Ion-Transfer Polarographic Study on the Lithium Ion Selectivity against Sodium Ion of Bis(8-quinolyloxy)propane Derivatives and Dibenzyl-14-crown-4 at Aqueous/Nitrobenzene Solution Interface

Abstract

Lithium and sodium ion transfers from water (w) to nitrobenzene (NB) phase containing Li⁺-selective neutral carriers (L), three bis(8-quinolyloxy)propane derivatives and dibenzyl-14-crown-4 (DBzl4C4), were studied by ion-transfer polarograph at 25°C. The logarithmic values of potentiometric selectivity coefficients were obtained by the relation $\log k_{\text{Lina}}^{\text{pot}} = (F/2.3RT)(\Delta \phi _{\text{Li}/\text{LiL}}^{ \circ '} - \Delta \phi _{\text{Na}/\text{NaL}}^{ \circ '})$ denotes the formal potential of the process ${\text{M}^ + }(\text{w - phase}) + \text{L}(\text{NB - phase}) \rightleftharpoons \text{M}{\text{L}^ + }(\text{NB - phase})$. They were −2.1 for DBzl4C4 and −1.₆-−1_.2 for bis(8-quinolyloxy)propane derivatives. The stability constants (mol⁻¹ dm³) of the 1:1 complexes for Li⁺ and Na⁺ in the NB-phase were also obtained from the metal ion-concentration dependence of the half-wave potentials. The Li⁺ selectivity of each carrier L against Na⁺ was discussed in terms of the values of $\Delta \phi _{\text{Li}/\text{LiL}}^{ \circ '} - \Delta \phi _{\text{Na}/\text{NaL}}^{ \circ '}$.