CATALYTIC SPECTROPHOTOMETRIC DETERMINATION OF VANADIUM (IV) BASED ON THE OXIDATION OF ALKALI BLUE BY POTASSIUM BROMATE

A simple, rapid and sensitive spectrophotometric method has been proposed for the determination of Vanadium (IV). The method is based on the catalytic effect of V (IV) on the oxidation of Alkali Blue by potassium bromate at pH 4. The rate of decrease in the absorbance of Alkali Blue (at 572 nm) was proportional to the concentration of V (IV) in the range of 100-6000 ng ml -1 . The detection limit was 40 ng ml -1 . The proposed method shows a good selectivity for V (IV) over a wide variety of interference species. It is also valuable in that the presence of a 400 fold excess of V (V) can be tolerable, contrary to many methods for the determination of V (IV) which suffer from severe interference of V (V). This method was successfully applied to the determination of V (IV) in river water, alloy samples and several synthetic samples.