Catalytic determination of vanadium using the perphenazine–bromate redox reaction and a citric acid activator

Abstract

Citric acid was found to have a highly activating effect on the vanadium-catalysed oxidation of perphenazine (PP) with bromate. An extremely sensitive, selective and simple method was developed for the determination of vanadium based on this effect. The reaction rate was followed spectrophotometrically by monitoring the formation of the red oxidation product of PP at 526 nm within 1 min of mixing. Using the recommended procedure, vanadium can be determined up to 6.5 ng ml^–1 with a linear calibration graph and a detection limit of 0.08 ng ml^–1. A suggested mechanism of the reaction and the activating mechanism of citric acid is presented. The method surpassed the standard Fishman–Skougstad catalytic method in sensitivity, selectivity and speed and was successfully applied to the determination of vanadium in polluted river waters.