AAS is a time-proven analysis used extensively in Pharmacopoeial and environmental analysis for the quantitative determination of metals, mostly as minor or trace constituents. It is now becoming superseded by the more modern ICP techniques, although it is still widely used in pharmacopoeial methods for single-element analysis.
The sample is injected into a flame, and the instrument measures light absorption at characteristic wavelengths as it passes through the atomic vapour generated in the flame. The light comes from a hollow cathode lamp specific to the element being determined.
The technique has the following modes of operation:
- Flame absorption. The sample is introduced as a mist into a flame for atomic absorption measurements
- Flame emission. Most used for the alkali elements that emit light, such that their light emission can be used to determine the concentration of that element in solution.
- Cold vapour: Used specifically for mercury only, as it is the only element that will generate an atomic vapour at room temperature. Stannous chloride added to the sample solution generates mercury vapour, which is blown into a quartz tube placed in the light path in place of the burner.
