CUPRAC

CUPRAC is a spectrophotometric method used for the quantitative determination of copper. The method relies on the reaction between copper(I) ions and the chromogenic reagent 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, commonly known as Bathocuproine. When copper is in its +1 oxidation state, it forms a stable, intensely colored complex with Bathocuproine. This complex exhibits maximum absorbance at approximately 546 nm.

The procedure typically involves reducing any copper(II) present in the sample to copper(I) using a reducing agent, such as hydroxylamine hydrochloride or ascorbic acid. The colored complex is then formed in a suitable buffer solution, often acetate buffer. The absorbance of the resulting solution is measured using a spectrophotometer at the characteristic wavelength.

The intensity of the color, and therefore the absorbance, is directly proportional to the concentration of copper in the original sample, according to the Beer-Lambert law. A calibration curve is constructed using solutions of known copper concentrations, allowing for the determination of unknown copper levels by comparing their absorbance to the curve. CUPRAC is a sensitive and selective method, making it suitable for analyzing copper in various matrices, including water, biological samples, and alloys. It is widely employed in environmental monitoring, clinical chemistry, and materials science.