Comparative study of different permanently-treated graphite tubes for the determination of As, Sb, and Se in natural waters by hydride generation-electrothermal atomic absorption spectrometry

Methods for the direct trace determination of As, Sb, and Se in natural wat ers involving hydride generation, trapping, and atomization of the hydride in a graphite furnace have been developed. Graphite tubes permanently treat ed with uranium, tantalum, lanthanum oxide, niobium, beryllium oxide, chrom ium oxide, tantalum carbide, chromium carbide, and vanadium carbide were in vestigated for the in situ pre-concentration of the hydrides studied. The r esults obtained were compared with those achieved by iridium, tungstate and zirconium-treated graphite tubes (GT). Trapping on Zr-treated graphite tub es offers the best analytical performances for the hydrides studied, with c haracteristic masses of 45, 17 and 90 pg for As, Sb, and Se, respectively. in addition, the use of U-treated GTs offers adequate trapping efficiency f or arsine; for stibine, the use of Cr3C2-, Cr2O3-, TaC-, VC- and U-treated GTs gives analytical performances similar to the use of Ir- and W-treated t ubes. The accuracy was studied using TM-24, 1643d, CASS-3, and SLRS-4 refer ence materials. The 25 samples could be analyzed per hour. (C) 2001 Elsevie r Science B.V. All rights reserved.