Microwave assisted spectrophotometric method for the determination of copper using leucocrystal violet

Abstract

A sensitive spectrophotometric method has been developed for the trace determination of copper using leucocrystal violet as chromogenic reagent. The proposed method is based on the reaction of copper(II) with potassium iodide in acid medium to liberate iodine, which oxidizes leucocrystal violet to crystal violet dye having absorption maximum at 590 nm. The reaction between copper and potassium iodide is accelerated by irradiating the mixture with microwave energy for 15 s at 480 W. Beer’s law is obeyed in the concentration range 0.004 – 0.04 µg mL^-1. The molar absorptivity, Sandell’s sensitivity, detection limit and quantitation limit were found to be 1.47 x 10⁶ L mol^-1 cm^-1, 4.3 x 10^-5 µg mL^-2, 0.001 µg mL^-1, 0.0043 µg mL^-1, respectively. The optimum conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination is described. The proposed method has been successfully applied for the determination of copper in environmental samples like tap water, agricultural run off water, plant materials and pharmaceutical samples.

KEY WORDS: Spectrophotometry, Copper determination, Leucocrystal violet

Bull. Chem. Soc. Ethiop. 2007, 21(1), 129-134.