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 μg 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 μg/L with good precision and accuracy and the detection limit was found to be 1.04 μg/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.