carbon fibers are used to construct microelectrodes with radii on the order of several microns. square wave voltammetry is employed to assess fabrication quality and to determine effective radii of properly constructed microelectrodes. the water-soluble polymer poly(n-vinyl pyrrolidone) is immobilized on microelectrode surfaces by gamma irradiation. the mechanism of immobilization is demonstrated to be polymerization rather than cross-linking by nuclear magnetic resonance spectroscopy or irradiated films. the utility of such films as electrode coatings for the detection of catechol compounds in the presence of the electroactive interferent ascorbic acid is demonstrated. examples of voltammograms for the positively charged catechol dopamine and the negatively-charged catechol dihydroxyphenylacetic acid, each in the presence of ascorbate at a concentration an order of magnitude higher, are presented. the oxidative depletion of ascorbate in such films is shown to further enhance the ability of such electrodes to detect catechol species in the presence of ascorbate. (author abstract) 34 refs