Page 167 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon

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Figure 7.3
Typical cold vapour generation AAS system used for mercury
determination. The same system can be used with a flame in place
of the Pyrex tube to allow the determination of
hydride-forming elements.

problems. Spurious absorption signals can often be seen and the use of background correction is to be
preferred. Detection limits of about 1 ng are achievable. Certain elements, particularly silver, gold,
palladium and platinum, are reported to cause chemical interferences in the reduction stage. Specialist
fluorescence-based instrumentation has also been developed for the determination of mercury. Argon is
used as both a sheathing gas to enclose the plume of mercury and as the flushing gas to transport it to
the detector. This is because argon causes less quenching of the flame than nitrogen.

7.5.3 Other Vapour Techniques

There have been a few research papers reporting the use of other vapour generation techniques to
volatilize analytes that form unstable hydrides, or had previously been thought not to form vapours at
room temperature. Examples include the use of sodium tetraethylborate to form volatile ethyl
compounds of cadmium, lead and thallium.