Mesoporous structured silica modified with niobium oxide and cobalt hematoporphyrin applied to the simultaneous electrochemical evaluation of oxalic and uric acids

Mesoporous SBA-15-type silica, with cylindrical pores hexagonally ordered, was obtained and modified with niobium oxide in a highly dispersed way. Subsequently, a further modification with cobalt hematoporphyrin was performed. The ordered pore structure of the SBA-15 was preserved after successive modifications, maintaining its textural properties. The material was used to modify a carbon paste electrode that was successfully applied to the individual and simultaneous detection of both oxalic acid and uric acid, by using cyclic voltammetry and differential pulse voltammetry. For individual evaluation, the obtained detection limits for oxalic acid and uric acid were 9.94 and 0.17 μmol∙L−1, respectively. However, for the simultaneous evaluation of both analytes, the detection limits were 2.83 and 0.14 μmol∙L−1, for oxalic acid and uric acid, respectively.