Studies on the mechanism of atom formation in graphite furnace atomic absorption spectrometry

The mechanism of atom formation for a number of elements in a Perkin-Elmer heated graphite atomizer, HGA 2100, has been studied using a combined thermodynamic and kinetic approach. Assuming that an analyte surface-gas phase equilibrium exists within the furnace and the production of observable atoms is characterized by a unimolecular rate constant, a plot of the logarithm of the absorbance as a function of the inverse of the absolute temperature yields a straight line from which the activation energy, E/sub a/, of the limiting step in the atomization pathway can be obtained. These E/sub a/ values reveal that three major atomization mechanisms are operative: thermal dissociation of the analyte oxide or halide, and carbon reduction of the oxide followed by atomization of the free metal