POLY(TETRAFLUOROETHYLENE) FILM HOUSING OF CARBON-FIBERS USING CAPILLARY-PULL TECHNOLOGY FOR ONE-STAGE FABRICATION OF CARBON DISK ULTRAMICROELECTRODES AND THEIR CHARACTERIZATION

Fabrication and characterization of carbon disk ultramicroelectrodes ( CDUMEs), embodied in a pulled Teflon capillary, with overall tip dimen sion of similar to 10 mu m in diameter, are described. A CDUME was con structed by inserting a carbon fiber 7 mu m in diameter into a commerc ial Teflon capillary, which was followed by pulling the capillary by m eans of a microelectrode puller employing appropriate heating and timi ng, to produce a self-sealing thin Tenon film insulation coating. Then , the so-coated carbon fiber was cut to expose a fresh carbon fiber di sk, The proposed one-stage preparation method is fast (similar to 5 mi n), very simple, and inexpensive and eliminates the need for separate embodying, insulation, and sealing steps. It results in CDUMEs exhibit ing excellent electrochemical behavior. Scanning electron and optical microscopy, voltammetry, and amperometry were employed to characterize these electrodes. Cyclic voltammograms of ferricyanide in aqueous med ia and of ferrocene in acetonitrile media displayed low-noise, low-bac kground, sigmoidal responses with virtually no current hysteresis. To check the analytical applicability of these electrodes, a testing with adrenaline was performed by applying the differential pulse voltammet ry mode. A linear calibration over the concentration range from 2.5 x 10(-6) to 5.0 x 10(-4) mol/L in pH 7.2 phosphate buffer solution was o btained with a detection limit of 7.0 x 10(-7) mol/L. The proposed CDU MEs with flexible and nonfragile Tenon housing exhibit very low electr ical noise and can be reproduced multiple times by simply recutting th e tip.