Cloud point extraction for ultra-trace Cd determination in microwave-digested biological samples by ETAAS

ARANDA,P,R.GIL,R,A.MOYANO,S.DE VITO,I.MARTINEZ,L,D.

TALANTA

Elsevier

Lugar: London; Año: 2008 vol. 77 p. 663 - 666

0039-9140

Cloud point extraction (CPE) has been used for the preconcentration of cadmium, after the formationof a complex with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP), and further determinationby graphite furnace atomic absorption spectrometry (ETAAS) using polyethyleneglicolmono-pnonyphenylether(PONPE 7.5) as surfactant. The chemical variables that affect the cloud point extractionwere optimized. The separation of the two phases was easily accomplished by cooling the mixture inorder to make more viscous the surfactant-rich phase. In order to establish the optimum conditions forthe determination of Cd by ETAAS, Pd + Mg, Pt, Ir, Rh and Ru were studied as chemical modifiers. Thebest 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 theoptimal conditions was 0.008gL−1. The precision for 10 replicate determinations at 0.2gL−1 Cd was3.5% relative standard deviation (R.S.D.). The calibration graph using the preconcentration method waslinear with a correlation coefficient of 0.9984 at levels close to the detection limit up to at least 1.0gL−1.The method was successfully applied to the determination of cadmium in urine samples and in a waterstandard reference material.