A thermodynamic equilibrium model for atomization in graphite furnace atomic absorption spectrometry

Abstract

A thermodynamic (gas-phase) equilibrium model of atomization has been developed to account for the change in appearance temperatures of some elements when they are atomized in the presence of different amounts of O2 in argon purge gas. Experimental evidence of the effect of O2 on the atomic absorption pulse for ten elements is presented. Of these ten elements, five elements: Ag, Mn, Ni, Mg and Cu, show no measurable change in the appearance temperature or in the peak shape of their atomic absorption pulses when the O2 content of the purge gas is progressively increased from 0.005% to 1.0% (v/v); this phenomenon has been accounted for in terms of a lack of thermodynamic equilibrium in the gas phase. Shift of the atomic absorption pulses on the time axis (abscissa) for the other five elements: Pb, Sn, Si, Al and Ba, has been observed when the O2 content of argon purge gas is increased. The magnitude of change in the appearance temperature has been calculated for Pb, Sn and Si based on the thermodynamic (gas-phase) equilibrium model. The calculated results agree well with the experimentally observed changes in the appearance temperatures of these three elements.