Atomic absorption, equilibrium and mass spectrometry of germanium in graphite atomizers

Abstract

The atomization of Ge in graphite atomizers has been studied by electrothermal atomic absorption spectrometry (ETAAS) and electrothermal mass spectrometry (ETMS) and by calculation of thermochemical equilibrium. The evolution of GeO(g) from alkaline or nitric acid matrices and of GeS(g) from a sulfuric acid solution of germanium, at a relatively low temperature during pre-atomization or atomization, have been confirmed by ETMS. No gaseous germanium carbide was detected in ETMS experiments. Equilibrium calculations at low carbon activity show how GeO(g) may be evolved at 800 K by partial reduction of GeO₂. Further estimates of equilibrium for sodium germanate and sulfuric acid–GeO₂ matrices in both tube and platfrom atomizers show that many of the anomalies observed in the study of Ge by ETAAS may be explained by the assumption of a temperature or matrix-dependent carbon activity of the graphite, with consequent varying degrees of formation of GeO(g) or GeS(g).