Recent advances in the theory of atomisation in graphite furnace atomic absorption spectrometry: the oxygen-carbon alternative. Plenary lecture

Abstract

Two approaches to the problem of incomplete analyte atomisation in graphite furnace atomic absorption spectrometry based on the formation of either monoxides or carbides in the gas phase are compared. The discussion of the first approach provides an explanation of an apparent discrepancy between the comparatively high (10^–8–10^–7 atm) free oxygen partial pressure in the sheath gas and the absence of its effect on atomisation under typical analytical conditions. Within the second approach we have revealed, experimentally studied and theoretically interpreted the major features of the appearance in graphite furnaces of gaseous carbon at enhanced levels compared with equilibrium concentrations. The theory of gaseous carbide formation developed on this basis has provided an explanation for many unusual effects caused by the furnace material, sample vaporisation techniques and sheath gas (Ar vs. N₂) on the shape and magnitude of analytical signals, and theoretically substantiated the advantages of the stabilised temperature platform furnace.