SPECIATION OF CR(III) AND CR(VI) BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY USING UV-DETECTION

A method for the simultaneous determination of Cr(III) and Cr(VI) in water samples is described. The different reaction products of Cr(III) and Cr(VI) species with ammonium pyrrolidinedithiocarbamate (APDC) are extracted with ethyl acetate and determined by reversed phase HPLC using UV-detection. The procedure is optimized and its detection limit accordingly improved as compared to literature data. The detection limits achieved are 2.4 mug/l for Cr(III) and 2.1 mug/l for Cr(VI) and the calibration curves are linear between 5 mug/l and 5000 mug/l. For the speciation of Cr, APDC was demonstrated to be more suitable as chelating agent than sodium diethyldithiocarbamate (NaDDC). The procedure was applied to the determination of both Cr species in galvanic waste waters and its accuracy was approved by comparing the results (at the 100 mug/l level) with those of a photometric determination of Cr(VI) species.