Sample atomisation and oxidant release in graphite furnace atomic absorption spectrometry

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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.

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