Behaviour of Selenium(iv) in a Transversely Heated Graphite Atomizer for Electrothermal Atomic Absorption Spectrometry in the Presence of Platinum Metals as Chemical Modifiers

Abstract

The effect of Pd, Pt, Rh, Ru and Ir on the behaviour of selenium in a transversely heated graphite atomizer for ETAAS was investigated. The chemical modifiers were used mainly in a thermally pre-reduced form. For all modifiers studied, the maximum pyrolysis and optimum atomization temperatures for selenium were approximately the same (about 1200 and 1600–1800 °C, respectively). There does not appear to be any correlation between these parameters and the melting-points of the modifiers used. Under optimized conditions, losses of about 10% of selenium at pyrolysis temperatures of 400–800 °C were observed for the pre-reduced Rh and Ru modifiers. The characteristic mass for selenium in the presence of pre-reduced Pt metal modifiers varied from 27.5 pg with the Pd modifier in a new graphite tube to 38.6 pg with the Pt modifier in a ‘used’ tube. All pre-reduced platinum group metals studied enabled the negative influence of up to 500 µg of chloride ion (as NaCl) on the determination of selenium to be eliminated. The efficiency of modification of chlorides of the platinum metals studied is very low, except for RhCl ₃ . In general, they can even act as an additional source of interference.