Spectrophotometric kinetic determination of copper(II) trace amounts based on its catalytic effect on the reaction of the reduced 2,6-dichlorophenolindophenol and hydrogen peroxide.

A catalytic spectrophotometric method is presented for the determination of Cu(II), based on the oxidation of the leucocompound of the 2.6-dichlorophenolindophenol (DCPI)(r), in the presence of hydrogen peroxide and the catalytic effect of Cu(II) on this reaction in ammonia-ammonium chloride buffer solution of pH 10.5. The above reaction is followed spectrophotometrically at 562 nm. The study was carried out with a filter spectrophotometer equipped with a fiber optic and an immersed type optical cell of 1 cm. The optimum operating conditions regarding concentration of the reagents involved, pH and temperature were established. The interference effect of several metallic species was also investigated. It was found that the proposed method shows fairly good selectivity and sensitivity, simplicity and rapidity compared to other kinetic methods. The working curve of the recommended reaction-rate method is linear in the concentration range 5-300 ng/ml. The relative standard deviation for a standard solution of 30 ng/ml Cu(II) is better than 2.5%. The method was applied successfully on the determination of Cu(II) in a wide variety of real samples such as alloys, pharmaceuticals, foodstuffs and environmental samples. The results were compared to those received with official methods. Good agreement was attained.