Potentiometric selectivity of ion-selective electrodes for alkaline-earth elements based on podands with phosphoryl terminal groups

Dependence of the analytical characteristics (detection limits, DLs) and potentiometric selectivity Kijpot) of the ion-selective electrodes (ISEs) based on phosphoryl-containing podands on the structures was investigated. It was demonstrated that the DL was determined by complex facilitated transfer energy. It was shown that the DLs of the majority of the ionophores weakly depend on the lipophilicity of the ionophores. Ionophore selectivity is determined by the difference of the facilitated transfer energies of both test and interfering ions and by the properties of the electrochemical system. Stability of complexes makes a major contribution to the energy accompanied with the transfer of the complex and is determined by the disposition of metaldonor atoms of ionophore bonds and by other properties of the electrochemical system, specifically, the dielectric permeability of the medium. Increasing the denticity by increasing the ethyleneglycol chain number leads to the transformation of CaBa to BaCa-selectivity. The introduction of the two-fold excess of the sodium tetraphenylborate (mol% to ionophore) in membrane composition results in increasing barium selectivity for alkali and alkaline-earth elements. An ISE for the determination of barium was prepared.