THERMALLY STABILIZED IRIDIUM ON AN INTEGRATED, CARBIDE-COATED PLATFORM AS A PERMANENT MODIFIER FOR HYDRIDE-FORMING ELEMENTS IN ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY .1. OPTIMIZATION STUDIES

Iridium (2 mu g) was deposited on a carbide-coated platform, pre-treated with about 1.2-1.3 mu mol 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 degrees C, respectively, Under comparable conditions, Pd exhibits much worse thermal behaviour, being volatilized above 1300 and 1500 degrees 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 degrees 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.