PRACTICAL LIMITS FOR SOLID-STATE REFERENCE ELECTRODES

A solid-state reference electrode is defined as any material in direct contact with the test solution that maintains a constant or predictable interfacial potential difference despite changing type and concentration of chemical species in the test electrolyte. The practical conditions under which an interfacial potential is expected to be invariant are studied, and it is shown that for equilibrium the interfacial potential remains constant only when all the ionic partition coefficients are equal. More exotic non-equilibrium reference electrode interfaces may also be realized, but pose additional problems.