2-ニトロソ-5-ジメチルアミノフェノールとゼフィラミンを用いる銅の溶媒抽出-吸光光度定量

2-Nitroso-5-dimethylaminophenol (nitroso-DMAP) reacts with copper(II) ion to form a 1:2 complex in an aqueous solution. In the presence of zephiramine (tetradecyldimethylbenzylammonium chloride), a 1:3 complex is formed and can be extracted into chloroform. The excess of nitroso-DMAP co-extracted with complex anion into organic phase can be removed by adding an adequate amount of chloride ion at about pH 12. Maximum absorption wavelength of the copper complex in the organic phase is 468 nm, at which the molar absorptivity was found to be 3.6×10(4) l mol(-1) cm(-1). This method was applied to determine micro amounts of copper in iron and steel samples and aluminium alloys. The procedure is as follows. An adequate amount of the sample was dissolved in aqua regia. The resulting solution was evaporated nearly to dryness. The residue was re-dissolved in distilled water to give an adequate volume. Five milliliters of the sample solution were taken into a stoppered test tube. Ascorbic acid and potassium chloride solutions were then added. Dichlorocopper(I) ion was extracted with chloroform solution of zephiramine. The organic phase was shaken with an aqueous solution containing hydrogen peroxide, nitroso-DMAP, potassium chloride, and potassium hydroxide to form the copper complex of nitroso-DMAP and to remove the excess of reagent in the organic phase. The absorbance at 468 nm was measured against the reagent blank.