Electrocatalysis of reduced L-glutathione oxidation by iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeT4MPyP) adsorbed on multi-walled carbon nanotubes

The development of a highly sensitive voltammetric sensor for reduced L-glutathione (GSH) using a basal plane pyrolytic graphite (BPPG) electrode modified with iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeT4MPyP) adsorbed on multi-walled carbon nanotubes (MWCNT) is described. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to verify the morphologies and composition of the MWCNT after modification with the FeT4MPYP complex. The modified electrode showed very efficient electrocatalytic activity for L-glutathione oxidation, substantially decreasing the oxidation peak to -0.025 V vs Ag/AgCl. A linear response range from 5 mu mol L-1 to 5 mmol L-1 was obtained with a sensitivity of 703.41 mu A L mmol(-1). The detection limit for GSH determination was 0.5 mu mol L-1 and the relative standard deviation (R.S.D.) for 10 determinations of 250 mu mol L-1 GSH was 1.4%. The modified electrode was applied for GSH determination in erythrocyte samples and the results were in agreement to those obtained by a comparative method described in the literature. (C) 2008 Elsevier B.V. All rights reserved.