Simultaneous capillary electrophoretic determination of Sc(III) and Y(III) based on the complex-formation with a lacunary Keggin-type [PW11O39]7− complex

Trace amounts of Sc(III) and Y(III) can react with [PW11O39]7− to form the ternary Keggin-type complexes: [P(ScIIIW11)O40]6− and [P(YIIIW11)O40]6− having high molar absorptivities in the UV region. Since the rate of the complex-formation was very rapid and the kinetically stable ternary anions migrated in the capillary with different electrophoretic mobilities, the complex-formation reaction was applied to the simultaneous CE determination of Sc(III) and Y(III) with direct UV detection at 250 nm. For both Sc(III) and Y(III), the pre-column method provided linear calibration curves in the range of 2 × 10−7 to 1 × 10−5 M; the respective detection limits were 1 × 10−7 M (the signal-to-noise ratio = 3). The proposed method was successfully applied to the determination of Sc(III) and Y(III) in river water.