Cloud point preconcentration prior to capillary zone electrophoresis: Simultaneous determination of platinum and palladium at trace levels

S. CERUTTI, M.F. SILVA, J.A. GÁSQUEZ, R.A. OLSINA, L.D. MARTINEZ

ELECTROPHORESIS

Wiley-VCH Verlag

Año: 2005 vol. 26 p. 3500 - 3506

0173-0835

The incorporation of a cloud point extraction (CPE) step prior to capillary electrophoresis(CE) for simultaneously determining platinum and palladium at sub-ug/L levels ispresented and evaluated. The analytes were extracted as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complexes, at pH 2.0, mediated by micelles of the nonionic surfactantpolyethyleneglycolmono-p-nonylphenyl ether (PONPE 7.5). The separation–determination step was developed from 150 uL of the extracted surfactant-rich phasediluted with 50 uL of acetonitrile (ACN). An exhaustive study of the variables affectingthe cloud point extraction with PONPE 7.5 and the CZE step was done. The type andcomposition of the background electrolytes (BGEs) were investigated with respect toseparation selectivity, reproducibility, and stability. A BGE of 50mM monobasic sodiumphosphate containing 30% ACN, pH 4.53 was found to be optimal for the separation ofmetal chelates. Detection was performed at 576 nm. An enrichment factor of 250 wasobtained for the preconcentration of 50mL of sample solution. The detection limits forthe preconcentration of 50mL of sample were 0.04 ug/L for Pt and 0.08 ug/L for Pd. Asan analytical demonstration, ultratrace concentrations of platinum and palladium wereconveniently quantitated in spiked water and urine samples.