Hybrid silica films containing cation‐exchange polyelectrolytes were designed and used to modify a glassy carbon electrode (GCE) for voltammetric determination of purine bases. Hybrid silica‐polyelectrolyte films synthesised in the presence of adenine as structure directed component have demonstrated enhanced sorption capacity to purine base. The anodic peaks of adenine and guanine at a hybrid film‐modified GCE were observed at +1.55 and +1.1 V, respectively, in phosphate buffer solution at pH 3.5. Oxidation currents of adenine and guanine were proportional to their concentration in the range of 0.02–0.50 mM, with a detection limit of 0.015 mM. The developed method was used to determine adenine in adenosine triphosphate and purine bases in hydrolyzed solutions of DNA and demonstrated good metrological characteristics.