Ion transfer across a liquid membrane. General solution for the current-potential response of any voltammetric technique

Abstract

An explicit analytical equation applicable to the study of reversible ion transfer at systems with two liquid/liquid polarizable interfaces is presented. This expression is valid for any multipotential step technique, which are all very adequate for the determination of standard transfer potentials and transport parameters of ions. The expression of the I/E response for linear sweep voltammetry and cyclic voltammetry can also be deduced as a particular case of this equation. The general solution given here is formally similar to that obtained for the application of any multipotential step sequence to a system with a single polarizable interface, since the method followed here is based on the same premises.

Mechanism of Ion Transfer in Supported Liquid Membrane Systems: Electrochemical Control over Membrane Distribution

“…Molina et al derived a substantial theoretical body of work, supported with experiments, to describe voltammetry at membrane interfaces; however, only cases where fairly hydrophilic ions were present in one of the aqueous phases were considered, in contrast to the RB + case described above. 12,13,54 …”

Study of ion transfer through liquid membrane systems by Current Reversal Chronopotentiometric techniques

“…Two platinum counter electrodes work as a source and drain of current, while the potential difference across the system is measured with two Ag/ AgCl reference electrodes placed closed to the interfaces. The membrane measured potential is given by E ¼ E out À E inn þ IR, being E out the potential difference at the outer interface between the sample solution and the membrane and E inn that of the inner interface between the membrane and the inner solution (that is constant at the system of a single polarized interface) [10].…”

“…Both systems consist of an organic membrane that separates two aqueous solutions, but in the former, the polarization phenomena is only effective at one of the two liquid/liquid interfaces involved (the sample solution/membrane interface), while in the latter, both interfaces are polarized [3][4][5][6][7][8][9][10].…”

Use of voltammetry for in vitro equilibrium and transport studies of ionisable drugs

“…Other reports made significant contribution to the polarised membrane research, albeit not directly studying pharmaceutically relevant molecules [59][60][61][62][63]. Significant efforts have also been spent on development of an electrochemical theory to describe the observed current-potential dependence, both for systems with and without membrane electrolytes [64][65][66][67]. Furthermore, a number of research activities have focused on use of SLMs as ion-selective electrodes applied to drug molecules [68].…”