Extractive separation and spectrophotometric determination of nickel(II) with dithizone and 1, 10-phenanthroline

Abstract

A highly selective method was developed for the separation of nickel(II) from manganese(II), cobalt(II), copper(II), zinc(II), cadmium(II), mercury(II), silver(I) and lead(II) with a mixture of dithizone and 1, 10-phenanthroline by employing the back-extraction technique. The established procedure is as follows: Adjust the pH of a sample solution to ca. 8.5 by adding nitric acid or ammonia, and add 20 cm³ of chloroform containing 0.02% dithizone. Shake the mixture for 30 min, and allow the phases to separate.Transfer 15 cm³ of the organic phase to another separatory funnel containing an equal volume of an aqueous nitric acid solution of pH 1.5. Extract manganese(II), zinc(II), cadmium(II) and lead(II) into the aqueous phase by shaking the mixture for 30 min.Take 10 cm³ aliquot of the organic phase into another separatory funnel containing 20 cm³ of an aqueous solution of pH 1.5, and add 10 cm³ of chloroform olution of 0.002 mol dm^-3 1, 10-phenanthroline. Then, shake the mixture for 30 min. The resulting aqueous phase contains only nickel(II). For the determination of nickel(II), take an aliquot of the aqueous phase, and adjust the pH to ca. 11.5 by adding ammonia. Add 10 cm³ of chloroform containing 0.001% dithizone and 0.02 mol dm^-3 1, 10-phenanthroline and shake the mixture for 10 min. Measure the absorbance of the organic phase at 514 nm against the reagent blank. Beer's law is obeyed and the molar absorptivity is 49500 dm³mol^-1cm^-1. Recovery of nickel(II) was 96% in the presence of each 20μg of cobalt(II), copper(II), zinc(II) and cadmium(II). Iron(II) (≤100μg) can be masked with tartrate. A. large amount of iron(III) should be removed preliminarily by MIBK extraction.