Improvement on simultaneous determination of chromium species in aqueous solution by ion chromatography and chemiluminescence detection

A sensitive method for the simultaneous determination of chromium(III) and chromium(VI) was developed using ion chromatography and chemiluminescence detection. Two Dionex ion-exchange guard columns in series, CG5 and AG7, were used to separate chromium(III) from chromium(VI). Chromium(VI) was reduced by potassium sulphite, whereupon both species were detected by use of the luminol–hydrogen peroxide chemiluminescence system. Parameters affecting retention times and resolution of the separator columns, such as eluent pH, eluent composition, reductant pH and concentration, and flow rates were optimized. Furthermore, the stabilities of reductant and luminol solutions were studied. The linear range of the calibration curve for chromium(III) and chromium(VI) was 1–400 μg l−1. The detection limit was 0.12 μg l−1 for chromium(III) and 0.09 μg l−1 for chromium(VI), respectively. The precision at the 20 μg l−1 level was 1.4% for chromium(III) and 2.5% for chromium(VI), respectively. The accuracy of the chromium(III) determination was determined by analysis of the NIST standard reference material 1643c, Trace elements in water with the result 19.1±1.0 μg Cr(III) l−1 (certified value 19.0±0.6 μg Cr(III) l−1). The method was applied to analyse the stability of chromium patches for contact dermatitis testing.