Catalytic spectrophotometric determination of molybdenum

A highly selective, sensitive, and simple catalytic method for the determination of molybdenum in natural and waste waters was developed. It is based on the catalytic effect of Mo(VI) on the oxidation of 2-aminophenol with H2O2. The reaction is monitored spectrophotometrically,by tracing the oxidation product at 430 nm after 10 min of mixing the reagents. Addition of 800 mug . cm(-3) EDTA conferred high selectivity; however, interfering effects of Au(III), Cr(III), Cr(VI), and Fe(III) had to be eliminated by a reduction and co-precipitation procedure with SnCl2 and Al(OH)(3). Mo(VI) shows a linear calibration graph up to 11.0 ng . cm(-3); the detection limit, based on the 3S(b)-criterion, is 0.10 ng . cm(-3). The unique selectivity and sensitivity of the new method allowed its direct application to the determination of Mo(VI) in natural and waste waters.