PERMEATION OF SOLUTES THROUGH AN ELECTROPOLYMERIZED ULTRATHIN POLY-O-PHENYLENEDIAMINE FILM USED AS AN ENZYME-ENTRAPPING MEMBRANE

Permeation of electroactive organic probes through an electroinactive and passivating poly-o-phenylenediamine (PPD) film electropolymerized on Pt and glassy carbon (GC) electrodes has been investigated by cyclic and rotating disk electrode (RDE) voltammetry. The access of solutes to the metal-polymer interface appears mainly governed by specific chemical interactions, influencing partition, and diffusion phenomena, rather than by exclusion effects based on molecular size or charge. Potential cycling of the film induces fine modifications in the chemical/physical structure of the polymer, as evidenced by electron spectroscopy for chemical analysis (ESCA) measurements and by an enhanced permeation of certain solutes. The membrane is, however, stable in the pH and potential range usually employed in its application, that is, as an enzyme-entrapping membrane in amperometric biosensors; because of membrane permselectivity, the electrochemical response of the most common electroactive interferents is deeply depressed.