A modified carbon paste electrode was prepared by incorporating TiO2 nanoparticles and ferrocene carboxylic acid (FCCa) in carbon paste matrix. Electrochemical impedance spectroscopy (EIS) indicates that the TiO2nanoparticles efficiently decreased the charge transfer resistance value of electrode and increased the porous microcrystalline structure of it to improve the electron transfer kinetic between FCCa and electrode. FCCa acted as a mediator between the analyte and electrode surface. The electrocatalytic oxidation of glutathione (GSH) and tryptophan (Trp) is individually and simultaneously investigated at the surface of FCCa–TiO2 modified electrode using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electrode is able to completely resolve the voltammetric response of GSH and Trp from potentially interfering species, e.g. ascorbic acid (AA) and tyrosine (Tyr), respectively. The linear range of the analytical plot remains constant in binary mixture solutions of GSH and Trp. High sensitivity and selectivity together with very low detection limit of the electrode response make it very suitable for simultaneous and individual determination of trace amounts of GSH and Trp in pharmaceutical and clinical preparations
