On the possibilities of potentiometric analysis in presence of small concentrations of highly interfering foreign ions: Ways for reducing the interference

Abstract The influence of a series of easily controlled factors on the results of direct potentiometric determination of target ions in presence of small concentrations of highly interfering foreign ions is investigated using digital simulation in the framework of the recently proposed interface equilibria-triggered dynamic diffusion model. It was shown that targeted control of such factors of influence as the dilution of the sample solution, the rate of stirring, the concentration of the ion exchanger and the ratio of polymer to plasticizer in the membrane, as well as the measuring time, allows reducing the influence of foreign ions for several decimal orders. The results of the calculations are in good agreement with experimental data that makes it possible to reveal, on the basis of simulation results, the key factors of influence on the practical selectivity of the electrode and to propose rational ways for optimizing the membrane composition and the experimental conditions in order to reduce the influence of highly lipophilic foreign ions on the results of direct potentiometric determination.