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A Novel Chromogenic Scheme for the Determination of Cu(II) in Water Samples

Abstract In the present study, a novel chromogenic scheme for the determination of copper(II) using thiocyanate and variamine blue has been proposed. The proposed spectrophotometric method is based on the reaction of copper(II) with potassium thiocyanate which leads to the formation of thiocyanogen. The thiocyanogen formed subsequently oxidizes variamine blue to violet coloured dye cation which gives maximum absorbance at 550 nm. Beer’s law was obeyed in the concentration range 0.05-7.0 µg mL-1. The detection limit and quantification limit were found to be 7.8×10-3 μg mL-1 and 2.3×10-2 μg mL-1 respectively, for the coloured system. The molar absorptivity and Sandell’s sensitivity were found to be 6.646×103 L mol-1cm-1 and 9.5×10-3 μg cm-2, respectively. The effect of reagent concentration, pH, time, temperature on the color reaction were investigated and the required conditions for the method were optimized. The effect of various interfering species were also studied, and it was found that most of the ions did not interfere. The method is simple, rapid, cost-effective, comparably sensitive, highly selective, non-extractive, does not involve any tedious synthetic step and the recommended procedure has good accuracy and precision. The method was successfully applied for the determination of copper in different water sample and recovery percentage was found to be between 97.0 % to 99.4 % for different environmental matrices. GRAPHICAL ABSTRACT