Kinetic spectrophotometric determination of trace copper(II) ions by their catalytic effect on the reduction of brilliant cresyl blue by ascorbic acid

In the present study, a novel catalytic-kinetic spectrophotometric method was developed for the determination of trace amounts of copper. It is based on the catalytic effect of Cu(II) on the reduction of brilliant cresyl blue (BCB) by ascorbic acid in pH 5.0 acetate buffer medium. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of BCB at 624 nm. The operating conditions regarding concentration of reagents, pH, time, and temperature were established and optimized in detail. The working curve was linear in the concentration range of 0.1-5.0 μg L−1 . The maximum percentage error and standard deviation for 5 replicate determination of the 3 μg L−1 Cu(II) were 3.20 and 0.45, respectively. The detection limit and quantification limit were 0.025 and 0.086 μg L−1 , respectively. The procedure was successfully applied to determination of dissolved copper levels of 3 different natural spring waters and artificially prepared wastewater samples. The accuracy of the proposed kinetic method was tested by means of 5 replicate analyses of the certified standard materials, SRM 1640, based on 2 independent methods.