Electrothermal Atomization with Atomic Absorption at Reduced Pressures for Studies of Analyte Distribution in Solids

Abstract

The spatial distribution of Pb in a NIST Standard Reference Material (SRM) C1253a copper alloy is determined by using an electrothermal atomizer atomic absorption spectrometry (ETA-AAS) system operated at reduced pressure. Three Pb absorbance peaks have been consistently observed at 0.1 Torr. It is proposed that the first peak belongs to the release process of Pb from the surface, the second peak may originate from grains until the Cu-Pb binary phase transformation to a homogeneous solution occurs, and the third peak arises from Pb in the bulk of the sample. The areas of the first two peaks may be used to determine the “near surface” and grain concentrations of analyte. However, the expulsion of analyte because of the coincident bulk vaporization of copper matrix produces a severely depressed analytical signal for the third peak. The data presented for the pressure-regulated ETA-AAS system suggest the feasibility of isolating and quantitatively measuring metals within the bulk and on or near the surface of solid samples when the metal of interest is of lower volatility than the host matrix.