Determination of Trace Copper in Food with Dual-wavelength and Dual-indicator Catalytic Kinetic Spectrophotometry

A dual-wavelength dual-indicator catalytic kinetic spetrophotometric method for the determination of trace copper was studied. It was based on the catalytic effect of copper on the oxidation of bromocresol purple and neutral red by hydrogen peroxide in NH3-NH4Cl medium at pH=9.65. The absorbance of catalytic system and uncatalytic system were measured at 460 nm and 590 nm,respectively. Under the optimum conditions,the linear range of the determination of trace copper was 0.0060~0.072 μg/mL. The detection limit was 8.0×10-12 g/mL and the relative standard deviation was 2.9% (n=11). The method was applied to the determination of trace copper in flour and rice with satisfactory results.