Changes in the microstructure of oil-in-water microemulsions were identified electrochemically by using ferrocene derivatives, methyl viologen, and ferricyanide as the electroactive probes. Microdroplets as well as the bicontinuous microstructure were detected. This was accomplished by determining diffusion coefficients of the probes. Use of probes of different hydrophobicity/hydrophilicity and charge made it possible to investigate different microenvironments of microemulsions including oil, water, and surfactant/cosurfactant interface. Electrochemical reversibility of the probes was affected by the structure and appeared to reflect the ease of mobility across interphases. Reaction potential (E1/2) of the probes depended on the composition of the microemulsion.

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30) ooeddel, D. V.; Heyneker, H. L.; Hozuml, T.; Arentzen, R.; Itakura. K.; Yansura. D. 0.; Ross, M. J.; Miozzari, G.; Crea, R.; Seeburg, P. H.Effect of the method of electrode treatment and the electrode material on the behavlor of the adsorbing small blologlcal molecule 2,6-dlamino-8-purinoi was evaluated. Electrochem lcal oxldatlon, polishlng, and laser activation were the methods of treatment that were compared and glassy carbon and rough pyrolytic graphite were the electrode materials. The results Indicate that effects such as chemlstry of the surface rather than microscopic surface area may determlne the b e havior of this adsorbing molecule.The chemistry and structure of graphite surfaces play a key role in heterogeneous electron transfer (I). Active surfaces, Le., surfaces at which kinetics of electron transfer are effec-tively catalyzed, can be produced by different methods. Improved electrochemical behavior is observed for compounds and at surfaces that are very different. This indicates that different mechanisms may be responsible for the effective catalysis (2). It has been suggested that a decrease in hydrophobicity of activated surfaces (2) may be the major factor in the observed catalytic behavior. It has also been proposed that activation follows desorption of impurities from the electrode surface (3, 4 ) .As a result of activation of glassy carbon electrodes by electrochemical treatment (5,6), polishing with alumina (3) and laser activation (4), background capacitance can increase. Increase in background capacitance has been related to an increase in adsorption (7). For example, when alumina-polished and heat-treated glassy carbon electrodes were com-

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