SIMULTANEOUS DETERMINATION OF VANADIUM(IV) AND VANADIUM(V) AS EDTA COMPLEXES BY CAPILLARY ZONE ELECTROPHORESIS

A capillary zone electrophoretic method with on-column UV detection fo r the simultaneous determination of aqueous vanadium(IV) and vanadium( V) ions was studied. Vanadium(IV) and vanadium(V) were chelated with e thylenediaminetetraacetic acid (EDTA) to form anionic VN-EDTA and V(V) -EDTA complexes prior to the analysis. A fused-silica capillary column (100 cmx75 m i.d.) modified with hexadecyltrimethylammonium bromide w as used to separate the V(IV)-EDTA and V(V)-EDTA complexes. A 50 mmol sodium acetate buffer (pH 4.6) containing 0.5 mmol EDTA was used as th e electrolyte. Separation was performed at an applied voltage of -18kV . The separated vanadium species were monitored spectrophotometrically at 280 nm. The electrophoretic behavior of vanadium species was exami ned in detail. Factors that affect the separation of vanadium species, such as running buffer pH, electrolyte concentration, detection wavel ength, EDTA concentration, as well as applied voltage, were systematic ally optimized Calibration graphs were linear over two orders of magni tude with detection limits of 0.1 mu g ml(-1) (V(V)) and 0.4 mu g ml(- 1) (V(IV)). The method was applied to the analysis of a catalyst-leach ate sample.