Salient Features of AAS:

• AAS concerns the absorption of characteristic analyte radiation by the atomised analyte element in the ground state. A wavelength(s) of the radiation absorbed and an extent of the absorption form the basis of the qualitative and quantitative determinations respectively.
• Within flame atomic absorption spectrophotometry, either an air-acet ylene or a nitrous oxide-acetylene flame is used to evaporate the solvent and dissociate the sample into its component atoms.
• It not an absolute method of analysis; the routine quantitative determinations using AAS are based on calibration method. In addition, the internal standard method and standard addition methods are also employed.
• Compounds of the alkali metals, a few of the heavy metals such as lead or cadmium and transition metals like manganese or nickel are all atomised with good efficiency by flame However, a number of refractory elements like V, Zr, Mo and B do not perform well with a flame source.
• Graphite furnace atomic absorption spectrophotometry (GFAAS) in which the atomisation is achieved electrothermally, is a much more sensitive method as compared to flame AAS. A higher atom density and longer residence time within the graphite tube improve furnace AAS detection limits by a factor of up to 1000 compared to flame AAS. The detection limits might extend to the sub-ppb range.