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The interaction between glucose oxidase (GOx) and phospholipid monolayers is studied at the 1,2-dichloroethane/water interface by electrochemical impedance spectroscopy. Electrochemical experiments show that the presence of GOx induces changes in the capacitance curves at both negative and positive potentials, which are successfully explained by a theoretical model based on the solution of the Poisson-Boltzmann equation. These changes are ascribed to a reduced partition coefficient of GOx and an increase of the permittivity of the lipid hydrocarbon domain. Our results show that the presence of lipid molecules enhances the adsorption of GOx molecules at the liquid/liquid interface. At low lipid concentrations, the adsorption of GOx is probably the first step preceding its penetration into the lipid monolayer. The experimental results indicate that GOx penetrates better and forms more stable monolayers for lipids with longer hydrophobic tails. At high GOx concentrations, the formation of multilayers is observed. The phenomenon described here is strongly dependent on 1) the GOx and lipid concentrations, 2) the nature of the lipid, and 3) the potential drop across the interface.

The coordination chemistry involved in the assisted transfer of RhIII by interfacial coordination with 2,5,8-trithia[9],(2,9)1,10-phenanthrolinophane (L) has been studied at the water/ 1,2-dichloroethane interface by cyclic voltammetry. The dependence of the half-wave transfer potential on the ligand and metal concentrations suggests the [Rh(L)Cl2] formulation for the complex cation involved in the assisted transfer. In contrast, from the reaction of L in refluxing MeCN/water

In this work, the analytical use of facilitated ion transfer of catecholamines by dibenzo-18-crown-6 was investigated at the water/1,6-dichlorohexane interface using electrochemical methods (cyclic and square wave voltammetry). The experimental conditions for the analytical determination of noradrenaline and dopamine were established and detection limits of 1.7 and 0.35 µM were obtained, respectively. The effect of excess ascorbic acid on the transfer and detection of the two catecholamines was investigated. The selectivity coefficients obtained for dopamine and noradrenaline in the presence of ascorbic acid were 3.5×10−4 and 2.5×10−3, respectively.

The transfer of a phenolsulfonephthalein dye (bromophenol blue, BPB) across the water/1, 2-dichloroethane (DCE) interface was studied by means of cyclic voltammetry, two-phase extraction techniques and in situ spectrophotometry. For the first time it was observed the transfer of two differently charged species originated from deprotonation of H2BPB. The values of the acidity constants were obtained (pK=3.1±0.2 and pK=pK 4.3±0.2) and an ionic partition diagram of BPB between water and DCE was constructed. The diagram is the basis for the proposed dye transfer mechanism which was validated using voltabsorptometric measurements. Physicochemical parameters were also obtained and relations between lipophilicity and structure accessed.