Permanent iridium modifier deposited on tungsten and zirconium-treated platforms in electrothermal atomic absorption spectrometry: vaporization of bismuth, silver and tellurium

The stabilizing role of permanent iridium modifier deposited on tungsten-tr eated (WTP) and zirconium-treated (ZrTP) platforms of transversely heated g raphite atomizer (THGA) was studied in detail by electrothermal atomic abso rption spectrometry (ETAAS) and different surface techniques in model exper iments for Ag, Bi and Te. The comparison of the stabilizing efficiency of p ermanent Ir modifier on WTP and ZrTP and each of the single components, rev eals the better effect of Ir on WTP and Ir itself. The extent of analyte lo sses during pre-atomization and the strength of analyte association with th e modifier were estimated by the plotting of 'differential vaporization cur ves'. The existence of double peaks of Ag, Bi and Te in WTP and Ir on WTP w as confirmed and possible reasons for their formation were discussed. The a bsorbance profiles presented as differential curves reveal an existence of at least two different types of precursors determining processes of atom ge neration. The observed differences in the behavior of Ir permanent modifier on WTP and ZrTP, respectively, were explained by the different extent of i ridium-tungsten and iridium-zirconium interaction and surface distribution. XRF, ESCA and SEM studies reveal non-uniform distribution of the modifier on the graphite substrate and the presence of oxide containing species on t he surface. (C) 1999 Elsevier Science B.V. All rights reserved.