Application of a ternary complex of chromium(VI) with phenylfluorone for cloud point extraction-spectrophotometric speciation of Cr(VI) and Cr(III) in aqueous solutions

A cloud point extraction-preconcentration by the formation of ternary complex was applied to the determination of trace Cr(VI) in water samples. The method is based on the formation of a purplish red complex of Cr(VI) with phenylfluorone in the presence of cetyltrimethylammonium bromide in acetate buffer media and mixed micelle-mediated extraction of the complex. The use of cloud point extraction (CPE) coupled with spectrophotometric detection allows the determination of chromium at mu g levels. The chemical variables affecting the analytical performance of the combined methodology were studied and optimised. The proposed method allowed the determination of chromium(VI) in the range 5-100 mu g/L with good precision and accuracy and the detection limit was found to be 1.04 mu g/L. The interference of concomitant ions on the CPE of Cr(VI) was investigated. Recoveries in the range of 97-102% were obtained by analysis of spiked real samples. The method was successfully applied to the determination of chromium in various water samples.