Solvent extraction studies of metal 1,10-phenanthroline complexes
Asamoah, Rose L.
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The use of 1,10-phenanthroline as an extraction reagent for the separation of metal ions has been investigated. It was found that a large number of different metal ions can be chelated by 1,10-phenanthroline and extracted into certain immiscible solvents in the form of chelate salts or ion-association species formed from the chelate complex and appropriate anions. Various extraction solvents, anions, and solution conditions were evaluated to determine optimum procedures and conditions for quantitative separations of some metal ions by solvent extraction. Distribution ratios were measured as a function of hydrogen ion, anions, and excess 1,10-phenanthroline concentrations for zinc, cadmium and lead. An investigation of the extraction mechanism demonstrated that zinc, cadmium and lead ions are extracted by nitrobenzene in the form of tris-1,10-phenanthroline metal(II) perchlorate salts. Over the pH range from 3 to 7 extraction is quantitative, provided that a slight excess of 1,10-phenanthroline and perchlorate concentration of at least 0.1 M? are employed. Using the conditions and procedure found best for extraction of zinc, cadmium and lead, the distribution ratios of a variety of other metal ions were measured. The results indicate that 1,10-phenanthroline can be used to good advantage as an extraction reagent for group separations. It is especially useful as a means of concentrating trace metal constituents prior to their determination by flame spectroscopy, thereby enhancing the sensitivity of the determinations. It was found that nitrobenzene, in addition to serving as a highly efficient extraction solvent for metal chelates of 1,10-phenanthroline, has the added advantage of serving as a suitable solvent for direct aspiration into an acetylene-air flame for spectrophotometric determination of metal ions.