The role silica pore structure plays in the performance of modified carbon paste electrodes

Four silica materials was prepared by using different synthesis procedures, with the goal of obtaining matrices with different designed textures, microporous, mesoporous, and ordered pore structured materials, as MCM-41 and SBA-15. These silica materials were used to prepare bare carbon paste electrode, without addition of other components, as nanostructured or electroactive species. In this way, it was possible to study the influence of the textural characteristics, such as surface area, pore volume, pore size, and pore shape on the electrode performance, in a detailed and individual form. The electrodes were studied by using [Fe(CN) 6 ] 3−/4− and sulfamethoxazole as probes, in diffusional processes, employing cyclic voltammetry and differential pulse voltammetry. It was observed that surface area and pore volume contribute expressively to the electroactive area. The worst results were attained for microporous materials (0.34 cm 2 ), while the higher electroactive area values were obtained for materials with ordered pore structure, 2.01 cm 2 for MCM-41 and 2.58 cm 2 for SBA-15, by using [Fe(CN) 6 ] 3−/4− as probe. Regarding sulfamethoxazole as probe, the MCM-41 modified carbon paste electrode presented the best performance. The obtained sensitivity was 24.34 nA L μmol −1 and the detection limit found was 3.10 μmol L −1 . These results are satisfactory considering the electrodes are constituted just by bare silica, easy to prepare, without addition of other components.