Effects of ion transport on the potential response of ionophore-based membrane electrodes: A theoretical approach

A theoretical description of the steady-state potential response of ionopho re-based ion-selective electrodes is presented that, so far, is the most ge neral formalism available. The treatment considers membrane systems with an y number of ionophores, differently charged cations, anions, and fixed or s tationary ionic sites. The theory accounts for thermodynamically controlled selectivity characteristics, as well as for various diffusion-induced effe cts resulting from transmembrane ion fluxes at zero current. The phenomena discussed in detail include apparent super- and sub-Nernstian responses and detection limits. An extension of the treatment for time-dependent phenome na is also given. The present approach can be applied for optimizing the se lectivity coefficients and improving the detection limits of ionophore-base d ion-selective electrodes.