SEM-EDXRF Study of Two Chemical Modifiers Based on Platinum and Tungsten and Their Effect on ET-AAS Atomization of Lead

Abstract

The behavior of two chemical modi®ers based on platinum and tungsten, is studied in the two parts of this work. At ®rst, the chemical and morphological alterations of these during pyrolysis and atomization stages in electrothermal atomic absorption spectrometry are studied. The compounds were H 2 PtCl 6 and Na 2 WO 4 . A cylindrical graphite tube was used, and ®xed shaped rectangular graphite plates were put inside as platforms to prepare the specimens. The crystalline formations on the platforms were studied by scanning electron microscopy and the energy dispersive X-ray spectra allowed the estimation of the chemical composition changes of the modi®ers and the graphite surface. According to the spectra and the images obtained, both modi®ers where found to change their crystalline form at temperatures between 500±1250 C. Severe corrosion of the graphite surface was observed in case of H 2 PtCl 6 at temperature higher than 750 C, while minor damages were observed in case of Na 2 WO 4 . In the second part of this work, the ef®ciency of these modi®ers was tested for maximum loss-free pyrolysis temperature and atomization of lead by electrothermal atomic absorption spectrometry. The optimum results, concerning these parameters, obtained for medium concentration of the modi®ers. The effect of each modi®er on the atomization signal is discussed, and the optimum concentration of each one is estimated.

Advances in atomic emission, absorption and fluorescence spectrometry and related techniques

“…Studies on the modifying effect of Pt and W on the atomization of Pb were reported in a two part article by Zachariadis et al 237 The crystalline formations left on graphite platforms after the pyrolysis and atomization of Pt and W compounds were studied using SEM and the chemical composition of the residues and the substrate investigated using EDXRF. The crystalline form of each modifier was found to change at temperatures between 500 and 1250 uC.…”

Slurry sampling for the determination of thallium in soils and sediments by graphite furnace atomic absorption spectrometry

“…Zacharadias [22] using scanning electron microscopy and energy dispersive X-ray spectra (SEM-ED XRF) studied the morphology of specimens arising after the temperature modification of the graphite tube by Na 2 WO 4 and H 2 PtCl 6 . This paper encouraged the author to undertake more detailed study to find the optimal conditions for graphite tube modification by (NH 4 ) 2 WO 4 .…”