Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

摘要

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-l 14) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30 μgL~(-1) and 2.6 μgL~(-1), respectively. A precision expressed as relative standard deviation (RSD, n = 10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10μgL~(-1) and 30μgL~(-1) respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10μgL~(-1) and 30μgL~(-1), respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilheus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.