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The development of ion extraction methods under electrochemical control via electrochemistry at the interface between two immiscible electrolyte solutions is discussed. A hydrodynamic flow injection system was used for the potentiostatic extraction of non-redox-active species from a flowing aqueous phase into a stationary organogel phase. The ions tetraethylammonium, 4-octylbenzenesulfonate (4-[OBSA.sup.-]), andp-toluenesulfonate ([p-TSA.sup.-])were studied as model analytes. The extraction study comprised examination of the influence of extraction potentials, aqueous-phase flow rate, and target species concentration. The extraction process can be monitored in situ by means of the ion-transfer current, which has opposing signs for anions and cations. Hydrodynamic voltammograms were obtained from these experiments. The selective extraction of 4-[OBSA.sup.-], from its mixture with p-TSA-, as well as coextraction of both anions is shown. The results demonstrate the utility of electrochemical modulation for the controlled extraction of ions from an aqueous phase into an organogel electrolyte phase. This offers potential benefits for various analytical processes including sample preparation and cleanup.

The ready extension of the polarization window at the liquid/liquid interface can be achieved by modifying the interface with zeolite membranes. Use of the silicate membrane is reported which leads to the size exclusion of the ions employed as organic electrolyte and this approach can be used to allow the measurement of transfer potentials for extremely hydrophilic ions.

A hydrodynamic system based on the channel flow cell for voltammetric detection of ions at the liquid/liquid interface is reported. The current response for tetraethy-lammonium ion transfer across a membrane-supported liquid/liquid interface is shown to be consistent with existing theory for both the flow rate and voltage scan rate dependence of such processes, with no calibration factors or other adjustable parameters required. The analytical utility of such a device is discussed with specific regard to in situ measurements in flow systems.

The in situ measurement of EPR spectra of radical ions generated at the polarized liquid/liquid interface is described in relation to the 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrachloro-p-benzoquinone (TCBQ), and 2,3,5,6-tetrafluoro-p-benzoquinone (TFBQ) radical anions and the tetrathiafulvalene (TTF) radical cation. TCNQ and TTF were chosen as model compounds with which to quantify the performance of a novel liquid/liquid electrochemical EPR cell. The anion radical of TCNQ and the cation radical of TTF in 1,2-dichloroethane (DCE) were produced at the water interface by electron transfer from/to the aqueous-phase ferricyanide/ferrocyanide redox couple by applying a potential difference between the two phases with a four-electrode potentiostat. The EPR signal intensity (at constant magnetic field) of the resultant organic radicals was monitored during potential step experiments which indicated that the EPR data could be modeled in terms of diffusional transport. TCBQ and TFBQ were chosen as compounds to model the electron transfer behavior of biologically important quinones at the oil/water interface. The EPR and voltammetric data obtained from TCBQ/[TCBQ.sup.-[center dot]] and TFBQ/[TFBQ.sup.-[center dot]] indicated unambiguously that the two semiquinones are stable at the DCE/water interface and do not undergo immediate protonation.

The potential-controlled electron-transfer reaction between cyrochrome c and 1, 1'-dimethylferrocene at a liquid-liquid interface is reported. In this approach to protein electrochemistry, the electron transfer process is apparently transport controlled, rather than adsorption limited.

The growth and characterization of metallic nano-particles is studied by using different methods such as solution phase methods and electrochemical methods. Various aspects of these methods are combined in a study to induce the electroless deposition of palladium at the liquid-to-liquid (L/L) interface, with and without the presences of a membrane template.