Analytical Chemistry. A Qualitative & Quantitative Approach

244 Pages·2015·2.236 MB·english

by  Deepak Chowrasia, Nisha Sharma

Analytical Chemistry
A Qualitative
&
Quantitative Approach

(General Techniques)

Deepak Chowrasia Dr. Nisha Sharma

Assistant Professor Head of Department
Institute of Pharmacy Institute of Pharmacy
CSJM University, Kanpur, (U.P.), India CSJM University, Kanpur, (U.P.), India
Analytical Chemistry-A Qualitative & Quantitative Approach, (General Techniques) i
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Analytical Chemistry-A Qualitative & Quantitative Approach, (General Techniques) ii
Preface for First Edition
It is difficult to pen down feeling on publication of my book “Analytical Chemistry-A
Qualitative & Quantitative Approach, (General Techniques). The idea of writing
book of this magnitude was encompasses from my own experience & vision while
critically analyzing students of science (B.Sc/M.Sc/Pharmacy/B.Tech.) getting
difficulties in searching book predominately in the field of “Analytical Chemistry”
although the market is surplus with vast majority of books dealing directly or indirectly
under same heading, but their high technical standard, non-soothing language, irrelevant
to topic, non-specific course description, lengthy chapters, and insufficient illustration
ultimately limits their student friendly applicability. This book thus obscure out all the
difficulties a student find in their academic career. While writing this book, an intensive
care has been taken to present each chapter in a “lay-man-lucid-language (LML) yet not
to be get devoid from technical track. A useful categorization of each chapter into
section & sub-section renders any jumbling of topics, at the same time maintaining their
technical including conceptual background and adhere reader to the main stream at no
loss of interest in the subject. The book is enriched with numerous illustrative diagrams,
concise tabulation of data, minute details, exercise, and multiple choice questions which
are important not only from the point of view of student internal & external
examination, but also beneficial for their competitive examination
(GATE/GPAT/CSIR-NET).
In the last, I express my worthy thanks & a great success to all academicians,
researchers, and students for their bright future.
-Deepak Chowrasia
Analytical Chemistry-A Qualitative & Quantitative Approach, (General Techniques) v
Table of Content
Chapter Page
Title Author/s
Nos. Nos.
01 Non Aqueous Titration Deepak Chowrasia 1
02 Complexometric Titration Deepak Chowrasia 27
Dr. Nisha Sharma,
03 Karl Fischer Titration 51
Deepak Chowrasia
Deepak Chowrasia,
04 Diazotization Titration 61
Ajay Kumar
Dr. Nisha Sharma,
05 Kjeldhal Titration 71
Deepak Chowrasia
06 Paper Chromatography Deepak Chowrasia, 81
07 Thin Layer Chromatography Deepak Chowrasia 99
08 Column Chromatography Deepak Chowrasia 115
09 HPLC Deepak Chowrasia 131
10 Gas Chromatography Deepak Chowrasia 155
11 Ion Exchange Chromatography Deepak Chowrasia 195
12 Size Exclusion Chromatography Deepak Chowrasia 209
Dr. Nisha Sharma,
13 Conductometry 219
Deepak Chowrasia
14 Coulometry Deepak Chowrasia 237
15 Potentiometry Deepak Chowrasia 247
Chapter - 01
NON AQUEOUS TITRATION
- Deepak Chowrasia

Chowrasia, Deepak NON AQUEOUS TITRATION
Analytical Chemistry-A Qualitative & Quantitative Approach, (General Techniques) 3
NON AQUEOUS TITRATION
(Chapter Overview)

01. INTRODUCTION ...................................................................................................................... 5
02. THEORY...................................................................................................................................... 5
03. ADVANTAGES OF NON AQUEOUS TITRATIONS ..................................................... 6
04. LIMITATIONS OF NON-AQUEOUS TITRATIONS ..................................................... 6
05. NON AQUEOUS SOLVENTS-PROPERTIES AND PROBLEMS ............................... 6
06. NON-AQUEOUS SOLVENTS; CLASSIFICATION ....................................................... 7
06.A. Aprotic or neutral solvents ........................................................................................... 7
06.B. Protophilic solvent/proton loving solvent ................................................................. 7
06.C. Protogenic solvent .......................................................................................................... 8
06.D. Amphiprotic solvent ....................................................................................................... 8
07. EFFECT OF HEAT ON NON-AQUEOUS TITRATION ............................................... 9
08. END POINT DETECTION IN NON-AQUEOUS TITRATION .................................... 9
08.A. Visual method .................................................................................................................. 9
08.B Instrumental method ................................................................................................... 10
09. APPARATUS ............................................................................................................................ 10
10. GENERAL PROCEDURE OF NON-AQUEOUS TITRATIONS ............................... 11
11. PRECAUTIONS DURING TITRATION .......................................................................... 11
12. METHODS IN NON-AQUEOUS TITRATION............................................................... 12
12.A. Acidimetric analysis in non-aqueous titrations ..................................................... 12
12.A.1. Titrant for acidimetric non-aqueous analysis .............................................. 12
12.A.1.a. Preparation of acetous 0.1 M perchloric acid solution ............. 12
12.A.1.a.1. Standardization of acetous 0.1M perchloric acid . 13
12.A.1.b. Preparation of 0.1 M perchloric acid solution in dioxane ........ 13
12.A.1.b.1. Standardization of 0.1M perchloric acid solution
in dioxane ...................................................................................... 13
12.A.2. Types of Acidimetric analysis in non aqueous titrations .......................... 13
12.A.2.1. Titration of amines and amines salts of organic acid ................ 13
12.A.2.2. Titration of halogen acid salt of bases ......................................... 13
12.A.2.3. Assay of few basic chemicals by acidimetric non aqueous
titration ........................................................................................................... 14
Chowrasia, Deepak NON AQUEOUS TITRATION
Analytical Chemistry-A Qualitative & Quantitative Approach, (General Techniques) 4
12.A.2.3.1. Assay of Ephedrine HCl ............................................ 14
12.A.2.3.2. Assay of adrenaline: .................................................. 14
12.A.2.3.3. Assay of Sodium Saccharine ..................................... 14
12.B. Alkalimetric analysis in non aqueous titration ...................................................... 15
12.B.1. Titrant used in alkalimetric analysis in non aqueous titrations ............. 15
12.B.1.a. Preparation of 0.1 M tetrabutylammonium hydroxide in
Toluene-Methanol. ........................................................................................... 15
12.B.1.a.1 Standardization of 0.1 M tetrabutylammonium
hydroxide ...................................................................................... 16
12.B.1.b. Preparation of 0.1M Potassium methoxide in toluene-
methanol ........................................................................................................... 16
12.B.1.b.1. Standardization of 0.1 M Potassium methoxide in
toluene-methanol ............................................................................. 16
12.B.1.c. Preparation of 0.1M lithium methoxide in toluene-methanol ... 16
12.B.1.c.1. Standardization of 0.1 M lithium methoxide in
toluene-methanol ............................................................................. 16
12.B.2. Assay of few acidic chemicals by alkalimetric non aqueous titration .... 17
12.B.2.a. Assay of Ethosuximide .................................................................... 17
12.B.2.b. Assay of benzoic acid ..................................................................... 17
12.B.2.c. Assay of chlorthalidone .................................................................. 17
13. APPLICATIONS OF NON-AQUEOUS TITRATION ................................................... 17
14. EXERCISE ................................................................................................................................ 19
15. MULTIPLE CHOICE QUESTIONS .................................................................................. 20

Chowrasia, Deepak NON AQUEOUS TITRATION
Analytical Chemistry-A Qualitative & Quantitative Approach, (General Techniques) 5
NON AQUEOUS TITRATIONS

01. INTRODUCTION
Non aqueous titrations provide a versatile platform for titrating complex organic molecules
including therapeutic important pharmaceuticals (please refer table 05) as well as chemical
compounds that possess problem of low solubility and high ionization in aqueous solvents.
Also the weakly acidic or weakly basic substances, as most of the therapeutic chemical
moieties, that are unable to give sharpe end point in aqueous solvent are far better titrated in
non aqueous titration with good equivalence point as their strength is enhanced by dissolving
them in suitable non aqueous solvents like carbon tetrachloride, benzene or liquid ammonia
etc.
02. THEORY
Numerous efforts had been made by different workers in order to justify & establish a unified
universal theory regarding acid and bases (see table 01). The Lowery-Bronsted concept
(1923) of acid and base can be parallely and equally well imposed to acid base titrations, both
in aqueous and non aqueous solvents. Accordingly, acids are the substance that has tendency
to donate a proton while base is a substance having tendency to accept proton. Shortly, acids
are proton donor while bases are proton acceptor.
S.No. Concept Acid Property Base Property
01 Oldest concept Hydrogen or oxygen Bitter in taste, turn litmus
containing substance, Sour in blue
taste, turn litmus red
02 Arrhenius concept Proton donor in aqueous Proton acceptor in aqueous
solution solution
03 Lewis theory Electron pair acceptor Electron pair donor

04 Usanovich concept Accept anion or donate cation Donate anion or accept cation

05 Lux-flood concept Oxide ion acceptor Oxide ion donor
Table 01: Concept of Acid & Base
Let us consider dissociation of acid PB in a solution which gives proton P and conjugate base
B.
PB P+ + B-
acid Proton conjugated base

Likewise a base B can unite with proton P to yield conjugated acid PB
Chowrasia, Deepak NON AQUEOUS TITRATION
Analytical Chemistry-A Qualitative & Quantitative Approach, (General Techniques) 6
PB
B + P+
Base

Further expanding the above definition, acid is either an electrically neutral molecule like HCl
or HNO or a positive charge cation like C H NH + on other hand base is an electrically
3 6 5 3
neutral molecule like C H NH or negative charged anions like Cl-, NO -.
6 5 2 3
03. ADVANTAGES OF NON AQUEOUS TITRATIONS
A. Simple, handy, accurate, precise, and rapid technique compare to classical method
of analysis.
B. Titration of chemicals which shows poor end point in aqueous titrations.
C. Poor water soluble substance can be easily and accurately titrated
D. Improves reactivity of low or poor reactive substances (weak acids and bases).
E. Instant availability of result.
F. Requires no special or costlier apparatus.
G. Visual detection of end point mostly (except very concentrated or highly coloured
solution where potentiometric end point determination has to be done).

04. LIMITATIONS OF NON-AQUEOUS TITRATIONS
A. Utilization of costlier and toxic organic solvents.
B. No recovery of solvent at the end of titration.
C. Moisture content should be less than 0.05% during overall process of titration.
D. Difficulty in determining visual detection of end point in highly colored solution.
E. Required skills for performing titrations.

05. NON AQUEOUS SOLVENTS-PROPERTIES AND PROBLEMS
Organic solvents like glacial acetic acid, dioxane, acetonitrile are only the few names among
the wide variety of solvents that are used efficiently and effectively in non aqueous titrations.
An ideal non aqueous solvent (did we have?) must possess properties of strict purity,
analytical grade, economicity, non reactive, non toxic, dry (water free/anhydrous), good
solubility, recyclibility, eco-friendly (tough to achieved due to their organic characteristic)
and free from property of interfering with detection of end point. Non aqueous solvents have a
unique property of equalizing the strength of weak acidic or weak basic substances to that of
strong acidic and strong basic substances and thus this property of solvent equalization is
termed as leveling or solvent effect of non aqueous solvents. It is advisable to protect solvent
(non aqueous) from exposure to atmospheric air and titration must be performed in closed
vessel to render the interference caused by moisture. Since all non aqueous solvents have
Chowrasia, Deepak NON AQUEOUS TITRATION
Analytical Chemistry-A Qualitative & Quantitative Approach, (General Techniques) 7
higher value of thermal coefficient of expansion (change in physical property w.r.t. to
temperature) compare to water-an aqueous solvent, hence it is recommended to store them at
constant temperature and titration must be performed at same temperature to minimized error.
06. NON-AQUEOUS SOLVENTS; CLASSIFICATION
Non aqueous solvents are capable of donating and accepting proton under condition of
titration, depending upon their nature of donating or accepting protons they are classified as
06.A. Aprotic solvents
06.B. Protophilic solvent
06.C. Protogenic solvents
06.D. Amphiprotic solvents
06.A. Aprotic or neutral solvents
These solvent posses a universal characteristic of beings non reactive, non ionizing, low
dielectric constant (see table 02), and are neutral in nature. They are unable to generate proton
under titrimetric condition and do not take part in overall chemical reaction because of their,
this property, they are extensively used for diluting reaction mixtures. For example toluene
and carbon tetrachloride.
Non aqueous solvents Dielectric constant
Acetic acid 6.15
Benzene 2.27
Chloroform 4.81
Dioxane 2.21
Acetonitrile 37.5
Sulphuric acid 100
Water* 81
Table 02: Dielectric constant of some solvents
06.B. Protophilic solvent/proton loving solvent
These solvents (acetone, ammonia, ether, dioxane, amines-hydrazine, ethylenediamine) have
high tendency to accept or gain protons during titration. They are basic in nature and readily
react with acid to yield solvated protons. Protophilic solvents like pyridine, ethylenediamine,
n-butylamine give high blank titration value due to absorption of atmospheric carbon dioxide
hence it is necessary to kept them in tightly closed Pyrex glass containers.
Chowrasia, Deepak NON AQUEOUS TITRATIONS