Applications of Atomic Absorption Spectrometry
Atomic absorption spectrometry is one of the most widely used techniques for the determination of
metals at trace levels in solution. Its popularity as compared with that of flame emission is due to its
relative freedom from interferences by inter-element effects and its relative insensitivity to variations in
flame temperature. Only for the routine determination of alkali and alkaline earth metals, is flame
photometry usually preferred. Over sixty elements can be determined in almost any matrix by atomic
absorption. Examples include heavy metals in body fluids, polluted waters, foodstuffs, soft drinks and
beer, the analysis of metallurgical and geochemical samples and the determination of many metals in
soils, crude oils, petroleum products and plastics. Detection limits generally lie in the range 100–0.1
ppb (Table 8.4) but these can be improved by chemical pre-concentration procedures involving solvent
extraction or ion exchange.
Currently a balance seems to have been reached in the use of the various techniques for the
determination of metals at trace levels. In its modern form AAS remains important and competitive
where small ranges of elements need to be determined in samples. Sensitivities obtainable by flame
AAS are often similar to those for ICP-AES and where graphite furnace volatilization is used they are
not infrequently superior (Table 8.4).
8.7—
Atomic Fluorescence Spectrometry
Summary
Principles
Characteristic fluorescent radiation emitted from an atomic vapour of the analyte following irradiation
with UV/visible primary radiation of broad spectrum.
Instrumentation
Excitation of sample atoms by primary radiation from a high-intensity broad spectrum or element
selective source. Samples atomized in a chemical flame using a circular burner. Optics to isolate
emission line and photomultiplier to measure its intensity.
Applications
In principle applicable to a wide range of elements but in practice limited to the volatile metal Hg, and
elements that can be made volatile as hydrides or organo-derivatives (As, Se, Te, Bi, Cd). Sensitivity
100 – 0.1 ppb. Relative precision, 0.5–2%.
Disadvantages
Signal can be very sensitive to flame characteristics. Limited range of applications.