Chemical Reactions in an Electrothermal Graphite Furnace in the Presence of Lead, Magnesium Chloride and Chromium Nitrate

The effect of the addition of Cr(NO3)3 on graphite-furnace atomic absorption spectrometry for lead in the presence of MgCl2 was investigated from the viewpoint of its mechanism. X-Ray photoelectron spectrometry for the charring product of a mixture of MgCl2, Cr(NO3)3 and lead indicated the presence of Pb(II), Cr(III) and Cr(VI). An analysis of the charring product of a mixture of MgCl2 and Cr(NO3)3 by ion chromatography indicated a remarkable loss of chloride ions at a lower charring temperature (620K), before the fusion of lead chloride occurred. It was suggested that the loss of chloride ions resulted from the for mation of gaseous species, produced by redox reaction. Atomic absorption measurements of lead and its kinetic analysis were carried out in Mg(NO3)2, MgCl2, MgCl2 with Cr(NO3)3, Cr(NO3)3, CrCl3, (NH4)2CrO4 and K2Cr2O7. A comparison of the appearance temperatures of the lead signal and the Arrhenius activation energies of lead atomization among each matrix showed that Cr(III), e.g. Cr2O3, dominantly affected the atomization of lead.