Towards potentiometric detection in nonaqueous media: Evaluation of the impacts of organic solvents on polymeric membrane ion-selective electrodes.

Polymeric membrane ion-selective electrodes (ISEs) have been widely used in various fields including clinical diagnosis, environmental monitoring and industrial analysis. Although most samples of analytical interest measured by the ISEs are aqueous solutions, the applications of these electrodes in nonaqueous media are often inevitable. Unfortunately, so far, little has been known about the extent to which the properties of the ISEs could be affected by the organic solvents. Herein, the feasibility for the applications of the polymeric membrane ISEs in nonaqueous media has been investigated. A polymeric membrane Ca-ISE is chosen as a model of potentiometric sensors. Four typical water miscible organic solvents (three protic solvents: ethanol, acetic acid, and methanol, and one aprotic dipolar solvent: acetonitrile) are used as the representative examples. Experiments show that the aprotic solvent acetonitrile has the strongest destructive ability towards the sensing performance of the ISE in terms of Nernstian slope and selectivity coefficient. Moreover, the effect on the sensing performance depends on the kind of the protic solvent, the immersion time and the polarity of the membrane plasticizer. We believe that the obtained results could promote further applications of the polymeric membrane ISEs in the organic solvent-containing samples, which could significantly extend the application scope of the ISEs.