Titration definition and much more
Know How
Guide

Basics of Titration - A widely used quantitative analytical technique

Know How
Guide

Titration is an analytical technique which allows the quantitative determination of a specific substance dissolved in a sample. With this handbook you will learn more than just the titration definition.

This booklet is intended as a first introduction to theory and practice of titration.
This booklet is intended as a first introduction to theory and practice of titration.

This handbook focuses on giving a clear introduction of titration.

The basic knowledge that is needed to understand titration is given, different kinds of titration types are illustrated and evaluation principles explained. Special attention is given to supply all the necessary information needed to perform titration correctly so as to produce reliable data. Finally, a brief introduction to chemistry relevant to titration is explained.

This handbook covers the following topics and more:

  • Titration definition
  • Titration theory
  • Automated titrators
  • Quality management in titration
  • Titer determination
  • Chemical backgrounds (the mole, reaction stoichiometry , etc)
  • Glossary (titration, titer, titrant, indication, analyte, etc)
Download the handbook to learn everything about the basics of titration. You will find valuable basic information about this widely used technique.

1. Definition of titration

Titration is an analytical technique which allows the quantitative determination of a specific substance (analyte) dissolved in a sample. It is based on a complete chemical reaction between the analyte and a reagent (titrant) of known concentration which is added to the sample. A well-known example is the titration of acetic acid (CH3COOH) in vinegar with sodium hydroxide, NaOH:

CH3COOH + NaOH → CH3COO- + Na+ + H2O

Analyte        Reagent        Reaction Products

 

The titrant is added until the reaction is complete. In order to be suitable for a determination the end of the titration reaction has to be easily observable. This means that the reaction has to be monitored (indicated) by appropriate techniques, e.g. potentiometry (potential measurement with a sensor) or with colour indicators.
The measurement of the dispensed titrant volume allows the calculation of the analyte content based on the stoichiometry of the chemical reaction. The reaction involved in a titration must be fast, complete, unambiguous and observable.

 

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2. Historical development

The classical way

Titration is a classical analytical technique widely used. Originally, it was performed by adding the titrant using a graduated glass cylinder (burette). With a tap the titrant addition was regulated manually. A change in colour indicated the end of the titration reaction (endpoint). At first, only those titrations showing a significant colour change upon reaching the endpoint were performed. Later titrations were coloured artificially with an indicator dye. The precision achieved depended mainly on the chemist's skills and, in particular, on his ability for perception of different colours.

The modern way

Titration has experienced a strong development: manual and – later – motor-driven piston burettes allow accurate and repeatable titrant addition. Potentiometric sensors replace the colour indicators, thus achieving higher precision and accuracy of results. The graphical plot of potential versus titrant volume and mathematical evaluation of the resulting titration curve provides a more exact statement about the reaction than the colour change at the endpoint. With microprocessors the titration can be controlled and evaluated automatically. This represents an important step towards complete automation.

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3. Titration theory

3.1. Types of chemical reactions

There are several different kinds of chemical reactions that show changes which can be detected and thus utilised for analyses by titration. These categories are given below with and example reaction and some typical applications as well:

Acid/Base reactions:

HCl + NaOH → NaCl + H2O

Examples: Acid content in wine, milk, ketchup Content of HCl, HNO3, H2SO4.

 

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3.2. Titrant addition
3.3. Indication principles
3.4. Endpoint titrations - Equivalence point titrations
3.5. Fields of use
3.6. Advantages of titration

4. Automated titrators

4.1. Definition

A titrator is an instrument which allows the automation of all operations involved in titration: titrant addition, monitoring of the reaction (signal acquisition), recognition of the endpoint, data storage, calculation and results storage.

4.2. Working principle of automated titrators

Automated titrators follow a defined sequence of operations. This sequence is basically the same for all different models and brands. This sequence is performed and repeated several times until the endpoint or the equivalence point of the titration reaction is reached (titration cycle).

 

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4.3. Titrant addition
4.4. Measured value acquisition
4.5. Evaluation principles

 

5. How to get the best titration results

The primary goal of any analysis is to get accurate and precise results in as short a time as possible. Often neglecting the smallest thing can have an enormous impact on the reliability and quality of the final result. This chapter discusses some of the critical factors affecting titration results and provides some insight into how to eliminate some of the more common errors.

Quality management in titration

Quality management has become a relevant topic for the user of analytical instruments. It is mainly based on documentation of the proven technical specifications, the measurements and the analytical methods used. The documentation represents the basics of each quality management system and is requested by the auditors during periodical checks.

Quality management: why?

  • The customer requires correct results with respect to e.g. accuracy, precision, and reproducibility.
  • Pharmaceutical companies and government organizations (e.g., FDA, EPA) require traceability of the results and thus qualification of the instruments.

Both can be achieved by a complete documentation of results, compliance to technical specifications and method checks. The documentation procedure of analytical work in the laboratory is regulated by the applied QM-System (e.g. GLP), the proof of technical specifications is resumed in the certification procedure and specific analytical methods have to be tested in order to get correct results, i.e. the methods have to be validated. Last but not least, the instrument has to be maintained over the whole lifetime to guarantee continuation of correct results. These individual areas encompass the following:

GLP (Good Laboratory Practice):

Quality of planning, performing, controlling and reporting of laboratory work

Certification:

Quality of the instrument and of the measured values obtained by this instrument

Validation:

Quality of the analytical method and thus of the achieved results

Qualification:

Quality checking over the whole lifetime of the instrument

 

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5.1. Accuracy, precision and trueness
5.2. Types of errors
5.3. The best method for the job
5.4. Reagent handling
5.5. Sensor handling and maintenance
5.6. The effects of temperature on the results
5.7. Instrument care and maintenance
5.8. Sample handling
5.9. Summary

6. Chemical background

In the following chapters a brief introduction to chemical parameters which are relevant for the titration analysis is given. More information about chemical reactions can be found in ‘Fundamentals of Titration’ (ME-704153A).

6.1. The mole

In chemical calculations, specific units are used to describe a reaction. This is necessary since the number of atoms, molecules or ions in 1 g of sample can be ~ 1020. This means that 1 atom weighs approximately 10-20 g, a quantity with 20 decimal digits, i.e. a number on the twentieth digit after the comma! Thus, chemical calculations need more convenient units to calculate the amount of reagent and product involved in a reaction.

The base units of chemical calculations are associated with the base quantity ‘amount of substance’ and its base unit ‘mole’ of the International System of Units (SI). These concepts are defined by IUPAC (International Union of Pure and Applied Chemistry) as governing body.

 

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6.2. Reaction stoichiometry
6.3. Concentration of a titrant
6.4. Chemistry in titration
6.5. The ionic product of water
6.6. The strength of acids and bases
6.7. Acids and bases in non-aqueous solvents

7. Glossary

Titration, Titrant, Primary standard, Indication, End of titration, Equivalence point, Analyte , Standardisation, Stoichiometry

 

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