Instant Notes: Analytical Chemistry

Section F – Combined techniques

F1 ADVANTAGES OF COMBINED

TECHNIQUES

Other sections of this text describe some of the many techniques and methods

of qualitative, quantitative and structural analysis. In the case of samples

originating in the real world, that is from man-made materials, environmental

sampling or complex natural mixtures, each of the techniques has a place, and

often several must be used in order to obtain a complete overview of the nature

of the sample.

Particular emphasis has been placed on separation and spectrometric tech-

niques in Sections D and E. Together with the electrochemical techniques of

section C, they represent the major tools of the analytical chemist. Other special

techniques, such as thermal analysis, may also be combined with them to reveal

precise details of the processes occurring (see Topic G4).

If an unknown material is presented for analysis, it should first be determined

whether the sample is a single substance, or a mixture. The purity of substances

such as pharmaceuticals is very important. Separation by an appropriate tech-

nique (Section D) should reveal the number of components in the sample.

Even single substances can be complex chemical molecules. If these are to be

assigned a unique identity, then several of the molecular spectrometric tech-

niques may need to be used on the sample.

Instrumentation may need to be specially adapted if two or more techniques

are to be interfaced successfully; for example, passing the effluent gas emerging

Combined
approach

Key Notes

The strategy for analyzing a sample to determine its composition,

structure and properties often requires the application of more than one

of the analytical techniques described in this text. The use of multiple

techniques and instruments, which allow more than one analysis to be

performed on the same sample at the same time, provide powerful

methods for analyzing complex samples.

In order to solve many analytical problems, it is necessary to use a

number of techniques and methods. The components of naturally

occurring substances may need to be separated and identified. Problem

solving is aided if several analytical techniques are used, and time may

be saved if the analyses are performed simultaneously.

By using many techniques either separately or in combinations, the

advantages to the analyst in the additional information, time saving and

sample throughput are considerable.

Related topics Separation techniques (Section D) Sensors, automation and

Spectrometric techniques (Section E) computing (Section H)

Combined approach

Problem solving

Advantages