the concentrations of the ith cation and the jth anion, and (z+)i and (z–)j are the charges of the ith cation and the jth anion.

The charge balance equation for an aqueous solution of Ca(NO3)2 is

2 [Ca2+] + [H3O+] = [OH–] + [NO3–]

Main types of chemical reactions which are Main types of chemical reactions which are used in analytical chemistryused in analytical chemistry::

Acid-base reactionAcid-base reaction ((the reaction of an acid with a

base))

CH3COOH(aq) + NH3(aq) CH3COO–(aq) + NH4

+(aq)

A precipitation reactionA precipitation reaction occurs when two or more

soluble species combine to form an insoluble product.

Pb2+(aq) + 2Cl–

(aq) PbCl2(s)

reaction between the metal ion and the ligand is

typical of a complexation reactioncomplexation reaction.

Cd2+(aq) + 4(:NH3)(aq) Cd(:NH3)4

2+(aq)

redox reactionredox reaction - an electron-transfer reaction.

2Fe3+(aq) + H2C2O4(aq) + 2H2O(l) 2Fe2+

(aq) + 2CO2(g)

+ 2H3O+(aq)

4. Bronsted-Lowry theory of acids 4. Bronsted-Lowry theory of acids and bases.and bases.

A substance, that dissolves in water to give an A substance, that dissolves in water to give an

electrically conducting solution is called an electrically conducting solution is called an

electrolyteelectrolyte. .

A substance, that dissolves in water to give A substance, that dissolves in water to give

nonconducting or very poorly conducting nonconducting or very poorly conducting

solution is called a solution is called a nonelectrolytenonelectrolyte..

According to According to Svante ArrheniusSvante Arrhenius concept: concept:

AcidAcid is any substance that, when dissolved in water, is any substance that, when dissolved in water, increase the concentration of hydrogen ion Hincrease the concentration of hydrogen ion H++..

BaseBase is any substance that, when dissolved in water, is any substance that, when dissolved in water, increase the concentration of hydroxide ion OHincrease the concentration of hydroxide ion OH––..

NaOH NaOH Na Na++ + OH + OH––

HCl HCl H H++ + Cl + Cl––

A useful definition of acids and bases was indepen-dently introduced by Johannes Brønsted (1879–1947)

and Thomas Lowry (1874–1936) in 1923.

acids are proton donors

bases are proton acceptors

Acid Acid Base + Н Base + Н++

Constant reaction of a dissociationConstant reaction of a dissociation solventsolvent hashas equationequation

AutoprotolysisAutoprotolysis constantconstant of solvent is product of solvent is product of activity lyonium and lyateof activity lyonium and lyate

.2

2

HSolv

SolvSolvHHSolv

T

a

aaK

,2

SolvSolvHTHSolv aaK

Neutrality of solution determines activity of Neutrality of solution determines activity of lyonium and lyate іons:lyonium and lyate іons:

Condition of neutralityCondition of neutrality

pSolvpHaaSolvSolvH

,2

THSolvpKpH 2/1

рН рН of some solventsof some solvents

SolventSolvent Limits Limits рНрН

HH22SOSO44 0 – 3,60 – 3,6

HCOOHHCOOH 0 – 6,700 – 6,70

HH22OO 0-140-14

CHCH33COOHCOOH 0 – 14,40 – 14,4

CHCH33OHOH 0 – 17,30 – 17,3

acetoneacetone 0 – 21,10 – 21,1

SolventSolvent Limits Limits рНрН

CC22HH55OHOH 0 – 19,000 – 19,00

CHCH33– C – C N N 0 – 19,000 – 19,00

lliiquid quid ammoniaammonia

0 – 22,00 – 22,0

FMAFMA 0 – 17,00 – 17,0

DMFADMFA 0 – 18,00 – 18,0

TheThe Brønsted-Lowry concept of acids and bases Brønsted-Lowry concept of acids and bases has greater scope than the Arrhenius concept:has greater scope than the Arrhenius concept: the general description of acid-base reactionthe general description of acid-base reaction possibility a quantitative estimation strength of possibility a quantitative estimation strength of

acid and baseacid and base

НА + ННА + Н22О О Н Н33ОО++ + А + А––

B + HB + H22O O BH BH++ + OH + OH––

HA

AOHTa a

aaK

3

B

OHBHTb a

aaK

SolventsSolvents::

progenic progenic (A species that can serve as a proton (A species that can serve as a proton donor)donor)

protophilic protophilic (A species that can serve as a (A species that can serve as a proton acceptor)proton acceptor)

amphiprotic amphiprotic (A species that can serve as both a (A species that can serve as both a proton donor and a proton acceptor)proton donor and a proton acceptor)

aproticaprotic (A species that can’t serve a proton)(A species that can’t serve a proton)

proton acceptor’s properties increase proton acceptor’s properties increase HH22SOSO44; CCl; CCl33COOH; CHCOOH; CH33COOH; HCOOH; H22O; CO; C22HH55OH; NHOH; NH33; C; C55HH55NN

proton donor’s properties increase proton donor’s properties increase

Thanks for your attention!