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Abstract: Electrochemical behaviour of glutathione (GSH) at Au-nanoparticles based sensors (AuNP-sensors) was explored using cyclic voltammetry (CV). The obtained results reveal more catalytic activity of the AuNP-sensor toward the oxidation of GSH than gold film (Au-GE) modified graphite electrode due to increase in number of Au atoms at the surface of Au nanoparticles deposited at the graphite electrode. Electrocatalytic oxidation of GSH occurs at +0.05 V (vs. silver chloride ref. electrode) in 0.1 M NaOH and is revealed from CV as an “inverse” current peak in the cathodic direction of potential scan. Concentration of GSH in the interval 2–14 pM linearly influences on the peak height at AuNP-sensor with detectability threshold of 0.7 pM. The sequence of electrode reactions has been suggested which includes oxidation of Au nanoparticles when potentials scanned towards positive direction up to 0.8 V and consequent GSH electrocatalytic oxidation by Au(I)-oxide during the backward potential scan represented as the “inverse” peak. The proposed analytical method of GSH determination is simple, rapid and sensitive.