Highly selective catalytic-spectrophotometric determination of vanadium(v) by using calmagite-bromate redox reaction

A highly selective and sensitive kinetic method for the determination of trace amounts of vanadium(v) is reported. The method is based on catalytic effect of bromate on the oxidation of calmagite in acidic solutions. The reaction is followed spectrophotometrically by measuring the change in absorbance of calmagite at λ = 523 nm using a fixed time method (5 min). Under optimum conditions vanadium can he determined in the range of 2-10 ng ml - 1 . The detection limit based on 3S b criterion was 0.27 ng ml - 1 , and relative standard deviation for ten replicate measurements of 5 ng ml - 1 of V v was 1.2%. Influence of 29 foreign ions were observed. The method was applied for the determination of vanadium in soil samples.