Three-phase electrochemistry with a cylindrical microelectrode

A new experimental approach is proposed to examine the ion transfer across the boundary of two immiscible liquids. A cylindrical platinum or gold microelectrode is immersed into the two-liquid system in such a way that a part of it is located in one liquid and the other part resides in the second liquid. The organic liquid contained either ferrocene or decamethylferrocene and no supporting electrolyte. The aqueous phase contained various inorganic salts. Well defined and reproducible linear-scan and square-wave voltammograms of oxidation of ferrocene and decamethylferrocene were obtained. The dependence of the formal potential derived from the square-wave voltammograms of decamethylferrocene vs. the standard potentials of transfer of anions present in the aqueous phase was perfectly linear. The developed method is more precise, since the three-phase boundary is better defined compared to placing a drop of organic liquid on the surface of a graphite electrode, and should be applicable to a larger set of organic liquids.