L e c t u r e 1

1
L e c t u r e 1
Analytical chemistry. Chemical analysis.
Associate prof . L.V. Vronska Associate prof .
M.M. Mykhalkiv
2
Outline

• 1. Object and task of analytical chemistry.
  Chemical analysis and its varieties. The
  importance of analytical chemistry in Pharmacy.
  Methods of analysis, their classification.
• 2. Main principles in the theory of strong
  electrolytes.
• 3. The Law of Mass Action in analytical
  chemistry. Main types of chemical equilibrium,
  which are utilized in analytical chemistry.
• 4. Bronsted-Lowry theory of acids and bases.

3

• 1. Object and task of analytical chemistry.
  Chemical analysis and its varieties. The
  importance of analytical chemistry in Pharmacy.
  Methods of analysis, their classification.
• Analytical chemistry a sub-discipline of
  Chemistry about methods of the analysis or
  methods of reception of the information about
  elementary objects.

4

• Analytical chemistry a sub-discipline of
  Chemistry which develops theoretical basis and
  methods of the chemical analysis.
• Object of analytical chemistry is to define
  chemical compounds in substances.

5
Main divisions of Analytical Chemistry

• The qualitative analysis fractional and
  systematic methods
• The quantitative analysis
• 1. chemical methods
• 2. instrumental methods
• physical methods of analysis
• physical-chemical methods of analysis

6
Scheme of Fractional Analysis of Complex
Mixtures
Aliquots identical mixtures Reagent
F Reagent W Reagent
Q
7
Scheme of Systematic Path of Complex Mixture
Analysis
Reagent A Reagent B
8
Scheme of Analysis of Group J
Reagent N
Reagent Y
Reagent Z
Reagent T
9
(No Transcript)
10

• The main goal of the qualitative analysis is
  searching of elements, ions or chemical compounds
  that are contained in the investigated substance.
  
• The main goal of the quantitative analysis is to
  define the quantity of the mixture ratio or
  percentage of elements (ions) in substance.

11

• Reactions in analytical chemistry
• Specific Selective

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
? Hg22 2Cl- Hg2Cl2 ?
12

• The group reagent is the reagent which will meet
  the following requirements
• It should precipitate cations virtually,
  quantitatively (concentration of cations in a
  solution should be less than 10-6 M)
• The precipitate should be easily dissolved in
  certain reagents
• Excess reagent should not alter determination of
  those ions which remain in solution.

13
Tasks of analytical chemistry

• Research methods of qualitative and quantitative
  analysis of Nb, Ta, Zr, Ti, Hf, Mo, W, rare-earth
  and other elements in mixture, because they are
  used in the modern techniques.
• Research methods for detection and definition of
  microquantities of elements, because often
  physical and chemical properties of materials are
  predetermined by their presence.

14

• Detect and Define chemical elements and
  substances in the environment soil, air, water,
  plants
• Investigate the complex influence of related
  substances on a life of plants, animals and
  people.

15
The Importance of analytical chemistry in
Pharmacy.

• Synthesis of drugs (synthetic or natural) is
  necessarily supervised by methods of analytical
  chemistry.
• Definition of period of drugs validity is based
  on methods of analytical chemistry.

16
Chemical analysis and its varieties

• Elemental analysis
• Function analysis
• Molecular analysis
• Phase analysis
• Diffraction analysis

17

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

18

• Function analysis is the analysis which answer
  what functional groups are contained in
  investigated substance
• Methods of the molecular analysis receive the
  information about substances which consist of
  molecules or formular parts.

19

• Phase analysis detection and definition of
  different phases (solid, liquid, gas), which are
  contained in the investigated system.
• Diffraction analysis determines the crystal
  lattice structure containing atoms, molecules and
  ions.

20
Pharmaceutical analysis is determination of drug
quality (manufactured or pharmacy compounded)

• Pharmaceutical analysis includes
• analysis of drugs
• analysis of medicinal herbs
• process monitoring of drugs
• toxicological analysis
• judicial-chemical analysis

21
IUPAC Classification of analytical methods in
accordance with mass and volume of analytic sample
Method name Mass of sample, g Volume of sample, ml
Gramm-method 110 10100
Cantigramm-method 0,050,5 110
Milligramm-method 10-60,001 10-40,1
Microgramm-method 10-910-6 10-610-4
Nanogramm-method 10-1210-9 10-1010-7
Picogramm-method 10-12 10-10
22
(No Transcript)
23

• The signal which bears the information on
  elementary objects, is called as an analytical
  signal. The analytical signal can be the
  carrier for both qualitative and quantitative
  information.
• Sensitivity of analytical reaction is the least
  amount of substance, which can be detected with
  the reagent in one drop of solution.

24

• The sensitivity express to next correlated
  values
• Limit of detection Determined minimum (m) the
  least amount of substance, which present in
  analysed solution and can be detected with the
  reagent. Calculated in ?g. 1 ?g 0,000001 g.
• Limit of concentration Minimal concentration
  (Cmin) the least concentration of substance in
  the solution which still can be detected in small
  portion or volume of analysed solution.

25

• Maximum of dilution (W 1/Cmin) quantity (ml)
  of solution, containing 1 g of the analysed
  substance, which can be detected with a definite
  reaction (reagent).
• Analytical reaction is considered more sensitive
  under conditions when determined minimum and
  minimal concentration of analyzed solution are
  low and maximum of dilution is high.

26
2. Main principles of theory of strong
electrolytes.

• activity (?) effective concentration of ions in
  solution, when it reacts

27
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 DebyeHückel theory

28
To calculate activity coefficients use the
DebyeHückel equation

• if ? ? 0,01
• if ? ? 0,1
• if ? ? 1,0

29
Experimentally is possible to find only the Mean
activity coefficient

• for binary electrolyte AB
• for electrolyte structure AmBn

30
Mean activity coefficient may be calculated
theoretically by using DebyeHückel equation

• if ? ? 0,01
• if ? ? 0,1
• if ? ?1,0.

31
For simplification of calculations of activity
coefficients use these assumptions

• 1. Activity coefficients of ions with identical
  charge irrespective of ions radius are
  approximately equal.
• 2. Activity coefficients of neutral parts in
  dilute solutions of electrolytes equals 1.
• 3. Very dilute solutions of electrolytes are
  possible to consider ideal.

32
3. The Law of Mass Action in Analytical Chemistry.

• Concentrational (real) constant of chemical
  equilibrium
• nA mB ? lC pD
• p-function of constant equilibrium
• pK lgK.

33
?? thermodynamic equilibrium constant (it
depends on temperature and pressure)

• where f activity coefficient
• We use KR, when we have real conditions
  (influence of ionic strength, temperature and
  pressure)

34

• ?C conditional equilibrium constant
• where C formality, is a substances total
  concentration in solution regardless of its
  specific chemical form.
• where ? - parts per mol

35

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

36

• 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 acids
  (bases) initial concentration, CHA.
• H2S ? H HS-
• HS- ? H S2-
• CS S2 HS H2S.

37

• 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 Mzi and Azj 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
38
Main types of chemical reactions which are used
in analytical chemistry

• Acid-base reaction (the reaction of an acid with
  a base)
• CH3COOH(aq) NH3(aq) ? CH3COO(aq) NH4(aq)
• A precipitation reaction occurs when two or more
  soluble species combine to form an insoluble
  product.
• Pb2(aq) 2Cl(aq) ? PbCl2(s)

39

• reaction between the metal ion and the ligand is
  typical of a complexation reaction.
• Cd2(aq) 4(NH3)(aq) ? Cd(NH3)42(aq)
• redox reaction - an electron-transfer reaction.
• 2Fe3(aq) H2C2O4(aq) 2H2O(l) ? 2Fe2(aq)
  2CO2(g) 2H3O(aq)

40
(No Transcript)
41
4. Bronsted-Lowry theory of acids and bases.

• A substance, that dissolves in water to give an
  electrically conducting solution is called an
  electrolyte.
• A substance, that dissolves in water to give
  nonconducting or very poorly conducting solution
  is called a nonelectrolyte.

42

• According to Svante Arrhenius concept
• Acid is any substance that, when dissolved in
  water, increase the concentration of hydrogen ion
  H.
• Base is any substance that, when dissolved in
  water, increase the concentration of hydroxide
  ion OH.
• NaOH ? Na OH
• HCl ? H Cl

43
A useful definition of acids and bases was
indepen-dently introduced by Johannes Brønsted
(18791947) and Thomas Lowry (18741936) in 1923.

• acids are proton donors
• bases are proton acceptors
• Acid ? Base ?

44
Constant reaction of a dissociation solvent has
equation

• Autoprotolysis constant of solvent is product of
  activity lyonium and lyate

45
Neutrality of solution determines activity of
lyonium and lyate ?ons

• Condition of neutrality

46
?? of some solvents
Solvent Limits ??
H2SO4 0 3,6
HCOOH 0 6,70
H2O 0-14
CH3COOH 0 14,4
CH3OH 0 17,3
acetone 0 21,1
Solvent Limits ??
C2H5OH 0 19,00
CH3 C ? N 0 19,00
liquid ammonia 0 22,0
FMA 0 17,0
DMFA 0 18,0
47
The Brønsted-Lowry concept of acids and bases has
greater scope than the Arrhenius concept

• the general description of acid-base reaction
• possibility a quantitative estimation strength of
  acid and base
• ?? ?2? ? ?3? ?
• B H2O ? BH OH

48
Solvents

• progenic (A species that can serve as a proton
  donor)
• protophilic (A species that can serve as a proton
  acceptor)
• amphiprotic (A species that can serve as both a
  proton donor and a proton acceptor)
• aprotic (A species that cant serve a proton)

49

• proton acceptors properties increase ?
• H2SO4 CCl3COOH CH3COOH H2O C2H5OH NH3
  C5H5N
• proton donors properties increase ?

50
Thanks for your attention!