Spectrophotometric reaction rate method for the determination of trace amounts of vanadium(V) by its catalytic effect on the oxidation of Nile Blue with bromate

A kinetic spectrophotometric method for the determination of trace amounts of vanadium(V) is described. It is based on the catalytic action of this io n on the oxidation of Nile Blue by bromate, which yields a colorless produc t in acidic media. The reaction is followed spectrophotometrically by measu ring the rate of decrease in absorbance at 585 nm and 30 degrees C. A fixed time method of 4.0 min from initiation of the reaction was used. Vanadium( V) in the range of 0.004-0.520 mu g/ml can be determined. The proposed meth od is hardly subject to interference. The parameters affecting the sensitiv ity were optimized The proposed method was used for the determination of va nadium in water and in milk samples.