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 dimension of similar to 10 mu m in diameter, are described. A CDUME was constructed by inserting a carbon fiber 7 mu m in diameter into a commercial Teflon capillary, which was followed by pulling the capillary by means of a microelectrode puller employing appropriate heating and timing, to produce a self-sealing thin Tenon film insulation coating. Then, the so-coated carbon fiber was cut to expose a fresh carbon fiber disk, The proposed one-stage preparation method is fast (similar to 5 min), very simple, and inexpensive and eliminates the need for separate embodying, insulation, and sealing steps. It results in CDUMEs exhibiting excellent electrochemical behavior. Scanning electron and optical microscopy, voltammetry, and amperometry were employed to characterize these electrodes. Cyclic voltammograms of ferricyanide in aqueous media and of ferrocene in acetonitrile media displayed low-noise, low-background, 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 voltammetry 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 obtained with a detection limit of 7.0 x 10(-7) mol/L. The proposed CDUMEs with flexible and nonfragile Tenon housing exhibit very low electrical noise and can be reproduced multiple times by simply recutting the tip.