SIMULTANEOUS DETERMINATION OF CHROMIUM(III) AND CHROMIUM(VI) BY ION CHROMATOGRAPHY WITH INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

A combined system of inductively coupled plasma mass spectrometry (ICP-MS) with ion chromatography (IC) was used for the speciation of the chromium (Cr) species. After chelation with ethylenediaminetetraacetic acid (EDTA), Cr(III) and Cr(VI) were separated by anion-exchange chromatography. Subsequently, eluates from a separation column were directly introduced into the ICP-MS and detected at m/z 52 and 53. Separation parameters were optimized for the chromium species. Excelpak ICS-A23 (75 x 4.6 mm I.D.) packed with hydrophilic polymer based anion-exchange resin (ion-exchange capacity: 0.05 mequiv. g(-1) dry weight) was used as separation column and 1.0 . 10(-3) M EDTA-2NH(4)-0.01 M oxalic acid (pH 7.0) was used as a mobile phase. Cr(III) and Cr(VI) were completely separated within 8 min without any interference of ArC+ and ClO+. Detection limits (S/N = 3) for Cr(III) and Cr(VI) were 8.1 . 10(-5) and 8.8 . 10(-5) mg Cr/l, respectively. The linear range was 4 orders of magnitude, from 0.5 . 10(-3) to 5 mg Cr/l. With regard to reproducibility, R.S.D. (n = 5) was better than 2.5%. The developed IC-ICP-MS method was applied to the determination of the chromium species and metal elements in water.