Absorption Ratio-Spectrophotometric Determination of Trace Amounts of Copper(Ⅱ) in Surface Water by the Color Reaction with Dibromo Alizarin Violet

In an acetate buffer medium of pH 6.35,a binary coordination complex of Cu(DBAV)2 was formed by the reaction of Cu(Ⅱ) with dibromo alizarin violet (DBAV),and its molecular structure was characterized by the spectral correction method. Wavelengths of the crest and trough in the absorption spectrum of the coordination complex were found at 607 nm and 548 nm respectively. Values of absorbance of the colored complex solution and the blank solution were measure at both wavelengths (recorded as A607 nm,A548 nm and A′607 nm and A′548 nm) and value of difference of absorption ratio (ΔAr) was calculated. Linear relationship between values of ΔAr and concentration of Cu(Ⅱ) ion was found in the range within 0.15 mg·L-1,and the detection limit (3σ) found was 2.5 μg·L-1. The proposed method was used in the determination of trace amount of copper(Ⅱ) in surface water taken from Yangtze River and Huangpu River,giving results in consistency with the results found by ICP-AES method,and the values of recovery found were ranged from 100% to 108%.