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ionization source of the spectrometer. It follows that the eluent from a liquid chromatography column is
ideally suited for direct injection into the atomic spectrometer by means of a simple nebulizer. The
liquid chromatograph has been coupled with different forms of atomic spectrometer in a variety of
ways, and some of these will now be discussed.

Liquid Chromatography Flame Atomic Absorption Spectroscopy (LC/AAS) Systems

The flame AAS is highly element-specific, far more so than the electrochemical detector, but it is not as
sensitive. An atomic emission spectrometer, or an atomic fluorescence spectrometer, will readily
provide simultaneous multi-element detection, but this is more difficult with the flame AAS. It follows
that most LC/ flame AAS combinations are usually set to monitor one element only, throughout the
total chromatographic separation.

As the main applications of LC/ Flame AAS is to help determine metal speciation in samples and not
merely to identify the presence of a particular element, it is not sufficient to detect the presence of lead,
mercury or chromium. One must also to be able to identify the form in which they are present.
Depending on the chemical form of a mercury compound, it may or may not be highly toxic. It is also
well-known that if chromium is present in the tertiary form it is not particularly dangerous; conversely,
in its sixth valency state it is strongly carcinogenic. In order to successfully utilize the LC/AAS
combination, both the chromatograph and the spectrometer must be optimized, which has been
discussed in some detail in a number of publications [1-3]. It has been claimed [1] that the poor
sensitivity that has been obtained from the LC/AAS system, relative to that from the atomic
spectrometer alone, was due to the dispersion that takes place in the column. Although substantially
true, this misunderstanding arises from the fact that the spectroscopist views the chromatograph as just
another sampling device and not as a separation system. The point of interfacing a liquid
chromatograph with an absorption spectrometer is to achieve a separation before detection.