Supported Liquid Membrane Enrichment Combined With Atomic Absorption Spectrometry for the Determination of Lead in Urine

Abstract

Supported liquid membrane (SLM) methodology was used for sample clean-up and enrichment of lead in urine prior to determination by AAS. Lead ions at pH 3 were extracted across a membrane solution containing 40% m/m di-2-ethylhexylphosphoric acid dissolved in kerosene and back-extracted into an acceptor solution of 1 mol l^{– 1} nitric acid. The mechanism of mass transfer is a proton gradient across the membrane. The concentration range investigated was between 5 and 80 ng ml^{– 1} and the extraction time was varied between 0.5 and 4 h, leading to enrichment factors of up to 200. The extraction efficiency was about 95%. The detection limit, expressed as 3ς of five replicate determinations, using a 45 min enrichment of a urine sample low in lead, was 0.1 and 6.0 µg l^{– 1} for ETAAS, and FAAS respectively. The results obtained by the developed method agreed with those obtained by direct ICP-MS determinations for reference urine samples and samples from occupationally lead-exposed workers. The linear correlation coefficient was 0.97, the slope of the regression line was 1.06 and the intercept was –0.37 µg l^{– 1}. The 95% confidence intervals for the slope and the intercept were 0.95 to 1.18 and –3.9 to 3.1, respectively. The results at the 95% confidence level for reference urine material were of 91 ± 1.5 and 92 ± 2.0 µg l^{– 1} for ICP-MS and SLM–AAS, respectively, which agreed well with the recommended value of 90 µg l^{– 1} (range 83–97 µg l^{– 1}).