Ion carrier properties of nigericin studied by voltammetry at the interface of two immiscible electrolyte solutions

Abstract

Alkali metal and hydrogen ion transfer across the water/nitrobenzene interface facilitated by nigericin (HX) was studied using voltammetry at the interface of two immiscible electrolyte solutions. In acidic media the free acid, HX, functions as an alkali metal ion (M+) carrier while in a neutral medium the complex MX becomes a proton carrier. The stability constants in nitrobenzene, K1,MHX  [MHX+]/[M+][HX], increase in the sequence Li+ ⪡ Cs+ < Rb+ ⪡ Na+ < K+. For K+ and Na+ the constants of the equilibria MX + H+ ⇄ MHX+ (in nitrobenzene), M+ (w)+HX(o) ⇄ MX(o)+H+ (w)(w denoting water, o nitrobenzene) and M+ + X- ⇄ MX (in nitrobenzene, only the ratio KKX/KNaX have also been determined.