Lead atomisation from soil by slurry introduction electrothermal atomisation atomic absorption spectrometry. Part 1. Effects of matrix components on the absorbance versus time profile

Abstract

A typical soil matrix was modelled, in order to examine the effects of matrix components on the absorbance signal for Pb using L'vov platform atomisation. Components studied were clay (montmorillonite), organic carbon (as humic acid), phosphate, Mg²⁺ and Cl^–. Lead is adsorbed on the clay particles, and this delayed the signal to a higher temperature compared with an aqueous Pb solution. Phosphate and Mg²⁺ also delayed atomisation, but not at the low concentrations normally found in soil. There was no Cl^– interference at normal concentrations in soil. Organic carbon caused Pb to atomise at a lower temperature. This could lead to a systematic error, compared with aqueous standards, if atomisation occurs prior to conditions being nearly isothermal in the graphite furnace. The use of a matrix modifier is recommended to overcome this interference.