The electrochemistry of 2,2-diphenyl-1-picrylhydrazyl (DPPH) in acetonitrile was studied in presence of ascorbic acid (AAH 2 ) as model antioxidant. In the presence of AAH 2 , the intensities of the two characteristic systems of DPPH decreases and an intense oxidation peak at 1.07 V assigned to the oxidation of reduced DPPH was observed. The currents associated to these electrochemical processes showed excellent correlation with the amount of AAH 2 added and were used for determining its free radicals scavenger activity. Chronoamperometry was found more suitable for a real time monitoring of the chemical reaction between DPPH and an antioxidant, and thus to evaluate their efficiencies by determining the corresponding half-maximal inhibitory concentration (IC 50 ) values. Comparison of the reactivity of the antioxidants tested was possible by comparing the times necessary for the stabilization of the residual DPPH reduction currents. The method was subsequently applied to the evaluation of antioxidant properties of lemon and orange samples.[a] Dr.