Construction and characterization of carbon paste ultra-microelectrodes

The construction and characterization of carbon paste ultra-microelectrodes is reported. Besides a disc-shaped electrode, a carbon paste band electrod e is studied. It was found that for both electrode configurations steady-st ate currents were obtained but that with the type of electrode material use d for the band electrode, the upper limit of ultra-microelectrode dimension s, which could be used was 100-150 mum. Smaller dimensions for the band ele ctrodes resulted in a high resistance due to the limited conductivity of th e carbon paste, when using the optimal paste composition. With cyclic volta mmetry, the oxidation of [Fe(CN)(6)](4-) was studied at individual construc ted electrodes and at ensembles of individual electrodes. Detection limits of less than 10(-6) mol l(-1) were obtained. Using the data of the same cur ves it was possible to test if the electrodes have errors and about 20% of the constructed electrodes did not pass this test. Finally it was found tha t these electrodes show good stability. (C) 2001 Published by Elsevier Scie nce BN.