Conductometric sensor for potassium ion profiling using lipophilic salt-incorporated non-toxic ion-selective membrane

Conductometric ion-selective electrodes (ISEs) offer a promising alternative to conventional potentiometric ISEs due to their suitability for miniaturization, real-time monitoring, and reduced calibration requirements. Here, a non-toxic potassium-selective ionophore, 2-dodecyl-2-methyl-1,3-propanediyl bis[N-[5′-nitro(benzo-15-crown-5)-4′-yl]carbamate] (K-III/BME-44), was incorporated into a polyvinyl chloride (PVC)-based ion-selective membrane (ISM), along with the lipophilic salt potassium tetrakis(4-chlorophenyl)borate (KTpClPB). The membrane was deposited onto gold interdigitated electrodes to facilitate impedance-based measurements. Sensor performance was evaluated, demonstrating that the sensitivity, selectivity, and dynamic range of the ISE can be modulated by adjusting the concentration of KTpClPB. The optimized K-III-based ISEs exhibited a threefold higher response compared to the commonly used, but toxic, valinomycin-based counterpart under equivalent conditions. Selectivity coefficients, determined using both the Separate Solution Method (SSM) and the Fixed Interference Method (FIM), confirmed excellent potassium selectivity comparable to established potentiometric ISEs. These results highlight the potential of K-III-based conductometric ISEs for safe and accurate potassium detection in complex bioanalytical environments.