The reactivity of guanine, adenine and hypoxanthine on electrodes made with different materials is discussed. The rough pyrolytic graphite electrode (RPGE) was selected for the electrochem. study. The experiment data indicate that the electrode process is controlled by adsorption and the probes, guanine, adenine and hypoxanthine as mono-mol. layer are adsorbed toward the electrode surface of RPGE in a perpendicular orientation with the H group at C(2)-NH2 position for guanine, C(6)-NH2 position for adenine and N(1)-H position for hypoxanthine. Adsorbed mols. have a repulsive interaction at either surface. The equilibrium constants of adsorption for guanine, adenine and hypoxanthine are about 3.34 x 105, 4.38 x 105 and 4.13 x 105 resp., and the energies of adsorption at RPGE are about 31.5, 32.1, and 32.0 kJ/mol resp., which indicate that guanine, adenine and hypoxanthine all have a moderate to strong phys. adsorption on RPGE.

Key words: GUANINE, ELECTROCHEMICAL ANALYSIS, GRAPHITE, ADENINE, INTERACTIONS, ELECTRODE REACTION, SURFACES ADSORPTION, HYPOXANTHINE, SELECTIVE PARAFFIN OXIDATION, FUEL CELL