Diversity of ion carrier functions of monensin: A study using voltammetry at the interface of two immiscible electrolyte solutions

Abstract

Sodium and hydrogen ion transfer across the water/nitrobenzene interface in the presence of monensin (HX) was studied using voltammetry at the interface of two immiscible electrolyte solutions (ITIES). Among the monensin species present in the system, HX functions as a sodium carrier and NaX as a proton carrier, the species transferred in both cases being NaHX +. This species is formed in nitrobenzene either by the reaction Na ++HX NaHX + (equilibrium constant log K 1=5.63) or by the reaction H ++NaX NaHX + (equilibrium constant log K 2=9.88). The principal electroneutral process is the exchange reaction Na +(w)+HX(o) NaX(o)+H +(w) (w=water, o=nitrobenzene) with the equilibrium constant log K exch=−4.54.