MASS-SPECTROMETRY AND EQUILIBRIUM OF OXIDES OF ARSENIC, GALLIUM AND INDIUM IN THE GRAPHITE-FURNACE

Calculations of the equilibrium in the reduction of As2O3, Ga2O3 and In2O3 by graphite show that the gas-phase oxides As4O6(g), Ga2O(g) and In2O(g) may be formed during the analysis for arsenic, gallium and indium by graphite furnace atomic absorption spectrometry (GFAAS). These gas-phase oxides were detected by mass spectrometry during graphite furnace atomisation in vacuo. The As4O6(g) is likely to be lost from the furnace during prolonged drying of arsenic samples at relatively low temperatures; Ga2O(g) and In2O(g) may be formed during atomisation cycles above 1000 K. These effects may cause substantial losses in sensitivity for these elements during GFAAS.