Comparison between AAS and AES:

As has already been emphasised, AAS and AES have become the mainstay of the analytical techniques for major and minor and trace element analysis within biological, geological, environmental and industrial samples. Both the techniques can be used for the determination of more than sixty elements, many of which can be determined at 1 ppm level. As regards their applicability, these two methods are complementary to each other by several points are common amongst them.

It must be kept in mind that only metals and metalloids can be determined by usual flame methods like FAAS. This is since resonance lines for nonmetals fall in vacuum UV region by some indirect methods have been developed for the same.

For example, chloride can be determined by precipitation with Ag⁺ and then either the excess of Ag⁺ or the one which has already reacted is measured. Same sulfur (383.7 nm) and phosphorus (525.9 nm) species exhibit sharp molecular band emission in the Ar-H2 flame. Generally, AAS is considered as more sensitive technique at wavelengths < 300 nm, whereas in visible region, AES is more advantageous. Some elements exhibit maximum sensitivity using molecular band emissions.

As the source of radiation in AAS is a hollow cathode lamp which emits the characteristic radiation of a given element, it is a unielemental technique. It is not convenient to measure more than one element at a time by AAS as it is difficult to incorporate more than a single source into the system. Each hollow cathode lamp emits efficiently the spectrum of only one, two, or three elements at a time, measuring additional elements requires substituting a new hollow cathode lamp. Though some advances have been made in continuum source atomic absorption spectrophotometry yet these arrangements are somewhat limited as sources extending within the ultraviolet region of the spectrum are not hugely available.