A determination of electrode potentials at immobilized liquid membrane interfaces: bipolar effects

Abstract

Electrochemical potentials of redox carriers (Vitamin K 3 and 2 -tert-butylanthraquinone) were determined at the membrane/solution interface. The hydroquinone was generated in a photoelectrochemical cell and the potentials of the quinone/hydroquinone couples were determined at a platinized membrane surface. The values found for the quinone/hydroquinone couples were comparable to the E 1 2 values determined polarographically and exhibited a Nernstian response to the pH of the solution in contact with the membrane. The potentials were shown to be true interfacial membrane potentials, not those of the solution in contact with the membrane. The bipolar effect of having two solutions of differing pH on each side of the membrane was demonstrated by effecting the reduction of a substrate at a higher pH than thermodynamically possible if both solutions were at the same pH.