Sample atomisation and oxidant release in graphite furnace atomic absorption spectrometry

Abstract

Time-resolved measurements of the release of CO and oxidants during the thermal decomposition of samples in a graphite furnace have been made spectroscopically by monitoring the attenuation of CO(0,0) and CO(1,2) bands at 154.3 and 163.1 nm, respectively, emitted from a hollow-cathode discharge supplied with 10^–3 atm CO. Low-temperature carbon reduction of analyte oxides, concurrent carbon reduction-vaporisation and thermal decomposition-vaporisation reactions could be delineated through isolation of the CO and oxidant source functions. A major source of free oxygen in the furnace arises from analyte oxide decomposition. The capacity of glassy carbon tubes to accommodate low-temperature release of excess oxidants is inferior to that of electrographite or pyrolytic graphite coated tubes. Chemisorption of O₂ on to the tube surface influences the low temperature reduction capacity of the graphite tube and may play a role in the thermal shifting of absorption pulses and the “first shot back” phenomenon.