Comparison of atomization mechanisms for group IIA elements in electrothermal atomic absorption spectrometry

Abstract

Atomic absorption and mass spectrometry were used simultaneously to elucidate mechanisms responsible for atomization of Group IIA elements (beryllium, magnesium, calcium, strontium and barium) in pyrolytic graphite furnaces. Gaseous species of these elements, deposited as the nitrates and vaporized in 1 atm of nitrogen and in vacuum, were analysed in real-time by mass spectrometric sampling. The principal gas phase analyte species observed were carbides, oxides and hydroxides. Excluding beryllium, the data suggest that Group IIA atomization and carbide formation begin with the dissociative adsorption of the oxides and a perturbation of the surface state associated with the resulting adsorbed elements. Gas phase oxides are formed as a result of associative adsorption and the hydroxides are formed by homogeneous gas phase reactions of the carbides and oxides with water vapour.