Ion-Partitioning Membrane-Based Electrochemical Sensors

The application of ion-partitioning membranes on proton transducers for the development of electrochemical sensors is presented. The ion-partitioning membrane incorporates two different ionophores, one selective to protons and the other to analyte cations, as well as the necessary anionic lipophilic sites. As dictated by the electroneutrality principle, when the concentration of the analyte cations in the sample increases, the analyte cations are extracted into the membrane, displacing protons of equal charge out of the membrane. The pH-sensitive gate of a CHEMFET or the surface of a glass pH electrode is used as an internal transducer for the monitoring of the membrane proton flux. The resulting signal of the pH transducer is related to the concentration of the analyte cation present in the sample. The experiments presented here indicate that the observed CHEMFET's signal is affected by the interaction of the pH-sensitive sensor element with protons released by the polymeric membrane.