Determination of Cr(III) and total chromium in water samples by cloud point extraction and flame atomic absorption spectrometry

Abstract

A sensitive and selective method has been developed for the speciation of chromium in water samples based on cloud point extraction (CPE) separation and preconcentration and determination by flame atomic absorption spectrometry. In the CPE method, Cr(III) reacts with acetylacetone yielding a hydrophobic complex, which is entrapped in the Triton X-100 surfactant-rich phase, whereas Cr(VI) remained in aqueous phase. Thus, separation of Cr(III) and Cr(VI) could be realized. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by using ascorbic acid as reducing reagent. Under the optimal conditions, the detection limit of this method for Cr(III) was 0.32 ng mL−1 with an enrichment factor of 35, and the relative standard deviation was 3.4% (c = 100 ng mL−1, n = 7). The method has been applied to the speciation of chromium in natural water samples with satisfactory results.