The application of salicylaldoxime in solvent extraction : Part II. Spectrophotometric determination of copper with 2-(5-nitro-2-pyridylazo)-1-naphthol after separation with salicylaldoxime

A highly sensitive spectrophotometric method for the determination of traces of copper with 2-(5-nitro-2-pyridylazo)-l-naphthol (5N-α-PAN) has been developed. At a pH of 3–4copper(II) is selectively extracted into chloroform as its salicylaldoxime chelate and then stripped into an aqueous acid solution; the pH is adjusted to 9.3, and 5N-α-PAN is added. The 1:2 chelate between copper(II) and the reagent, which promptly precipitates, is extracted into chloroform and measured at 598 nm. The molar absorptivity is 86,000. The application of the method to the analysis of high-purity magnesium and cobalt is described.