Electrochemical control of the standard potential of solid-contact ion-selective electrodes having a conducting polymer as ion-to-electron transducer

This work addresses the well-known problem of variations in the standard potential (E degrees) of solid-contact ion-selective electrodes (SC-ISEs) that have a conducting polymer (CP) as ion-to-electron transducer covered by a polymeric ion-selective membrane. Poly(3,4-ethylene dioxythiophene) doped with poly(sodium 4-styrenesulfonate), i.e. PEDOT(PSS), was electrodeposited on glassy carbon (GC) disk electrodes and used as the solid contact for three different types of PVC-based membranes in order to elucidate the possibility to electrochemically control E degrees for this type of SC-ISE. The GC/PEDOT(PSS) electrode was thus coated with potassium-selective membranes with and without the lipophilic salt tetradocedylammonium tetrakis(4-clorophenyl)borate (ETH-500) and by a cation-sensitive membrane without ionophore. The results show that the standard potential of the studied types of SC-ISEs can be shifted by applying a potential that deviates from the open-circuit potential of the electrode in the chosen electrolyte solution or by applying current pulses in the nA range.