Voltammetric study on the transfer of alkali and alkaline earth metal ions at the aqueous/organic interface facilitated by phosphine oxides

The transfer of alkali metal and alkaline earth metal ions (Mz) from aqueous to nitrobenzene (NB) phases, facilitated by mono-, bi-, or tridentate phosphine oxides (PO), was investigated in terms of the voltammetry for the ion transfer across the interface of two immiscible electrolyte solutions. The complex formation of Mz with PO in the vicinity of the interface and the transfer process of Mz were clarified based on an analysis of the current-potential curves, while referring to information obtained from the synergistic ion-pair extraction of Mz(ClO4−)z with PO. The stability constants of Mz–PO complexes in NB were evaluated based on the half-wave potentials in the ion transfer voltammograms, and were related to the properties of Mz and PO.