Dependence of the potentiometric response of PEDOT(PSS) on the solubility product of silver salts

•Cationic/anionic response of GC/PEDOT/PSS depends on the conditioning in Ag.•Cationic response in salts where anions do not form sparingly soluble silver salts.•Anionic response in salts where anions do form sparingly soluble silver salts.•Close to nernstian cationic response for GC/PEDOT/PSS/K-ISM.•Excellent agreement with thermodynamic data. The potentiometric response of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) deposited on glassy carbon (GC), i.e. GC/PEDOT(PSS), was studied before and after conditioning in silver nitrate solution. The deposition of silver in the PEDOT(PSS) film was characterized by SEM/EDAX and cyclic voltammetry. The potentiometric response of the Ag-conditioned GC/PEDOT(PSS) electrode was dependent on the nature of the anion present in the calibration solutions. In cases where anions do not form sparingly soluble silver salts, a cationic response was observed for GC/PEDOT(PSS), as expected. However, an anionic response was observed in solutions containing anions (X−) that can form sparingly soluble salts with silver ions (AgX). Furthermore, the measured potentials in X− solutions followed the solubility product values of AgX. The agreement between the experimental and thermodynamic data was excellent. This validates the hypothesis of equilibrium existing between Ag+ ions in the polymer film (due to conditioning) and Ag+ ions in the solution. The Ag-conditioned GC/PEDOT(PSS) electrode covered with a potassium ion-selective membrane (GC/PEDOT(PSS)/K+-ISM) showed a cationic response in KCl solutions with close to Nernstian slope value. [Display omitted]