The perfluorosulfonated ionomer Nafion shows potential utility as a polymer film to enhance the electrochemical detection of [ReI(DMPE)3]+, where DMPE = 1,2-bis-(dimethylphosphino)ethane. [ReI(DMPE)3]+, a nonradioactive radiopharmaceutical analog for heart imaging, partitions strongly into Nafion films on glassy carbon. Well-defined, chemically reversible cyclic voltammograms are obtained for the [ReI(DMPE)3]+/[ReII(DMPE)3]2+ couple with Eo' shifted positively by 60 mV relative to its value on bare glassy carbon. [ReI(DMPE)3]+ partitions into Nafion more strongly than the oxidized form, [ReII-(DMPE)3]2+. The detection limit for [ReI(DMPE)3]+ by cyclic voltammetry was improved by 2-3 orders of magnitude by the Nafion film. Differential pulse voltammetry for oxidation of [ReI(DMPE)3]+ at the Nafion-modified electrode has a detection limit of 2.5 x 10(-9) M compared to 1.0 x 10(-7) M at the bare electrode. A preconcentration factor of 1 x 10(6) for partitioning of [ReI(DMPE)3]+ from 0.05 M NaCl into Nafion on a glassy carbon electrode was measured.

Cyclic voltammetry may be added to the limited repertoire of methods that may be used to examine solid/solution interphases for nonconductive solids, and to select nonconductive solids as heterogeneous electrocatalysts. Hexacyanoferrate(III) was used as an electroactive probe to determine the availability of Zn2+ and Al3+ ions at the surface of a layered double hydroxide (LDH, or hydrotalcite‐like clay, anion exchanging clay, or mixed metal hydroxide). The solid LDH, Znx2+Aly3+false(Cl−)zfalse(OH−)2x+3y−z·mH2O was applied to the surface of a glassy carbon electrode via its suspension in polystyrene/methylene chloride solution. Cyclic voltammetric experiments showed formation of a Prussian blue‐like film on the surface of the LDH, showing that the zinc and aluminum sites were available to form complexes with species in solution. No film formed on the Mg/Al/Cl analog, or on normalAgCl , SnO2 , or Al2O3 . Electro‐oxidation of phenol was catalyzed by the Mg/ Al/Cl LDH, but not by the Zn/Al/Cl compound. These results were used to assign effective pH values of >11.2 and 8.3, respectively, for the surfaces of these solids. Electrochemical results are compared with those obtained using x‐ray photoelectron spectroscopy (XPS).