The research results facilitate the description of adenine adsorption on the mercury electrode with reference to the pH of the supporting electrolyte which was the acetate buffer with pH of 3, 4, 5 and 6. The thermodynamic analysis indicates that the curves of the differential capacity of the studied systems with adenine do not overlap with the curves for the supporting electrolyte – the acetate buffer. This indicates the occurrence of adsorption of the studied compound on the mercury electrode within the whole range of applied concentrations in the case of every tested pH value of the acetate buffer. Adsorption energy and interaction constants were determined using the Frumkin isotherm and the viral isotherm. It was demonstrated that a adenine molecule is adsorbed on the mercury electrode in a buffer with pH 4, 5 and 6 through the negative pole, whereas in a buffer with pH 3 through the positive pole. Physical adsorption was observed in the studied systems. This is indicated by the occurrence of a typical maximum on the curve of the relation the relative surface excess amounts and the potential of the electrode; crossed curves of the following relation surface charge of the electrode from its potential (surface charge of the electrode from its potential σ = f(E)) at one point and, thus, the possibility of determining electrical parameters characterizing maximum adsorption as well as the absence of linearity of the function free energy of adsorption as a function of electrode potential ∆G0 = f(E).