Selective determination of cadmium(II) from divalent metal ions in environmental samples by capillary electrophoresis using in-capillary complexation with a lacunary Keggin-type [PW11O39]7- complex.

A novel capillary electrophoretic (CE) method, based on in-capillary complexation with [PW(11)O(39)](7-), was developed for the determination of cadmium(II) in natural water samples. When a sample solution is injected into a capillary containing 0.20 mM [PW(11)O(39)](7-) and 0.10 M malonate buffer (pH 3.0), the ternary Keggin-type complex, [P(Cd(II)W(11))O(39)](5-), which possesses high molar absorbtivities in the UV region, is formed in the capillary, and its migration toward the anode gives a well-defined migration peak in the electropherogram. An advantage of this method is that many divalent metal ions do not interfere. The proposed method was successfully applied to the determination of Cd(II) in environmental samples. The detection limits were 1 x 10(-7) and 5 x 10(-7) M for river-water and seawater samples, respectively (signal-to-noise ratio = 3).

Simultaneous determination of phosphonate, phosphate, and diphosphate by capillary electrophoresis using in-capillary complexation with Mo(VI).

This study describes the simultaneous determination of phosphonate, phosphate, and diphosphate by CE with direct UV detection, based on in-capillary complexation with Mo(VI). When a mixture of phosphonate, phosphate, and diphosphate was injected into a capillary containing 3.0 mM Mo(VI), 0.05 M malonate buffer (pH 3.0) and 45% v/v CH3CN, three well-defined peaks, due to the migration of the corresponding polyoxomolybdate anions, were separated. The respective calibration graphs were linear in the concentration range of 2 x 10(-6)-2 x 10(-4) M for phosphonate, 1 x 10(-6)-5 x 10(-5) M for phosphate, and 1 x 10(-6)-2 x 10(-4) M for diphosphate; the correlation coefficients were better than 0.9990. The present CE method is successfully applied to the simultaneous determination of phosphonate, phosphate, and diphosphate in tap water.

Simultaneous determination of Zr(IV) and Hf(IV) by CE using precolumn complexation with a [PW(11)O(39)](7-) ligand.

A CE method was developed for the simultaneous determination of Zr(IV) and Hf(IV) at trace levels. A lacunary Keggin-type [PW(11)O(39)](7-) ligand reacted quantitatively with a mixture of trace amounts of Zr(IV) and Hf(IV) to form the so-called ternary Keggin-type anions [P(Zr(IV)W(11))O(40)](5-) and [P(Hf(IV)W(11))O(40)](5-) in 0.010 M monochloroacetate buffer (pH 2.2). Since both ternary anions possessed different electrophoretic mobilities and high molar absorptivities in the UV region, Zr(IV) and Hf(IV) were determined simultaneously with direct UV detection at 258 nm. Each peak height was linearly dependent on the concentration of Zr(IV) or Hf(IV) in the range of 5.0x10(-7)-1.0x10(-5) M; a detection limit of 2x10(-7) M was achieved. The utility of the proposed CE method was demonstrated for the simultaneous determination of Zr(IV) and Hf(IV) in natural water samples with satisfactory results.

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 [PW(11)O(39)](7-) to form the ternary Keggin-type complexes: [P(Sc(III)W(11))O(40)](6-) and [P(Y(III)W(11))O(40)](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 250nm. For both Sc(III) and Y(III), the pre-column method provided linear calibration curves in the range of 2x10(-7) to 1x10(-5)M; the respective detection limits were 1x10(-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.