Interpretation of selectivity coefficients of solid-state ion-selective electrodes by means of the diffusion-layer model.
On the basis of a diffusion-layer model the selectivity coefficients of solid-state electrodes have been interpreted. In the Nernst equation the concentration of the principal ion may be expressed in terms of the diffusion coefficients D(B), D(C) and the equilibrium constant K of the reaction AB + C right harpoon over left harpoon AC + B where AB represents the membrane material and C the interfering ion, in the form of an equation: [B](0)=KD (B)KD (B) + D (C)[B] + KD (C)KD (B) + D (C)[C] where the concentration with subscript "0" denotes the surface concentration directly influencing the electrode potential, and [B] and [C] are bulk concentrations of the species indicated. The differences between various literature data can be explained on the basis of this model.
Hulanicki
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Institute of Fundamental Problems in Chemistry, The University, Warsaw, Poland.
Lewenstam
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