Atomisation in graphite furnace atomic absorption spectrometry: atmospheric pressure vis-à-vis vacuum vaporisation

Abstract

Arrhenius plots were prepared from signals obtained for the atomisation of Pb, Bi and Au from a graphite surface at atmospheric pressure and in vacuum at 10^–9 atm. Spatially integrated absorbance was recorded for atmospheric pressure studies and mass spectral intensity for vacuum runs. Comparison of activation energies (E_a) calculated from the leading edges of the signals showed no significant differences between atmospheric and vacuum vaporisation. The E_a values are thus not influenced by potential radial inhomogeneities in the vapour densities within the tube. For the elements and conditions used in this study, Arrhenius data support a vaporisation model that assumes the analyte to be present on the graphite surface in the form of microparticles as opposed to a monolayer.