Supported liquid membrane enrichment combined with atomic absorption spectrometry for the determination of lead in urine

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 3 sigma of five replicate determinations, using a 45 min enrichment of a urine sample low in lead, was 0.1 and 6.0 mu g 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 mu g 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 mere of 91 +/- 1.5 and 92 +/- 2.0 mu g l(-1) for ICP-MS and SLM-AAS, respectively, which agreed well with the recommended value of 90 mu g l(-1) (range 83-97 mu g l(-1)).