Simultaneous capillary electrophoretic determination of Sb(III) and Bi(III) based on the complex-formation with a W(VI)–P(V) reagent

A capillary electrophoretic method was developed for the simultaneous determination of Sb(III) and Bi(III). A 1.0 mM W(VI)–0.10 mM P(V) complexing reagent readily reacted with a mixture of trace amounts of Sb(III) and Bi(III) to form the corresponding ternary Keggin-type complexes; [P(SbIIIW11)O40]6− and [P(BiIIIW11)O40]6− in 0.01 M malonate buffer (pH 2.4). Since the peaks due to the migrations of the ternary complex anions were well separated in the electropherogram, the pre-column complex-formation reaction was applied to the simultaneous CE determination of Sb(III) and Bi(III) with direct UV detection at 255 nm. The calibration curves were linear in the range of 2×10−7–5×10−5 M; a detection limit of 1×10−7 M was achieved for Sb(III) or Bi(III) (the signal-to-noise ratio=3).