Atomic absorption spectrometry in applied geochemistry

Most of this analytical requirement is met by atomic absorption spectrometry (AAS) methods about 70 percent of all geochemical samples are 

Flameless AAS methods have so far made little impact in applied geochemistry, except for methods for the element mercury, for which cold-vapour AAS is uniquely effective [2]. A plethora of methods are now in use ranging from simple attachments to standard instruments, to fully portable specific mercury meters of high sensitivity incorporating ingenious methods of background correction [3]. 

Graphite furnace atomisers are only used in special cases, i.e. when the analyte concentration is very low, (a) because the sampling rate is typically about 5—10 times slower than flame methods, (b) because interference effects tend to be severe and (c) because more skill is required for manual 

At the present time the technique of forming the volatile hydrides of certain elements (Ge, Sn, As, Sb, Bi, Se and Te), as a method of separation and rapid introduction of these elements into an atomiser (flame or hot tube), has had little impact in applied geochemistry. A few applications have been reported but are not yet widely used despite the very low detection limits which are obtainable. The main problems with the method are an abundance of interference effects, mainly from transition elements, and short linear calibration ranges. However Bedard and Kerbyson [4, 5] have shown that it is possible to separate in advance traces of As, Sb, Bi, Se and Te from pure copper, (the most serious interferer) by co-precipitating the elements on lanthanum hydroxide. It has further been shown that this precipitation method is applicable to the majority of interfering elements, and can be adapted to provide a rapid large batch method suitable for geochemical analysis of soil and sediment [6]. 

There is great interest in the volatile hydride forming elements as mineral pathfinders , as pollutants and, for selenium at least, as an essential dietary element. There are no existing alternative methods for the elements which are both accurate and cost-effective and there is little doubt that hydride methods will be used extensively in the near future. 

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