Determination of lead by continuous-flow hydride generation and atomic absorption spectrometry: Comparison of malic acid—dichromate, nitric acid—hydrogen peroxide and nitric acid—peroxodisulfate reaction matrices in combination with sodium tetrahydroborate

Abstract

A continuous-flow hydride generator is combined with a heated quartz tube atomizeratomic absorption spectrometer system for the trace determination of lead. Malic acid K 2Cr 2O 7, HNO 3—H 2O 2 and HNO 3—(NH 4) 2S 2O 3 are all effective for plumbane generation by means of sodium tetrahydroborate. The relative merits of these systems are investigated in terms of sensitivity, efficiency of plumbane generation and interferences. The sensitivities (0.0044 absorbance) obtained under the recommended conditions for the three systems are 3.2, 1.7 and 1.1 ng Pb ml -1, respectively, whereas plumbane generation efficiencies are 33%, 47% and >80%, respectively, for 1 μg Pb ml -1. Silver, Au, Cu and Cd interfere seriously in all reaction systems. A dithizone extraction and back-extraction method is utilized to eliminate interfering ions, followed by reduction of the resulting solution in the peroxodisulphate system. The proposed method is applied to water samples and NBS 1566 oyster tissue.