Studies in hydride generation atomic fluorescence determination of selenium and tellurium. Part 1 - self interference effect in hydrogen telluride generation and the effect of KI

The effects of tetrahydroborate (0.02-1%) and iodide (0-3 M) were investiga ted in determination of tellurium and selenium by hydride generation atomic fluorescence spectrometry. The effect of tetrahydroborate and iodide conce ntration were tested on the shape of calibration curves in concentration ra nge of 1-1000 ng ml(-1) analyte. Reductant deficiency resulted in a moderat e sensitivity depression for tellurium but dramatically reduced the useful dynamic range down to 50 ng ml(-1). On the contrary, sclenium calibration c urves retained a linear character even under conditions generating strong s ensitivity depression. Curvature and rollover of tellurium calibration curv es has been addressed to a self-interference effect caused by the formation of finely dispersed elemental tellurium. Iodide ions were found to have be neficial or no negative effects in the hydrogen telluride generation. Addit ion of iodide on-line to the sample has been proved effective in the contro l of the self-interference effect and allows to work in mild reaction condi tions. Moreover, it allows a good control of Cu(II) interference and elimin ates Ni(II) and Co(II) interferences. The method has been successfully appl ied to determination of tellurium in copper and lead ores certified referen ce materials. (C) 2000 Elsevier Science B.V. All rights reserved.