APA S1 GOKULRAJ POTENTIOMETRIC TITRATION.pptx

POTENTIOMETRIC TITRATION
Submitted To:
DR. C. SREEDHAR
PROFESSOR AND HOD
DEPT. OF PHARMACEUTICAL
ANALYSIS
KARNATAKA COLLEGE OF PHARMACY
BANGALORE
SUBMITTED BY:
S.GOKULRAJ
M PHARM 1ST SEMESTER
DEPT.OF PHARMACEUTICAL
ANALYSIS
KARNATAKA COLLEGE OF
PHARMACY
1
SUBJECT: APA

content
 Introduction
 Principle
 Nernst equation
 Components of potentiometric cell
 Types of electrode
 Potentiometric titration
 Instrumentation
 Types of potentiometric titration
 Advantages of potentiometri titration
 Application of potentiometric titration
2

INTRODUCTION
 It is consists of measuring the potential or emf of a
solution using set of indicator and reference
electrode.
 It is based on potential measurement of
electrochemical cells without any appreciable current.
 The use of electrodes to measure voltages from
chemical reactions.
 The potential of a solution depends on the nature and
concentration of the ions of the drug absorption.
 The potential is measured in mV using a
potentiometer.
3

PRICIPLE
 The principle is based on the fact that the potential of the
given sample is directly proportional to the concentration
of its electroactive ions.
 In the potentiometry is when the pair of electrode is
placed in the sample solution it shows the potential
differences by the addition of the titrant.
4

NERNST EQUATION
 The potential (E) of a metal electrode at 25°C
Immersed into a solution of it’s own ions is given by,
E=E°+(0.0592/n) log c
 Where,
• E- potential
• E°-standard potential of the metal
• n- valency of ions
• C-concentration of ions
5

Components of potentiometric cell:
 They are four type of components are used they are,
1. Reference electrode
2. Salt bridge
3. Analyte
4. Indicator electrode
E cell = E reference +E junction + E indicator
6

TYPES OF ELECTRODE
 The electrodes are mainly used to measure the voltages.
 They are two different types of electrodes used they are,
1. Reference electrode
2. Indicator electrode
1. Reference electrode:
 It is the one which has a standard potential on its own and it’s
potential does not change to whichever solution it is dipped into.
 Different types of reference electrodes used they are,
1. Hydrogen electrode
2. Saturated calomel electrode
3. Silver-silver chloride electrode
4. Mercury-mercurous sulphate electrode
5. Mercury-Mercuric Oxide Electrode:
7

1. Hydrogen electrode:
 It will be used as indicator as well as reference
electrode.
 It consists of platinum foil coated with platinum black and
has wire contact through the mercury.
 This assembly is enclosed in a glass covering through
which hydrogen is passed at 1 atmospheric pressure
continuously and dipped into the solution of standard
acid or unknown solution.
8

2. Saturated calomel electrode:
 It consists of an inner jacket and outer
sleeve.
 The inner tube has wire contact with
mercury and plugged with a mixture of
calomel and KCL.
 This is surrounded by an outer sleeve
and the tip is filled with crystals of KCL
and porous plug of asbestos.
 The space between the inner jacket and
outer sleeve is filled with either saturated
KCL or 1N KCL or 0.1N KCL, on the
potential of the electrode depends upon.
 The potential of the half cell depends
upon
 Concentration of the potassium chloride
used.
9

3.Silver-silver chloride electrode:
 It is simply a silver wire coated electrolyticaly with silver
chloride and dipped into potassium chloride.
 The potential of this half cell also depends upon
temperature as well as concentration of potassium
chloride used.
10

2.Indicator electrode:
 It is responds to changes in emf or pH of a solution.
 It is used to indicate the emf or potential or pH of a
solution.
 Different types of indicator electrodes used they are,
1. Antimony –antimony oxide electrode
2. Hydrogen electrode
3. Glass electrode
1.Hydrogen electrode:
 It is used as indicator electrode when dipped into a
unknown
Solution whose potential or pH has to be determined.
11

2.Antimony-antimony oxide electrode:
 It consists of a antimony rod dipped into a solution,
whose potential or PH has to be determined.
 The antimony react with water to form antimony oxide
and release the electrons.
Sb+H2O SBO+2H+3e
12

3.Glass electrode:
 It is the most widely used in the indicator electrode.
 It is selective and response to change in the concentration of
hydrogen ion.
 The glass electrode consists of the glass tube with a thin PH
sensitive glass bulb at its tip.
 It has a silver-silver chloride wire at the center of the tube and the
lower tip of the wire immerses into the 0.1N HCL filled in the glass
tube.
 This assembly act as an indicator electrode and is dipped into a
solution whose PH or potential to be known.
 The potential of the glass electrode is given by,
E=K+0.0592(PH1-PH2)at 25C
13

Potentiometric titration
 These are the titration in which the end point of
titration can be determined by measuring the
potential or changes in the potential of a solution
caused by the addition of titrant.
 Alternatively the PH can also be monitored during
the titration to detect end point.
 In a titration, the addition of titrant cause changes
in the concentration or activity of ions in solution.
14

Instrumentation
 Titration can be done manually or under
automation.
 When it is done manually, a beaker with a stirrer
and a pipette are sufficient.
 Incase of automatic models,a sample cell which
can hold a pair of electrode,inlet for titrant and a
stirrer for mixing a solution are essential.
 The pair of reference and indicator electrode
depends on the type of titration.
15

 A= reference
electrode
 B= indicator electrode
 C=burette
 D=PH meter with a
mV scale
 E=magnetic stirrer
with variable speed
 F= magnetic guide
Process of instrumentation:
16

Types of potentiometric titrations
 They are different types,
1. Acid - base titrations
2. Redox titrations
3. Diazotisation titrations
4. Complexometric titrations
5. Precipitation titrations
6. Non aquous titrations
17

1. Acid – Base titrations:
 The acid – base titrations can be done in aqueous as
well as by non-aqueous medium.
 Reference electrode : Saturated calomel electrode
 Indicator electrode : Glass electrode
Examples:
 Titration of HCL vs NAOH
 Titration of HCL vs NH4OH
 Titration of CH3COOH vs NH4OH
 Titration of CH3COOH vs NAOH
 Titration of (CH3COOH+HCL )vs NAOH
 Titration of (NH4OH+NAOH )vs HCL etc….
18

2.Redox titration:
 In this titration will be an a oxidation and reduction
process is happened.
 Reference electrode: saturated calomel electrode (or)
silver- silver chloride
electrode.
 Indicator electrode: platinum wire or foil
Exampls:
 Ferrous ammonium sulphate in dil.H2SO4 (VS) KMNO4
 Ferrous ammonium sulphate in dil.H2SO4 (VS) K2Cr2O7
 Ferrous sulphate in 6N H2SO4 (VS) cerric ammonium
sulphate
Ce+4 + Fe+2 → Ce+3 + Fe+3
19

3.Complexometric titration:
 In this method of titration used to determine the metal
ions by using a potentiometric titration method.
 Reference electrode: saturated calomel electrode
 Indicator electrode: silver-silver chloride electrode (or)
mercury electrode
Examples
 Divalent ions,trivalent ions,CN etc… (vs) EDTA.
Ag+ + 2 CN- → [Ag(CN)2]- (chemically stable )
20

4.Precipitation titration:
 For the quantitative determination of several ions or
elements,precipitating agents are used as titrants and the
end point is determined by potentiometric method.
 Reference electrode: saturated calomel electrode (or)
silver-silver chloride
electrode(or)
hydrogen electrode
 Indicator electrode: silver wire electrode
Examples:
 Determination of halogen by using silver nitrate.
 The titrant mixture of Cl and Br and I with AgNO3.
AgN03 + KCl → AgCl ↓ + KNO3
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5.DIAZOTATION TITRATION:
 The formation of diazonium salt is called as a diazotation
titration.
 It is detect by two methods they are,
1. One method is detect by using starch iodide paper
(external indicator method).
2. The other method, better than the external indicator
method is by potentiometric method of determining end
point.
 Reference electrode: Saturated calomel electrode
 Indicator electrode: Glass electrode
Examples:
 Alkaloids,amines,sulpha drugs and other drugs which
contain aromatic primary amino group can be titrated
against 0.1N sodium nitrate in HCL.
22

Assay of nitrazepam
 Material required:
0.25g of nitrazepam,25ml of acetic anhydride,250ml of 0.1M perchloric acid,a
potentiometer,a magnatic stirrer,burette.
 Theory:
It is weakly basic compound and hence,it may be titrated conveniently by means
of a non-aqueous titration technique and determining the end point potentiometrically.
 Procedure:
weigh accurately 0.25g of nitrazepam and dissolve in 25ml of acetic anhydride.titrate
with 0.1M perchloric acid placed in a burette and adding it carefully into the beaker
kept on a magnetic stirrer potentiometrically.
 Each ml of 0.1M perchloric acid is equvalent to 28.13 mg of C15H11N3O3
23

TITRATION
 Potentiometric titrations is employed for acid-base,
redox, neutralization, precipitation,diazotation
titration and complexometric reactions.
 The method can be used for coloured solution.
 Apparatus are not more expensive and It is freely
available.
 There is no need of external indicator for redox
titrations.
 It is employed for the analysis of dilute solutions with
high degree of accuracy.
 The technique is applicable even in non-aqueous
media.
 Rapid analysis method.
 Possibility of automation of titration processes.
 High sensitivity.
24

APPLICATIONS
 Clinical chemistry:
 Ion selective electrodes are present sensors for clinical samples
because of their selectivity for analyte in complex matrices.
 The most common analytes are electrolytes such as Na, k,Ca,H, and Cl
and dissolved gases such as CO₂
 Environmental chemistry:
For analysis of CN,NH, NO, F, in water and waste water.
 Potentiometric titrations:
 For determining the equivalence point of an acid base titration.
 possible for redox, precipitation, acid-base, complexation as well as for
all titrations in aqueous n non aqueous solvents.
 Agriculture:
NO3,NH4,I,Ca, K,CN, Cl in soils, plant materials, feed stuffs,
fertilizers.
 Detergent manufacturing:
Ca, Ba, F for studying effects in water quality.
25

 Food processing:
 Salt content of meat fish dairy products fruit juices brewing
solutions
 Ca in dairy products and beer
 K in fruit juice and wine making
 Corrosive effects of NO3 in canned foods
 F in drinking water and other drinks
 NO3 and NO2 in meat preservatives
 It is widely used electro-analytical method.
 Potentiometric principle is useful in checking the pH of the
official buffers & different test solutions.
 Assay of bisacodyl suppositories and assay of sulpha drugs
can be estimated potentiometrically.
 A no. of drugs official in pharmacopoeia are assayed by this
procedure, some of them are Caffeine, Phenobarbitol,
Tetrahydrazine HCl, Amoxyllin sodium, Disulfuram,
Hydrallazine HCl, Metaclopramide HCl, Propranolol HCI,
Nalixidic acid, Lomustine,etc…
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Reference
 Text book of PHARMACEUTICAL ANALYSIS 4th
edition Dr. Ravi Sankar.
 Text book of pharmaceutical drug analysis 3rd
edition Dr. ASHUTOSH KAR
 Instrumental method of chemical analysis
Dr. R.Chatwal
27

THANK YOU
28

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