Flame atomic absorption spectrometry compared with other techniques

Flame emission spectrometry is used extensively for the determination of trace metals in solution and in particular the alkali and alkaline earth metals. The most notable applications are the determinations of Na, K, Ca and Mg in body fluids and other biological samples for clinical diagnosis. Simple filter instruments generally provide adequate resolution for this type of analysis. The same elements, together with B, Fe, Cu and Mn, are important constituents of soils and fertilizers and the technique is therefore also useful for the analysis of agricultural materials. Although many other trace metals can be determined in a variety of matrices, there has been a preference for the use of atomic absorption spectrometry because variations in flame temperature are much less critical and spectral interference is negligible. Detection limits for flame emission techniques are comparable to those for atomic absorption, i.e. from < 0.01 to 10 ppm (Table 8.6). Flame emission spectrometry complements atomic absorption spectrometry because it operates most effectively for elements which are easily ionized, whilst atomic absorption methods demand a minimum of ionization (Table 8.7). 

The approved reference method for enforcement purposes (CFR, 1982, 40 58) uses hi-vol samplers and measures lead by atomic absorption spectrometry (AAS). This laboratory method, which has been available in various analytical configurations for several decades, has been shown to be particularly reliable and sensitive for measuring lead quantitatively in a large range of environmental media. Flameless AAS is a more sensitive variation of this technique than conventional flame methods and has been the choice for many years. As with any lead measurement method, sample handling must minimize both contamination with lead and loss of lead from the sample. Comparatively, the contamination problem is still the more problematic and this is certainly the case for analyses in U.S. urban areas and in other industrialized nations (NAS/NRC, 1993 Patterson, 1983 Settle and Patterson, 1980). For air sample analyses, the codified reference method using AAS is quite adequate for a wide range of air lead concentrations. 

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