Mechanism of the carrier-mediated transport of potassium ion across water-nitrobenzene interface by valinomycin

Abstract

The reaction mechanism of the potassium ion transfer from aqueous to nitrobenzene phases, which is facilitated by valinomycin present in the organic phase, was elucidated by polarography at the ascending water electrode and chronopotentiometry at the stationary water electrode. The complex ion is formed in the aqueous phase reaction between potassium ion and valinomycin that migrated from the organic phase. The accumulation of the complex ion in the aqueous phase is controlled by the diffusion of valinomycin from the bulk organic phase to the water-nitrobenzene interface. The distribution of the complex ion accumulated in the aqueous phase is not entirely uniform, but concentrated in a rather narrow layer near the interface. In the presence of the anions having high tendency to ion pair formation, e.g., thiocyanate or iodide ions, in the aqueous phase, the complex ion does not accumulate because of the spontaneous extraction of the ion pair between the complex cation and such anions into the organic phase.