Permselective Behaviour at Overoxidised Poly[1-(2-carboxyethyl)pyrrole] Films: Dopamine Versus Ascorbate

Electropolymerised films of poly[1-(2-carboxyethyl)- pyrrole] were amenable to simple overoxidation, destroying the films’ electronic conductivity. The films so produced exhibited cation permselectivity in pH 7 buffer, allowing selectivity for dopamine detection in the presence of excess ascorbate: these compounds are a cation and an anion, respectively, at the pH studied. In addition, permselectivity was demonstrated by the inorganic complexes hexaminoruthenium(III), which was detectable at the overoxidised poly[1-(2-carboxyethyl)pyrrole] film, and hexacyanoferrate(III), whose electrochemistry was greatly inhibited at such films. The film has a carboxylate group in neutral solutions and so displays repulsion of anions and uptake of cations. Such films are easily deposited, allowing simple control of spatial location and film thickness and should be of use in sensor devices and flowing detectors, where additional selectivity besides that provided by the applied potential is necessary.