A facile spectrophotometric method for the determination of copper( II) using variamine blue as a chromogenic reagent

Abstract

A rapid and sensitive spectrophotometric method is described for the determination of trace amounts of copper using variamine blue (VB) as a chromogenic reagent. The method is based on the reaction of copper with potassium iodide in acidic medium to liberate iodine, which oxidizes VB to a violet coloured species having λ m a x at 556 nm. Beer's law is obeyed in the range 2-14 μg/ml of Cu. The molar absorptivity and Sandell's sensitivity are found to be 4.31 x 10 3 dm 3 mol - 1 cm - 1 and 1.48 x 10 - 2 μg cm - 2 , respectively. The method has been successfully applied to the determination of copper in alloys and synthetic mixtures.