CLOUD POINT EXTRACTION FOR ULTRA-TRACE Cd DETERMINATION IN MICROWAVE-DIGESTED BIOLOGICAL SAMPLES BY ETAAS

PEDRO R. ARANDA, RAÚL A. GIL, SUSANA MOYANO, IRMA DE VITO, LUIS D. MARTINEZ

TALANTA

Elsevier

Año: 2008 vol. 77 p. 663 - 666

0039-9140

Cloud point extraction (CPE) has been used for the preconcentration of cadmium, after the formation of a complex with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP), and further determination by graphite furnace atomic absorption spectrometry (ETAAS) using polyethyleneglicolmono-pnonyphenylether (PONPE 7.5) as surfactant. The chemical variables that affect the cloud point extraction were optimized. The separation of the two phases was easily accomplished by cooling the mixture in order to make more viscous the surfactant-rich phase. In order to establish the optimum conditions for the determination of Cd by ETAAS, Pd + Mg, Pt, Ir, Rh and Ru were studied as chemical modi.ers. The best thermal stabilization was obtained with Pd + Mg, with a maximum pyrolysis temperature of 1100 °C. Under the optimum conditions i.e., pH 9.0, [5-Br-PADAP] = 2.0×10-5 mol L-1, [PONPE 7.5] = 0.02% (w/v), an enhancement factor of 22-fold was reached. The lower limit of detection (LOD) obtained under the optimal conditions was 0.008_gL-1. The precision for 10 replicate determinations at 0.2 µgL-1 Cd was 3.5% relative standard deviation (R.S.D.). The calibration graph using the preconcentration method was linear with a correlation coef.cient of 0.9984 at levels close to the detection limit up to at least 1.0µgL-1. The method was successfully applied to the determination of cadmium in urine samples and in a water standard reference material.