The voltammetric behaviour of solid 2,2-diphenyl-1-picrylhydrazyl (DPPH) microparticles

The electrochemical behaviour of 2,2-diphenyl-1-picrylhydrazyl (DPPH) micro particles, attached to a graphite electrode and adjacent to an aqueous elec trolyte solution, has been studied by cyclic voltammetry. DPPH exhibits one reversible redox couple with a formal potential of 0.340 V versus Ag\AgCl (pH=7.0). At more positive potentials, a redox couple appears with a formal potential E-f=0.733 V versus Ag\AgCl. The oxidation at this potential is f ollowed by an irreversible chemical reaction generating a product which giv es a redox couple with a formal potential at 0.177 V versus Ag\AgCl. The re duction process of this couple is followed by a slow chemical reaction in t he course of which DPPH is reformed. (C) 1999 Elsevier Science S.A. All rig hts reserved.