Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The electrocatalytic activity of a supramolecular complex based on cobalt(II) phthalocyanine tetrasulfonate and iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin adsorbed on multi-walled carbon nanotubes for the oxidation of L-glutathione (GSH) was investigated at pH 7.4. Scanning electron microscopy and energy dispersive X-ray spectrometry were used to characterize the morphologies and composition of the materials. The modified electrode displayed efficient electrocatalytic activity in terms of oxidation of GSH at an oxidation potential of 0 V (versus Ag/AgCl). Cyclic voltammetry and amperometry indicated that the oxidation involves 2-electrons, with a heterogeneous rate constant of 4.9 x 10(5) mol(-1) L s(-1). The response is linear from 2 to 210 mu mol L(-1), the sensitivity is 1570 mu A L mmol(-1), the detection limit is 0.03 mu mol L(-1), and the relative standard deviation of 110 mu mol L(-1) GSH was 2.6% (n=10). The modified electrode was applied to the determination of GSH in erythrocytes and the results were in agreement with those obtained by a method reported in the literature.17141671169178Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)