Advanced Techniques of Analytical Chemistry: Volume 1

By Anju Goyal and Harish Kumar

Advanced Techniques of Analytical Chemistry explains analytical chemistry in an accessible manner for students. The book provides basic and practical knowledge that helps the learner to understand the methods used in conducting experiments. Readers will understand the key concepts of qualitative and quantitative analysis through easy-to-read chapters written for chemistry students.Volume 1 covers the topic of volumetric analysis in detail. Topic-wise chapters introduce the reader to volumetric titrations and then explain the range of titration techniques which include aqueous acid-base titration, non-aqueous titration, redox titration, complexometric titration and some miscellaneous methods like diazotisation titration, Kjeldahl’s method and the oxygen flask combustion method.The combination of basic and advanced methods makes this an ideal textbook for chemistry students at graduate and undergraduate levels as well as an ideal handbook for the laboratory instructor.

• Language: English
• Publisher: Bentham Science Publishers
• Release date: Feb 25, 2022
• ISBN: 9789815050233

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Introduction to Analytical Chemistry

Sapna Kumari¹, *, Anju Goyal¹, Madhukar Garg¹, Harish Verma²

¹ Chitkara College of Pharmacy, Chitkara University, Punjab, India

² Govt College of Pharmacy, Rohru, Shimla, Himachal Pradesh, India

Abstract

Analytical chemistry, a branch of chemistry, deals with the analysis of substances. Identification of the constituents from the mixture or substance is called qualitative analysis while Quantitative Analysis deals with determining the purity of the constituents present in the mixture. This is also known as assay method. Various methods like volumetric analysis, gravimetric analysis, polarimetry, refractometry, photometry, fluorimetry, electrochemical methods, chromatographic methods and biological methods comes under the category of quantitative analysis. Volumetric titrations are the elementary procedures applied in the life sciences, pharmaceutics, industrial analysis, water pollution and clinical chemistry and are used to determine the amount of analyte with the standard solution. Main advantages of these methods are cost-effective, rapid and simple, while disadvantages include pH, temperature, and humidity sensitivity, indicator requirement, occurrence of human error, etc.

Keywords: Analytical chemistry, Endpoint, Indicator, Quantitative analysis, Volumetric titration.

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* Corresponding Author Sapna Kumari: Chitkara College of Pharmacy, Chitkara University, Punjab, India; Email: [e-mail]

INTRODUCTION

Analytical chemistry is the branch of chemistry which deals with the analysis of substances. It is mainly divided into two categories:

(1) Qualitative Analysis

(2) Quantitative Analysis

Qualitative analysis is primarily concerned with the identification of the constituents present in a chemical substance or a mixture of substances.

Quantitative analysis is also primarily concerned with the exact determination of the purity of the number of constituents present in a chemical substance or a mixture of substances.

Quantitative analysis is carried out mainly for determining the purity of chemical substances. The method used for the determination of purity is called the assay method. There are many methods of quantitative analysis such as volumetric analysis, gravimetric analysis, polarimetry, refractometry, photometry, fluori-metry, electrochemical methods, chromatographic methods, and biological methods.

Volumetric analysis is also known as titrimetric analysis which is carried out in a routine manner and hence is discussed here [1].

INTRODUCTION TO VOLUMETRIC TITRATIONS

Volumetric titrations are the basic techniques in chemistry that are applied in the life sciences, pharmaceutics, industrial analysis, water pollution, and clinical chemistry. Volumetric titrations or titrimetric analysis are the quantitative analytical procedures that are used to determine the amount of analyte with the standard solution. In this titration, the standard solution has been added gradually to the sample containing an unknown concentration of reactant until reactant is consumed (stochiometric completion). This is called equivalence point [2]. Indicators have been used to identify the endpoint. Popularly, these titrations are used in acid-base reactions.

The first method of Volumetric Analysis was devised and found by the French chemist Jean-Baptiste-Andre-Dumas as he was trying to determine the proportion of nitrogen combined with other elements in organic compounds. To ensure the conversion of the nitrogen compound into pure gas, the nitrogen compound was burnt in a furnace and passed along a furnace in a stream of carbon dioxide that is passed into a strong alkali solution. The mass of the nitrogen is calculated and occupied under known conditions of pressure and volume from the sample.

Advantages And Disadvantages Of Volumetric Analysis

Titration is a method used to determine the concentration of an unknown sample solution by a recognized concentration of solute. The titrimetric method includes three types: volumetric, gravimetric, and coulometric titrimetric. The volumetric titration was used to determine the volume of solution with the known concentration involving a quantitative reaction with a substance solution to be analysed.

The Advantages of Volumetric Titration are as Follows:

The major advantage of volumetric titration is that it is a simple and cost-effective method.

Volumetric titration is not sophisticated, so skill is not required to handle it.

The volumetric titration is rapid and gives accurate results.

It is a simple method compared to other types of titrations.

The reaction can identify visually at equilibrium or endpoint.

The Disadvantages of Volumetric Titration are as Follows:

Certain factors such as pH, temperature, and humidity may affect the titration results, as this is an open system.

Human error may occur during processing and may affect accuracy.

It requires an indicator for the reactions to occur.

The major disadvantage of volumetric titration is that this can produce large volumes of chemical waste and that needs to be disposed of it.

It requires reactions occurring in a liquid phase.

What is Titration?

This is a basic laboratory method of quantitative chemical analysis used to determine the unknown concentration of a known reactant. In this method, volume measurements play a key role in titration, also known as volumetric analysis (Fig. 1). A reagent called the titrant or titrator of a known concentration (a standard solution) and volume is used to react with a solution of the analyte or titrant whose concentration is not known [3, 4]. Using a calibrated burette or chemistry pipetting syringe to add the titrant.

Fig. (1))

Representing assembly of procedure of titration.

Simple Titrations

Simple titration aims to find the concentration of an unknown solution with the help of the known concentration of another solution (Fig. 2).

Fig. (2))

Illustrating volumetric titrations.

The Volumetric Analysis is Divided into the Following Types:

Let us take a solution of a substance ‘A’ of unknown concentration. We are provided with a solution of another substance ‘B’ whose concentration is known (N1). We take a certain known volume (V2 liters) of ‘A’ in a flask and start adding ‘B’ from the burette to ‘A’ slowly till all the ‘A’ is consumed by ‘B’. This can be known with the aid of a suitable indicator, which shows colour change after the complete consumption of ‘A’. Let the volume of B consumed be V1 liter According to the law of equivalents, the number of equivalents of ‘A’ would be equal to the number of equivalents of ‘B’.

Hence

where N2 is the concentration of ‘A’.

Thus, using this equation, the value of N2 can be calculated.

There are four types of simple titration, namely.

Acid-base titrations

Redox titrations

Precipitation titrations and

Complexometric titrations

Types of Volumetric Titrations

There are various sorts of titrations whose goals are different from the others. The most common types of titrations in qualitative work are acid-base titrations, redox titrations, complexometric titration and precipitation titration (Fig.