Achieving High Potential Stability of Solid-Contact Ion-Selective Electrodes: The Role of Solution with the Primary Ion Preconditioning of the Membrane Cocktail

Solid-contact ion-selective electrodes often struggle with potential stability during and between measurements. The potential drift significantly limits the reliability of the signal readout of ion-selective electrodes (ISEs), thereby limiting their practical applications. In this work, preadding a solution with the primary ion into the ion-selective membrane cocktail before drop-casting the ISEs was used to investigate the nature of ISEs' potential stability. It was found that preadding a solution with the primary ion into the ion-selective membrane cocktail not only facilitated a faster conditioning process but also contributed significantly to the membrane matrix. This led the ISEs to achieve low potential drifts (0.06 ± 0.03 mV/h) for around 15 days, surpassing the potential stability of any ISEs prepared by conventional means (0.21 ± 0.05 mV/h). Also, water infiltration into the ion-selective membrane and ion exchange are not the only key factors affecting the potential stability of ISEs during the conditioning process. For example, structural changes of the membrane matrix can influence the potential stability of ISEs. The newly studied preadding solution with the primary ion into the ion-selective membrane cocktail affects the membrane structure, which translates into achieving a stable potentiometric readout with solid-contact ISEs.