Improvement of Lower Detection Limit of Ion-Selective Electrodes Based on PVC Membrane

Ion-selective electrodes (ISEs) based on polymeric membranes are characterized by small size, portability, low-energy consumption, and low cost, which are attractive features concerning practical applications. However, the lower detection limit is biased by the ion flux through PVC membrane, which limits the further development of ion-selective electrode. Therefore, the principles and attractive strategies to suppress such an ion flux to improve the lower detection limit of PVC membrane-based ion-selective electrodes are elaborated in this article. According to large amounts of data collected, the improvement of the detection limit via optimization of sensing membrane composition, electrode assembly and conditioning, electrode rotation, as well as current-polarized treatment, is quantitatively discussed. Furthermore, the modification regulations for expanding the lower detection limit are systematically summarized. The significant superiority and problems are analyzed. It is pointed out that we have to break the conventional PVC composition formulation via reducing the dosages of plasticizer and ion exchanger in order to largely depress the transmembrane ion flux. External-current application to the electrode is also an effective approach, among which, the best improvement for the lower detection limit can reach up to 5 orders of magnitude. This review reveals the future direction for developing the PVC membrane-based ion-selective electrodes with high performance.