Determination of chromium(III) and chromium(VI) using suppressed ion chromatography inductively coupled plasma mass spectrometry

We have developed a method for the determination of Cr(III) and Cr(VI) by ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) using a self-regenerating suppressor. Deposition of the dissolved solids on the cones and the ion optics was eliminated by the Suppressor. Chromium(III) Wits derivatized with EDTA, forming a stable mono-anionic complex, which wits then separated from Cr(VI) by anion-exchange chromatography. The conditions for the quantitative conversion or Cr(III) to the corresponding EDTA complex were optimized and neither oxidation of Cr(III) to Cr(VI) nor reduction Or Cr(VI) to Cr(III) were observed. Using 50 mmol L-1 NH4NO3 (pH 8) as the chromatographic eluent, potential interferents, Such as chloride, carbonate and sulfate, were separated from both the Cr(EDTA) complex and from Cr(VI), and no salt deposition was observed over long periods of time. The tolerance of the method to the presence of major matrix anions (NO3-, Cl-, CO32- and SO42-) was extensively studied. With it 1 mL injection volume. the detection limits were 5 and 12 ng L-1 using Cr-52, and 7 and 16 ng L-1 using Cr-53 for Cr(III) and Cr(VI). respectively. The RSD of 5 injections was less than 5% at the 50 ng L-1 level. The method was validated using reference materials SRM 1643d and SLEW-3.