Fundamental studies of carrier based potentiometric ion sensors

Carried based potentiometric ion sensors have been established as a major class in the field of potentiometric sensors. Fundamental issues regarding these sensors, such as response mechanisms, selectivities, and reference electrodes are important for sensor design. A better understanding of these issues could lead to revolutionary improvement of sensor performance. For this purpose, this dissertation will focus mainly on fundamental topics related to the development of carrier based potentiometric ion sensors. These include the studies of pH electrodes based on electrically charged carriers, the selectivity of ionophore-based liquid membrane electrodes, the in-situ determination of the binding properties of ionophores in plasticized polyvinyl chloride (PVC) membranes, and reference electrodes based on hydrophobic membranes.; In Chapter 2, the effect of salt additives on the potentiometric response of solvent polymeric membrane pH electrodes based on an electrically charged carrier, 4'5'-dibromofluorescein octadecylester (ETH 7075) is reported. The response behavior is explained qualitatively on the basis of the phase boundary potential model.; In Chapter 3, we characterize a new kind of solvent polymeric pH electrodes based on electrically charged carriers. Potentiometric responses of these sensors are predicted with a simplified phase boundary potential model.; In Chapter 4, we investigate the influence of lipophilic salts without ion-exchanger properties on the selectivity of ionophore-based liquid membrane electrodes. Theoretical predictions are confirmed with Ca2+-responsive membranes containing the ionophores ETH 2120, ETH 1001, and ETH 129.; In Chapter 5, a potentiometric: method to determine ionophore complex formation constants in solvent polymeric membrane phases is described. Five ionophores, valinomycin, BME-44, ETH 2120, tert-butylcalix[4]arene tetraethylester, and S,S'-methylenebis(diisobutyldithiocarbamate) that have already been characterized with other established methods are characterized in this study.; In Chapter 6, four methods that can be used to determine the binding properties of ionophores directly in the sensing membrane are discussed and compared. Principal advantages and drawbacks of each method are outlined, and results are shown for each method involving the potassium ionophore valinomycin.; In Chapter 7, we report on a successful application of the newly established potentiometric method described in chapter 5 based on segmented sandwich membranes to determine the binding properties of ETH 5294 in solvent polymeric membranes.; In Chapter 8, we explore the possibility of using plasticized poly(vinyl chloride) membrane electrodes containing an ion-exchanger in solutions of a polyanionic anticoagulant as reference electrodes without a liquid junction.