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-treat ed with about 1.2-1.3 mu mol of Zr or W, and was evaluated as a perman ent modifier in electrothermal atomic absorption spectrometry, The nob le metal is not vaporized from the integrated platform of the transver se-heated graphite atomizer, provided that the atomization and clean-o ut temperatures do not exceed 2050-2100 and 2100-2200 degrees C, respe ctively, Under comparable conditions, Pd exhibits much worse thermal b ehaviour, 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 integr ated absorbance measurements with the Ir-Zr-treated platforms are 92, 30, 176, 2.4, 35, 50, 65, 71 and 45 pg, respectively, Vaporization tem peratures are generally above 1000 degrees C, except for Cd, The effec t of atomization temperature on sensitivity in peak height and integra ted absorbance measurements is discussed, Double peaks were observed f or Bi and Te with Ir-W-treated platforms.