Abstract
A novel, highly sensitive, simple, and selective kinetic method was developed for the determination of vanadium based on its catalytic effect on the oxidation of 2,3,4-trihydroxybenzoic acid with bromate. The reaction was followed spectrophotometrically by tracing the oxidized product at 412 nm after 30 min of mixing the reagents. The optimum reaction conditions were 1.8 mmol dm(-3) trihydroxybenzoic acid, 60 mmol dm(-3) bromate, and 50 mmol dm(-3) dichloroacetate buffer of pH 1.50 +/- A 0.02 at 30 A degrees C. Addition of 5 mmol dm(-3) citric acid enhanced the selectivity of the proposed method. Following the recommended procedure, vanadium [(V) and (IV)] can be determined with a linear calibration graph up to 0.60 mu g dm(-3) and a detection limit, based on the 3S(b) criterion, of 0.011 mu g dm(-3). The high sensitivity and selectivity of the proposed method allowed its direct application to the determination of vanadium [(V) and (IV)] in rain water, rice, and wheat samples. The method was validated by comparison with a reference extraction ICP-OES method along with recovery experiments. Moreover, published catalytic-spectrophotometric methods for the determination of vanadium from the past decade were reviewed.