Determination of lead in biological materials by atomic absorption spectrometry sensitised with hydride generation

Abstract

A hydride generation system has been investigated in which the three flow-rates (purge, mixing and NaBH₄ addition) can be controlled. The sensitivity of plumbane generation is greatly affected by these three flows. Lead hydride was generated using the oxidant mixture HNO₃-H₂O₂ and the influence of various parameters on the sensitivity of the method was studied. It was found that the presence of transition metals such as Ni, Co and Mn considerably enhances the efficiency of lead hydride generation, with Ni being the most effective catalyst. This improvement is probably due to the formation of an unstable covalent hydride that favours plumbane formation. Increases in the signal depend on the concentration of NaBH₄, increases of 173 and 373% being obtained when NaBH₄ at 4 and 10%, respectively, was used. This sensitised method allows the determination of lead at low concentrations, and it has been applied to its determination in food and biological samples.