DETERMINATION OF COBALT(II) BY REVERSED-PHASE LIQUID-CHROMATOGRAPHY WITH ELECTROCHEMICAL AND SPECTROPHOTOMETRIC DETECTION

A reversed-phase liquid chromatographic method for the selective and s ensitive determination of cobalt (II) with ethyl xanthate (EX) is desc ribed. The method is based on the pre-column derivatization of cobalt( III)-EX chelate, injection of the sample onto a C-18 column, and eluti on with 4:1 acetonitrile/sodium acetate solution (0.02 mol dm(-3), pH 7.8) containing 0.02 mol dm(-3) potassium nitrate as the mobile phase. The detection of the metal in eluate has been made by electrochemical (at +1.40 V vs. Ag/AgCl) and spectrophotometric (at 330 nm) methods. The detection limits (S/N=3) for cobalt(II) by the proposed method are 0.23 and 0.56 mu g dm(-3) for the electrochemical and spectrophotomet ric detection, respectively. Cobalt in pepperbush has been determined with satisfactory precision.