Atomic absorption spectrophotometry:
Atomic absorption spectrophotometry (AAS) concerns the absorption of radiation by the atomised analyte element in the ground state. The atomisation is achieved through the thermal energy of the flame or electrothermally within an electrical furnace. The wavelength(s) of the radiation absorbed and the extent of the absorption form the basis of the qualitative and quantitative determinations respectively. As atomic absorption spectrophotometry is not an absolute method of analysis, the routine analytical methodology for quantitative determinations using AAS is based on calibration method. Besides that the internal standard method and standard addition methods are also employed.
A typical atomic absorption spectrophotometer consists of a source delivering the characteristic resonant radiation of the analyte, an atom reservoir into which the analyte is introduced and atomised, a monochromator, a detector and a readout device. In a typical flame atomic absorption spectrophotometric determination, the radiation from a hollow cathode lamp (or electrodeless discharge lamp) is made to fall on the sample of the analyte aspirated within the flame (or in the cuvette of an L'vov graphite furnace), while a part of it is absorbed. A transmitted radiation is then dispersed through a monochromator and sent to the detector. The detector output is suitably processed and is displayed by appropriate readout device. Like, UV-VIS spectrophotometers the atomic absorption spectrophotometers are also of two types' viz., single beam atomic absorption spectrophotometers and double beam atomic absorption spectrophotometers.