Generalized Diffusion Parameter: Main Factors of Influence and Application for Estimation of Selectivity Coefficients for Highly Selective Electrodes

The influence of membrane composition, ion nature, measuring time and stirring mode on the generalized diffusion parameter q was investigated. It was found that the main factors of influence are PVC to plasticizer ratio and measuring time, which obey rigid regularities and can be estimated. It makes possible to evaluate the role of the diffusion factor for other systems and measuring conditions using some averaged q value determined for a limited set of systems. It was shown that averaged q value allowed reliable estimating of low selectivity coefficients (down to 10−8) from strongly biased values determined by separate solution method.