Combination of hydride generation and graphite furnace atomic absorption spectrometry for the determination of lead in biological samples

Abstract

The optimum conditions for the adsorption of lead hydride in a graphite tube prior to the determination of lead have been investigated. Lead hydride was generated in an H₂O₂-HNO₃ medium in the presence of Ni as catalyst. Hydride generation is selective for the determination of lead in biological samples but the method is not sensitive enough for its determination at very low concentrations. Hydride generation combined with graphite furnace atomic absorption spectrometry (GFAAS) gives a five-fold enhancement of sensitivity with respect to that using a conventional atomisation cell. Furthermore, the selectivity using the combined technique is higher than that obtained using GFAAS alone. If old tubes are used, better sensitivity is obtained than with new ones. Thus, an advantage of the proposed method is that it uses tubes that are already in service. The optimum conditions for argon flow-rates for lead hydride adsorption and the temperature programme for lead vaporisation are reported. The proposed method has been applied successfully to the determination of lead in food samples.