Catalytic quenching spectrofluorimetric determination of trace amounts of vanadium(V) based on its catalytic effect on the azomethine-H-bromate reaction

A catalytic quenching spectrofluorimetric method for the determination of V(V) using azomethine-H as a luminescence reagent has been investigated due to the catalytic effect of V(V) ion on oxidation of azomethine-H by potassium bromate at pH 4.2 and 30 degrees C. The reaction was monitored spectrofluorimetrically by measuring the decrease of fluorescence intensity of azomethine-H (lambda(ex) = 382 nm, lambda(em) = 422 nm) after a fixed time (4 min) and used EDTA to stop the reaction. The fluorescence decrease varies linearly with the concentration of vanadium(V) in the range 5.0 x 10(-4)-0.022 mu g mL(-1) (SD=0.00029 for 10 times measurements), and 0.025-0.060 mu g mL(-1) (SD=0.00038 for 15 times measurements), respectively. The detection limit of the method was down to 6.914 x 10(-5) mu g mL(-1). The effect of foreign ions was studied and the method was found free from interference except Fe3+. The proposed method was successively applied to determine vanadium(V) in natural water.