Oxidation of ferrocene in acetonitrile resulted in films on Pt electrodes under voltammetric conditions. Films were more readily formed with tetrabutylammonium tetrafluoroborate as the electrolyte than with perchlorate salts. No films were detected when ferrocene was oxidized in aqueous 0.05 M cetyltrimethylammonium bromide (CTAB). Analysis of the films by FT-IR and Auger spectroscopy confirmed iron-containing oxidation products on Pt, presumably from chemical reactions of ferricinium ions. Oxidation of 50-100 mM ferrocene in acetonitrile on Pt yielded insoluble precipitates. Analyses by MS, FT-IR, and UV-visible (water extract), suggested a mixture of oligomeric material and a small fraction of ferricinium ions. Film formation had much less influence on voltammograms on 12.5-micron-radius Pt microdisks than on 0.5-mm-radius Pt. This is consistent with the smaller sensitivity of microelectrodes to chemical reactions following charge transfer. The smaller apparent heterogeneous rate constants (k zero') found for ferrocene on macroelectrodes than on microelectrodes could possibly be influenced by film formation on larger Pt electrodes. Correlations between macro- and microelectrode kinetic data suggest that macroelectrode k zero' values may be valid in a relative sense when ohmic drop is negligible. Bias in k zero's on conventional-sized electrodes should be small in solutions giving minimal film formation, such as micellar CTAB.

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Kinetics of electrochemical oxidations of ferrocene (Fc) and 2-and 5-(ferrocenylcarboxy)dodecyltrimethylammonium nitrates (2-Fc and 5-Fc, respectively) were studied to yield information about the electrode-fluid interface in a bicontinuous microemulsion. Apparent standard heterogeneous electrontransfer rate constants (k°') for Fc, 2-Fc, and 5-Fc at glassy carbon electrodes were similar in homogeneous acetonitrile, as found earlier in DMSO. In a bicontinuous microemulsion of n-tetradecane, water, pentanol, and cetyltrimethylammonium chloride (CTAC), electron-transfer rates for Fc, 2-Fc, and 5-Fc were an order of magnitude smaller than in acetonitrile. Ferrocene had ak°' twice as large as 2-Fc and 5-Fc in the CTAC microemulsion. Small differences in rates of 2-Fc and 5-Fc cannot be explained by a head down-tail up orientation at the time of electron transfer, as proposed to explain kinetics in micellar CTAB solutions. Results suggest the possibility of increased disorder and mobility in the electrode-fluid interface in the CTAC microemulsion compared to micellar CTAB solutions.

An undergraduate laboratory experiment has been developed in which the students extract and analyze the additives from plastic food wrap, Tygon tubing and plastic soda bottles that have been crushed in a bottle return machine. The modifiers are extracted from the plastics using methylene chloride and/or methanol as solvents and the extracts are analyzed by GC/MS. Identifications are carried out by a combination of automated computer and manual library searches and chromatographic retention indices.

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