Highly sensitive catalytic determination of molybdenum.

A novel, highly sensitive, selective, and simple kinetic method was developed for the determination of Mo(VI) based on its catalytic effect on the oxidation of 1-amino-2-naphthol-4-sulfonic acid (ANSA) with H(2)O(2). The reaction was followed spectrophotometrically by tracing the oxidized product at 465nm after 30min of mixing the reagents. The optimum reaction conditions were: 10mmol l(-1) ANSA, 50mmol l(-1) H(2)O(2), 100mmol l(-1) acetate buffer of pH 5.0+/-0.05 and at 40 degrees C. Addition of 200microg ml(-1) diethylenetriaminepentaacetic acid (DTPA) conferred high selectivity for the proposed method. Following the recommended procedure, Mo(VI) could be determined with a linear calibration graph up to 2.5ng ml(-1) and a detection limit, based on the 3S(b)-criterion, of 0.027ng ml(-1). The unique sensitivity and selectivity of the implemented method allowed its direct application to the determination of Mo(VI) in natural and industrial waste water. The method was validated by comparison with the standard ETAAS method. Moreover, published catalytic-spectrophotometric methods for the determination of molybdenum were reviewed.