Thermally stabilized iridium on an integrated, carbide-coated platform as a permanent modifier for hydride-forming elements in electrothermal atomic absorption spectrometry. Part 1. Optimization studies

Abstract

Iridium (2 µg) was deposited on a carbide-coated platform, pre-treated with about 1.2–1.3 µmol of Zr or W, and was evaluated as a permanent modifier in electrothermal atomic absorption spectrometry. The noble metal is not vaporized from the integrated platform of the transverse-heated graphite atomizer, provided that the atomization and clean-out temperatures do not exceed 2050–2100 and 2100–2200 °C, respectively. Under comparable conditions, Pd exhibits much worse thermal behaviour, being volatilized above 1300 and 1500 °C from Zr- and W-treated platforms, respectively. Pyrolysis–atomization curves were plotted for numerous hydride-forming and volatile analytes: Sb, As, Bi, Cd, Pb, Te, Tl, Sn and Se. The best characteristic masses for integrated absorbance measurements with the Ir–Zr-treated platforms are 92, 30, 176, 2.4, 35, 50, 65, 71 and 45 pg, respectively. Vaporization temperatures are generally above 1000 °C, except for Cd. The effect of atomization temperature on sensitivity in peak height and integrated absorbance measurements is discussed. Double peaks were observed for Bi and Te with Ir–W-treated platforms.