Simultaneous electrophoretic determination of vanadium(V) and vanadium(IV) based on the complex formation with a Mo(VI)-P(V) reagent.

A capillary electrophoretic (CE) method was developed for the sensitive determination of V(V) and V(IV). A Mo(VI)-P(V) reagent reacted with a mixture of trace amounts of V(V) and V(IV) to form the [P(V(V)Mo(11))O40]4- and [P(V(IV)Mo11)O40]5- complexes in 0.1 M monochloroacetate buffer (pH 2.2). Since the V-substituted Keggin anions possessed high molar absorptivities in the UV region and the peaks due to their migrations were well separated in the electropherogram, the pre-column complex formation reaction was applied to the simultaneous CE determination of V(V) and V(IV) with direct UV detection at 220 nm. The calibration curves were linear over two orders of magnitude with detection limits of 5 x 10(-7) M for V(V) and 2 x 10(-7) M for V(IV).