Plasticizer-free all-solid-state potassium-selective electrode based on poly(3-octylthiophene) and valinomycin

All-solid-state potassium-selective electrodes with plasticizer-free membranes were prepared by incorporation of valinomycin as the ionophore and potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate as the lipophilic additive in a semiconducting conjugated polymer matrix of poly(3-octylthiophene). The membrane components were dissolved in chloroform and deposited on glassy carbon by solution casting resulting in all-solid-state potassium sensors. The analytical performance of the potassium sensors were studied by potentiometric measurements. Electrochemical impedance spectroscopy was used to obtain information about the charge transfer and double layer charging processes in the electrodes. The results show that a plasticizer-free all-solid-state potassium-selective electrode can he prepared and that the electron transfer at the glassy carbon/membrane interface plays a significant role in the signal transduction. (C) 1999 Elsevier Science B.V. All rights reserved.