Voltammetry of complexes of alkaline and alkaline-earth metals at the interface between two immiscible electrolyte solutions in the presence of dicyclohexyl-18-crown-6

The induced transfer of ions of alkaline and alkaline-earth metals (AAEM) t hrough the water/nitrobenzene interface with use of dicyclohexyl-18-crown-6 (DCH-18-C-6) is studied by the voltammetry technique at the interface betw een two immiscible electrolyte solutions (ITIES). The standard potentials a nd standard energies of the transfer of the complexes, their stoichiometry and stability constants in nitrobenzene are determined. It is found that al l ions form with DCH-18-C-6 complexes MLZ+. Two models of the metal ion tra nsfer induced by the ionophore are discussed: the ionophore distribution mo del and the metal distribution model. It is found that the completeness of a description of the experimental data within one model or another depends on properties of the metal, ionophore, and complex, and on experimental con ditions. Essential requirements for the supporting electrolytes of the aque ous and organic phases are formulated. The factors affecting the selectivit y and assay limit of the voltammetry at ITIES are discussed. Procedures for the voltammetric assay of the potassium and rubidium ions are developed.