Atomisation characteristics of lead determined in alumina matrices by slurry-electrothermal atomisation atomic absorption spectrometry

Abstract

The electrothermal atomisation characteristics of lead adsorbed on and occluded in two types of Al₂O₃ slurry are examined. The work was undertaken to understand better the atomisation of lead from soil slurries, where the metal is mostly adsorbed on the active surface of clay particles. “High-temperature alumina”(HTA) is nearly anhydrous Al₂O₃, and “low-temperature alumina”(LTA) is a mixture of hydrated oxides. The HTA matrix does not seriously affect the atomisation of lead and its quantitative determination is possible using platform atomisation and aqueous standards if an Mg + PO₄ ^3– matrix modifier is added to samples and standards. However, lead is strongly retained by LTA and kinetic studies indicate that atomisation may occur via the breaking of covalent Pb–O bonds between lead and the particles. Consequently the atomisation appearance time is delayed, and if lead is occluded in LTA systematic errors will occur. However, if lead is adsorbed on LTA, it could still be determined with aqueous calibration standards if a matrix modifier is used. This is similar to the way in which lead is incorporated in soil.