Chapter 4: Determination of Trace Elements Using Flame AAS Check Access

Atomic absorption spectrometry involves the absorption of characteristic radiation provided by a hollow cathode lamp (HCL) of width of the order of 10⁻³ nm (atomic line spectra 10⁻⁵ nm), broadening resulting from disordered thermal motion, collision and splitting of the electronic levels of the absorbing atoms. The narrow line width coupled with a chopped or alternating light (AC) system leads to a high degree of freedom from interference due to absorption by other elements at their characteristic wavelengths. In the chopped or AC system, the modulation of the light beam, resulting in amplification of the modulated frequency only, ignoring the unmodulated direct current emissions from flame, etc., for total dissolved solids, is <5% at wavelength >300 nm. The light losses due to absorption and scattering by molecules or radicals are corrected by using deuterium, Zeeman or Smith Hieftji background corrections. The sensitivity of the technique is enhanced by hyphenation with a hydride generation kit or electrothermal atomization. The use of oxygenated organic solvents (specific gravity >0.75 and high flash points) enhances the signal due to their lower viscosity, specific gravity and surface tension, causing easier aspiration with finer nebulization besides exothermic combustion of oxygenated organic solvent.