Kinetic spectrophotometric determination of trace vanadium in foodstuff based on oxidation discoloration of methyl violet with potassium bromate

Based on the catalytic effect of trace amount vanadium(Ⅴ) on oxidation of methyl violet by potassium bromate in 0.004 mol/L citric acid solution,a new kinetic spectrophotometric method for the determination of trace amount vanadium(Ⅴ) has been developed.The detection limit is 1.23 μg/L and the linear range of determination is 0.0-0.16 μg/mL for vanadium(Ⅴ).The relative standard deviation for the determination of vanadium(Ⅴ) at the concentration of 2.0 μg/25 mL is calculated to be 1.9%(n = 11).The factors such as acidity,concentrations of reactants,reactive time,temperature,influence of coexisting ions on the reaction and the optimum reaction conditions of the reaction were determined.The method has been applied to the determination of trace amount vanadium(Ⅴ) in wheat and apple samples with the relative standard deviations of 1.1% ～ 2.7% and the recoveries of 97.6% ～ 99.0%.