SIMULTANEOUS DETERMINATION OF CHROMIUM(III) AND CHROMIUM(VI) WITH REVERSED-PHASE ION-PAIR HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A reversed-phase ion-pair high-performance liquid chromatographic method for the simultaneous determination of Cr(III) and Cr(VI) in aqueous solution was developed. Chromium(III) was chelated with ethylenediaminetetraacetic acid (EDTA) prior to the analysis. A C-8 column was used to separate the Cr(III)-EDTA complex from the Cr(VI) ions using an eluent containing acetonitrile and tetrabutylammonium ion. The separated species were monitored at 242 nm using an ultraviolet (UV) detector. The factors affecting complex formation, the chromate stability and prospective interferences were investigated. The proposed method provides a simple analytical procedure for Cr speciation. The detection limits were 0.4 ng for Cr(III) and 1.6 ng for Cr(VI) with a 20 mul injection. The relative standard deviations for Cr(III) and Cr(VI) were 0.24 and 1.78%, respectively.