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

Methods for the direct trace determination of As, Sb, and Se in natural waters involving hydride generation, trapping, and atomization of the hydride in a graphite furnace have been developed. Graphite tubes permanently treated with uranium, tantalum, lanthanum oxide, niobium, beryllium oxide, chromium oxide, tantalum carbide, chromium carbide, and vanadium carbide were investigated for the in situ pre-concentration of the hydrides studied. The results obtained were compared with those achieved by iridium, tungstate and zirconium-treated graphite tubes (GT). Trapping on Zr-treated graphite tubes offers the best analytical performances for the hydrides studied, with characteristic 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 for 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 tubes. The accuracy was studied using TM-24, 1643d, CASS-3, and SLRS-4 reference materials. The 25 samples could be analyzed per hour.