Analytical Sciences

Simultaneous Determination of Chromium(VI) and Chromium(III) by Capillary Electrophoresis

Sadayuki HIMENO* * , Yoichi NAKASHIMA** and Ken-ichi SANO*

*Department of Chemistry, Faculty of Science, Kobe University, Nada, Kobe 657, Japan
**Technology Research Institute of Osaka Prefecture, Izumi, Osaka 590-02, Japan

A simple and sensitive method was developed for the capillary electrophoretic determination of Cr(VI) and Cr(III). In a 0.1 M CClH2COOH-CClH2COONa buffer of pH 2 - 3, Mo(VI) reacts rapidly, even at room temperature with Cr(III), to form a stable heteropolyanion. Both anionic forms of Cr(III) and Cr(VI) can be determined simultaneously by capillary electrophoresis with UV detection at 256 nm. Linear calibration curves were obtained in the concentration ranges of 5´±0 -6 - 1´±0 -4 M and 1´±0 -5 - 1´±0 -4 M for Cr(III) and Cr(VI), respectively; the detection limits were 2´±0 -6 and 5´±0 -6 M (the signal-to-noise ratio=5). Interference from foreign ions is also discussed. (Keywords: Capillary electrophoresis, hexamolybdochromate complex, oxidation state analysis, chromium)

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