CATALYTIC PHOTOMETRIC DETERMINATION OF TRACES OF VANADIUM(V) BY THE OXIDATION OF NUCLEAR FAST RED WITH POTASSIUM BROMATE

In a dil. H_2SO_4 solution of pH 2.5~2.9, the oxidation of nuclear fast red by potassium bromate (resulting color-fading of the dyestuff) was catalyzed by the presence of trace amounts of vanadium(Ⅴ). The conditions of the color-fading oxidation reaction were optimized, and the kinetic parameters were also studied. The catalytic oxidation reaction was carried out at 90±0.5 ℃ for 10min. After cooling to room temperature, the absorbances of the catalytic reaction system (A) and of the non-catalytic reaction system (A_0) were measured at (515 nm), using water as the reference solution. Linear relationship between values of lg(A_0/A) and concentration of vanadium(Ⅴ) was found to keep in the range of 0.03~1.5 μg of V(Ⅴ) in 25 mL of solution. Detection limit of the method was found to be 1.9×10~(-6)g·L~(-1). Satisfactory results were obtained in its application to the analysis of some Chinese medicine and some foodstuff samples.