This work reports the in situ cobalt(II) phthalocyanine (CoPc) synthesis on a SiO2/SnO2(SiSn) matrix surface. SiSn was previously obtained by the sol-gel method as a powder xerogel with SnO2 compositions (in wt%) of 3.0, 8.6 and 12.3. The new materials synthesized (SiSn/CoPc) were tested as electrode materials in the electrocatalytic oxidation of oxalic acid. The material SiSn/CoPc containing 12.3 wt% was chemical and morphologically characterized by U-V-vis, FTIR, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The UV-vis and FTIR spectrums confirm the effective immobilization of CoPc on SiSn by an in situ synthesis. The electrochemical responses and corresponding electrocatalytic activity of the electrode were evaluated by cyclic voltammetry and chronoamperometry. The adsorbed phthalocyanine electrocatalyzed the oxalic acid oxidation at 0.77 V (versus SCE). The anodic peak current intensities, plotted against oxalic acid concentrations between 5 x 10(-5) and I X 10(-3) mol L-1 were linear, with a correlation coefficient (r(2) = 0.996) and a detection limit of 3 x 10(-5) mol L-1. (C) 2007 Elsevier B.V. All rights reserved.