MECHANISMS CONTROLLING THE DIRECT SOLID SAMPLING OF SILICON FROM GOLDSAMPLES BY ATOMIC-ABSORPTION SPECTROMETRY WITH ELECTROTHERMAL ATOMIZATION .1. ANALYTE MIGRATION TO THE SOLID-SURFACE

The results of electrothermal atomic absorption spectrometry (ETAAS) i nvestigations of Si vaporization from solid gold samples indicate that Si is released only after melting of the gold matrix, and the migrati on of Si to the surface is assisted by the formation of convection cel ls in the melt. This convection is driven by the thermal gradients in the sample. Diffusion alone, in either the solid or the melt, is too s low to account for the relatively short time for total Si release befo re a significant portion of the gold matrix is depleted. Silicon that is carried by the induced convection to the surface is readily vaporiz ed. It is shown that the liquidus lines of the binary phase diagrams a ssociated with a gold solvent can be used to predict the existence of analyte carryover in the gold, Consequently, these diagrams offer a me ans of identifying, a priori, candidate elements that may be determine d by solid sampling ETAAS in gold, via aqueous solution calibration.