The oxidations of NADH, epinephrine, and norepinephrine are studied using carbon nanotube and graphite powder-modified basal plane pyrolytic graphite electrodes. Immobilization is achieved in two ways: first, via abrasive attachment of multiwall carbon nanotubes or graphite powder by gently rubbing the electrode surface on a fine quality paper supporting the desired material; second, via "film" modification from dispersing either graphite powder or nanotubes in acetonitrile and pipeting a small volume onto the electrode surface and allowing the solvent to volatilize. While electrocatalytic behavior of both types of nanotube-modified electrodes is shown, with enhanced currents and reduced peak-to-peak separations in the voltammetry in comparison with naked basal plane pyrolytic graphite, similar catalytic behavior is also seen at the graphite powder-modified electrodes. Caution is, therefore, suggested in assigning unique catalytic properties to carbon nanotubes.

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The first example of using an edge plane pyrolytic graphite electrode in electroanalysis is reported as the determination of homocysteine, N-acetylcysteine, cysteine and glutathione is studied. The response of the electrode in the direct oxidation of thiol moieties is explored and found to be electrocatalytic producing a reduction in the overpotential while having enhanced signal-to-noise characteristics compared to glassy carbon and basal plane pyrolytic graphite electrodes. The effectiveness of the methodology is examined in the determination of cysteine species in a growth tissue media that contains a high number of common biological interferences. The advantageous properties of this electrode for thiol determination lie in its excellent catalytic activity, sensitivity and simplicity.

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The basis of the electrocatalytic nature of multi-wall carbon nanotubes is suggested to reside in electron transfer from the ends of nanotubes, which structurally resemble the behaviour of edge plane (as opposed to basal plane) graphite, and is demonstrated via the comparison of the electrochemical oxidation of epinephrine and the electrochemical reduction of ferricyanide at nanotube-modified electrodes using different types of graphite electrodes and with C(60)-modified electrodes.