ONLINE PRECONCENTRATION OF SELENIUM(IV) AND SELENIUM(VI) IN AQUEOUS MATRICES FOLLOWED BY LIQUID CHROMATOGRAPHY INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY DETERMINATION

A study was carried out for the determination of selenite and selenate from water matrices using ion-pairing reversed-phase or anion exchange liquid chromatography followed by determination with inductively coupled plasma mass spectrometry (LC-ICP-MS), which used conventional pneumatic nebulization as sample introduction technique. The detection limits and background levels for the anion exchange chromatography were lower than those for the ion-pairing separation method. Based on the optimum conditions obtained with a 25 mu l sample injection loop, a preconcentration column was coupled on-line with the anion exchange LC-ICP-MS system. The capability of this simple on-line preconcentration procedure was demonstrated for the analysis of various water matrices spiked with selenite and selenate including high salt-containing water, river, tap, and well water samples. The detection limits (3 sigma) obtained by preconcentration of 2-10 ml of the high salt-containing water and other aqueous matrices were 0.16-0.42 and 0.08-0.19 mu g l(-1) of Se for selenite and selenate, respectively. These relative detection limits were ca. two orders of magnitude better than those obtained with a 25 mu l sample loop.