Influence of Anion Doped Polypyrrole Film as Ion-to-Electron Transducer on the Response Performance of Internal Solid Contact Potentiometric Sensors

Abstract

The internal solid contact potentiometric sensors (ISCSs) based on the use of conducting polymers (e.g. polypyrrole (PPy), polyaniline(PAn) etc.) as inner contact ion-to-electron transducer material and ion-selective polymeric membrane as the ion sensing membrane possess pronounced potential stabilities, in comparison with the coated wire electrodes. Furthermore, the response performances of ISCS are mainly dependent on the composition of the polymeric sensing membrane including the types of ionophore, plasticizer, ionic additives, and their mass percentages. This study is focused on investigating experimentally whether there is a negligible effect of an anion doped within PPy film for an ISCS on the response performances of the sensor or not. Five anions including Cl−, , SCN−, ClCH2COO− and Cl3CCOO− were used as the doped anions and five types of ion exchanger were used as the electroactive substances in the ion-selective PVC membranes to fabricate these sensors. The results indicate that the nature of dopant can influence the response behaviors, such as detection limit, response slope and potential selectivity, of the ISCSs to some extent, which are dependent on the type of primary ion tested. The size and lipophilicity of dopant in PPy layer could be important factors influencing response performances of an ISCS. The origin of the influences has been discussed from models proposed in this paper.