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 potassi um bromate at pH 4.2 and 30 degrees C. The reaction was monitored spectrofl uorimetrically by measuring the decrease of fluorescence intensity of azome thine-H (lambda(ex) = 382 nm, lambda(em) = 422 nm) after a fixed time (4 mi n) and used EDTA to stop the reaction. The fluorescence decrease varies lin early 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 m L(-1) (SD=0.00038 for 15 times measurements), respectively. The detection l imit of the method was down to 6.914 x 10(-5) mu g mL(-1). The effect of fo reign ions was studied and the method was found free from interference exce pt Fe3+. The proposed method was successively applied to determine vanadium (V) in natural water.