Influence of lipophilic anionic compounds on the selectivity of ion-selective electrodes based on podands with phosphoryl complexing groups

The dependence of the potentiometric selectivity of ion-selective electrodes (ISEs) based on phosphoryl-containing podands on concentration of the lipophilic compounds (sodium tetraphenylborate or potassium tetrakis-p-Cl-phenylborate) was investigated, It was demonstrated that the selectivity of the Ca- or/and Ba-selective electrodes over the alkali metals (AMs) and alkaline-earth metals (AEMs) increases with the lipophilic compound content. In case of AMs the changes of the selectivity is larger than for AEMs, It was shown that employment of the more lipophilic compound, namely, the potassium tetrakis-p-Cl-phenylborate, leads to the greater selectivity growth than for the sodium tetraphenylborate, A qualitative model which describes the potential-formation mechanism at the introduction of the lipophilic compounds in membrane composition was proposed. (C) 1999 Elsevier Science B.V. All rights reserved.