Abstract:

With the activation of p-phenanthroline, potassium bromate oxidized methyl violet fading reaction catalyzed by copper (II) was investigated, and a new catalytic discoloring spectrophotometry for determining trace copper was proposed. The effects of acidity, reagent dosage, reaction temperature, reaction time, surfactant and coexisting ions on the reaction were discussed and the optimal conditions were investigated. After reaction at 72 ℃ for 15 min in a 25 ml volumetric flask, the calibration curve was drawn for the relationship of absorbance difference between copper (II) containing solution and non-copper (II) containing solution with copper (II) mass concentration, and then the content of trace copper (II) was determined by the absorbance difference. The detection wavelength of this method was 578 nm, the linear range was between 2.4×10-3 and 5.12× 10-2 μg/ml, and the detection limit was 2.4×10-6 g/L. When this method was applied to the determination of copper in green tea, wheat flour, rice, milk powder, and dried kelp, the maximum relative standard deviation was 4.22%, and the spike recoveries were 96.0% to 104.0%.

Key words: catalytic spectrophotometry, p-phenanthroline, potassium bromate, methyl violet, copper