Determination of Trace Copper(II)by Catalytic Kinetic Spectrophotometry with Alanine as the Sensitizer

A new catalytic kinetic spectrophotometry for the determination of trace copper was established.The method was based on the catalytic effect of copper on the oxidizing discoloring reaction of Evans blue with hydrogen peroxide in HAc-NaAc buffer solution at pH=4.7.The apparent activation energy and the rate constant of the reaction were 12.29kJ/mol and 3.25×10-4 s-1, respectively.Under the optimized conditions,the absorbance showed good linearity with the concentration of Cu2+in the range of 0.008～0.120μg/mL.The regression equation wasA=2.6069c-0.0123,the correlation coefficient was 0.9999,and the detection limit of this method was 5.75×10-9 g/mL.The proposed method has been used to analyze Cu2+in several samples,such as water samples, tea and fresh vegetables with RSD less than 0.61%.