| A liquid/liquid interface has been considered as a simplest model for biological membranes and studies of ion transfer across this kind of interface is one of the hot topics in electrochemistry and electroanalytical chemistry at present. The ion transfer across the liquid/liquid interface can be applied in both environmental analysis and environmental toxicology assessment, where studies on kinetics and thermodynamics of ion transfer is fundamental for these applications mentioned above.A novel methodology of Fourier transformed/inverse Fourier transformed square-wave voltammetry (FT/IFT-SWV), initially developed by Bond and coworkers just since the beginning of this century, can be used to study the mechanism of electrode process. As FT/IFT-SWV has the power to resolve the electrode process in both frequency domain and time domain simultaneously, making it possible for simultaneous studies of kinetics and thermodynamics of ion transfer. The thin-film modified and edge plane pyrolytic graphite (EPPG) three-phase electrodes possess numerous merits of simplicity, practicality, being used in conventional three-electrode arrangement, popularity and mild environmental impact etc., hence they have been extensively used in studies of ion transfer across the liquid/liquid interface. In this paper FT/IFT-SWV was combined with thin-film modified and EPPG three-phase electrodes to study ion transfer across the liquid/liquid interface for the first time and the main results obtained were as follows:1. A novel method of FT-SWV in combination with thin-film modified electrode was employed to investigate the kinetics of anion transfer across the liquid/liquid interface using a conventional three-electrode arrangement. Other than traditional SWV in which currents are sampled only at the end of each pulse, FT-SWV continuously collects the current response and then transforms it into frequency domain. Even harmonic frequencies, which are derived from the faradaic current response, will emerge in the power spectrum. The profile of the even harmonic power spectrum is parabolic and shows a maximum at a certain frequency. The maximum and the corresponding frequency are equivalent to the well-known"quasireversible maximum"and"critical frequency"(fmax) in traditional SWV, respectively. The rate constant and ion transfer coefficientαcan be estimated by the obtained fmax. Compared with traditional SWV, FT-SWV is much simpler and faster in ion transfer kinetics estimation.2. The principle of EPPG three-phase electrode was investigated by cyclic voltammetry, and the obtained thermodynamic data of anions transfer across the water/nitrobenzene interface are more ideal, compared with those from published literature. The transfer of chromium (Ⅵ) ion across the water/nitrobenzene interface was observed for the first time and the thermodynamics of its transfer was determined. At the same time, SWV and FT-SWV associated with"quasireversible maximum"were comparatively used to study the kinetics of chromium (Ⅵ) transfer across the water/nitrobenzene interface.3. A systematical study of ion transfer across liquid/liquid interface was carried out by FT/IFT-SWV combined with EPPG three-phase electrode: on the one hand, testifying this method has the power to study kinetics and thermodynamics of ion transfer simultaneously; on the other hand, studying the effects of different kinds of ions and a kind of ion at different concentrations on kinetics and thermodynamics, besides, studying the effect of amplitude (ΔE) on"quasireversible maximum". The investigation mentioned above was aimed to optimize the conditions employed during the studies of mechanism of ion transfer across liquid/liquid interface and explore the potential of this method in quantitative analysis in the future, since investigation on mechanism as well as quantitative analysis are both beneficial for the advancement of environmental analysis and environmental toxicology assessment while the environment is deteriorating increasingly.
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