Solvent extraction-spectrophotometric determination of copper with 2-nitroso-1-naphthol-4-sulfonic acid and quaternary ammonium salt

Abstract

In the solvent extraction system of a metal complex anion with a quaternary ammonium ion, the excess of reagent co-extracted with complex anion into organic phase can be removed from organic phase by adding an adequate amounts of monovalent anion to the extraction system. This principle was applied to the extraction with zephiramine of copper(II) complex anion formed with 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-NW acid). By removing the excess of reagent from organic phase, copper can be determined at the maximum absorption wavelength of the complex(307.5 nm). The molar absorptivity at 307.5 nm was 4.5 × 104 l mol-1cm-1. This method was applied to the determination of copper in iron and steel. The procedure is as follows. Dissolve the sample by heating with aqua regia. Then, evaporate it nearly to dryness. Dilute it with water. Pipette adequate volume of the sample solution into a stoppered test tube. Add ascorbic acid and sodium chloride and extract dichlorocopper(I) ion(CuCl2-) with 5 ml of chloroform solution of zephiramine. Then, shake the organic phase with aqueous solution of hydrogen peroxide and nitroso-NW acid(pH 5) to form copper complex of nitroso-NW acid. By shaking the organic phase with 10 ml of 0.35 M sodium chloride solution(pH9), remove the excess of reagent in the organic phase. Measure the absorbance at 307.5 nm. By the proposed method, copper {(0.06～0.35)%} in NBS iron and steel samples was determined. © 1978, The Japan Society for Analytical Chemistry. All rights reserved.