Wall-to-platform migration in electrothermal atomic absorption spectrometry.: Part 2. Low-temperature migration characteristics of thallium, lead, cadmium, and manganese during thermal pretreatment

Abstract

Analyte migration, with respect to graphite surface temperature, was investigated quantitatively by observing analyte transfer from the initial deposition site on the inner wall of a graphite furnace to a cooler L'vov platform. Under typical thermal pretreatment conditions, species of thallium, lead, cadmium, and manganese were observed to migrate from the wall at temperatures of 250, 400–500, 300–350, and 1000°C, respectively. Migration probably occurs through low-temperature vaporization of oxides, metals, or salts of the analyte. These results highlight errors that may occur during routine analysis. Analytes that have migrated during thermal pretreatment may be atomized at a lower temperature, or may be lost through diffusion out of the ends of the furnace. The routine use of modifiers, such as mixtures containing palladium salts, is especially important for stabilizing analytes during thermal pretreatment, and thus preventing low-temperature migration.