Page 245 - Tandem Techniques

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Chapter 6
Gas Chromatography/Atomic Spectroscopy (GC/AS) Tandem Systems

The combination of a gas chromatograph with an atomic spectrometer is not an arrangement that is as
popular as many other tandem instruments. However, this particular form, does have certain areas of
application where it can be extremely useful. There are three types of analyses in which the GC/AS
system is most often employed. The first, and probably the most important, is to provide elemental
analysis of the eluted components, and consequently their empirical formulae, to aid in identifying
unknown substances. The second is its use as a specific detector to reduce the need for high-resolution
columns when analyzing highly complex mixtures. Third the GC/AS tandem system is often used for
trace analysis and, in particular, for following the speciation of selected elements in a mixture. Both the
absorption and emission spectrometers have been used in conjunction with the gas chromatograph.
However, whereas the absorption spectrometer has been frequently used in LC/AS tandem systems, the
combination of the gas chromatograph with the atomic emission spectrometer is probably the more
common.

Atomic emission spectrometers can basically take two forms the spark discharge spectrometer and the
plasma spectrometer. The plasma emission spectrometers are the most popular types of atomic emission
spectrometer and the plasma can be generated in three ways. Plasma can be formed by direct current
discharge, inductively coupling and by microwave