Simultaneous cloud point extraction of low levels of Cd, Cr and Hg in seaweed species prior to neutron activation analysis

Abstract

A one-step preconcentration cloud point extraction (CPE) method has been developed for the simultaneous determination of Cd, Cr, and Hg using a mixture of 1-(2-pyridylazo)-2-naphthol (PAN) and 1-(2-thiazolylazo)-2-naphthol (TAN) chelating agents and polyoxyethylene nonylphenylether-20 (PONPE-20) surfactant. The pH, concentration of PAN and TAN, concentration of PONPE-20, ionic strength and temperature affecting the sepa-ration were optimized. The recoveries of each of the elements under the optimum conditions of pH 8.6, [PAN/ TAN] = 1 x 10-4 M, [PONPE-20] = 0.1 % (m/v), ionic strength = 0.05 M KNO3, and temperature of 41 oC were > 98 %. The concentrations of the elements were determined by neutron activation analysis using the Dalhousie University SLOWPOKE-2 reactor (DUSR) facility. The detection limits of Cd, Cr, and Hg were 6.0, 3.6 and 1.2 ng g-1 respectively, and precision and accuracy of measurements were evaluated. The method was success-fully applied to the simultaneous determination of Cd, Cr, and Hg in fifteen Ghanaian seaweed species.

Journal of Applied Science and Technology Vol. 13 (1 & 2) 2008: pp. 48-54