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

Abstract

A polarization study carried out on a thin supported liquid membrane separating two aqueous compartments is presented. Transfer of both the ionized and uncharged form of an organic tracer dye, rhodamine B ([9-(2-carboxyphenyl)-6-diethylamino-3-xanthenylidene]-diethylammonium chloride), across supported liquid membranes composed of one of 1-octanol (octan-1-ol), 1,9-decadiene (deca-1,9-diene), 1,2-dichlorobenzene, or nitrophenyl octyl ether (1-(2-nitrophenoxy)octane) was studied using cyclic voltammetry and UV–vis absorption spectrophotometry. Concentration analysis indicates that the high membrane concentration of rhodamine B determines the ionic transfer observed via voltammetry, which is consistent with the low aqueous ionic concentration and large membrane/aqueous distribution of the molecule. The observed double-transfer voltammogram, although it has been largely neglected in previous literature, is a logical consequence of the presence of two liquid–liquid interfaces and is rationalized in terms of ion transfer across the two interfaces on either side of the membrane and supported by voltammograms obtained for a series of ions of varied lipophilicity. The bipolar nature of the voltammetric response offers an effective way of mass transport control via changing polarity of the applied voltage and finds immediate use in extraction, purification, and separation applications.

Paper-supported thin-layer ion transfer voltammetry for ion detection

“…1, with increasing applied potential, the oxidation of Ag results in the cation transfer from the sample to the inner solution of the electrode. Increasing the hydrophilicity of the ions results in an increasing potential to transfer ions across the membrane [31]. Therefore, the cation exchanger membrane with its higher selectivity in the Hofmeister series exhibits a high preference for TBA + over other ions in the sample.…”

Electrochemical Study on Quantitative Structure‐activity Relationship (QSAR) Analysis under Steady‐state Conditions

“…According to the law of mass conservation, the relation between the initial concentrations in W and O and the concentrations in W and O after the distribution equilibrium can be expressed as eqn. (22).…”

“…As for the ion transport between two aqueous phases across a liquid membrane, the author's group and Horvá th [ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 and Horvai reported the analytical method by considering the ion transfers at two W j O interfaces [13][14][15]. Several research groups have studied the permeation properties based on the analysis of the interfacial transfer and the membrane transport [16][17][18][19][20][21][22]. Nakamura and Osakai explained the plateau region observed for hydrophobic drugs based on the theoretical analysis of PAMPA [23].…”

Electroanalytical Opportunities Derived from Ion Transfer at Interfaces between Immiscible Electrolyte Solutions

“…[33b, 42] Recently, Dryfe et al [57] examined the effect of a bipolar ITIES in a supported liquid membrane (SLM)…”

“…Although some groups [58] around the world had already addressed the behaviour of membranes with two polarisable interfaces, the main trend with SLMs has been the investigation of only a single polarisable interface. In this work, [57] the transfer of analytes across the membrane was followed with a photosensitive probe (rhodamine) via UV-vis absorbance, so as to determine the ion distribution profiles in the SLMs. It also showed that both the membrane and aqueous phases can behave as donor/acceptor phases due to the reversibility of the system.…”