BEHAVIOR OF SELENIUM(IV) IN A TRANSVERSELY HEATED GRAPHITE ATOMIZER FOR ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY IN THE PRESENCE OF PLATINUM METALS AS CHEMICAL MODIFIERS

The effect of Pd, Pt, Ph, 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, F or all modifiers studied, the maximum pyrolysis and optimum atomizatio n temperatures for selenium were approximately the same (about 1200 an d 1600-1800 degrees C, respectively), There does not appear to be any correlation between these parameters and the melting-points of the mod ifiers used, Under optimized conditions, losses of about 10% of seleni um at pyrolysis temperatures of 400-800 degrees C were observed for th e pre-reduced Ph and Ru modifiers, The characteristic mass for seleniu m in the presence of pre-reduced Pt metal modifiers varied from 27.5 p g with the Pd modifier in a new graphite tube to 38.6 pg with the Pt m odifier in a 'used' tube, All pre-reduced platinum group metals studie d enabled the negative influence of up to 500 mu g of chloride ion (as NaCl) on the determination of selenium to be eliminated, The efficien cy of modification of chlorides of the platinum metals studied is very low, except for RhCl3. In general, they can even act as an additional source of interference.