Electrochemical detection of natural antioxidants: principles and protocols.

An overview is provided of the use of cyclic voltammetry and electrochemical detectors for HPLC to characterize antioxidants that are active as reducing agents at inert electrodes. Results are presented for cyclic voltammetry at a glassy carbon electrode in 50% methanol, 50% 0.1 M HClO4, a solution typically used in HPLC separations of natural antioxidants. The relative reducing strength of each antioxidant is estimated by the formal potential, and information is also obtained regarding the reversibility of the oxidation of the antioxidants, and the extent to which the carbon electrode is contaminated by the products of oxidation. Cyclic voltammetry of complex mixtures such as blood serum and wine produces a measure of the total antioxidant status due to antioxidants with a low oxidation potential. The results of cyclic voltammetry studies are relevant to interpreting the performance of carbon electrodes in electrochemical detectors for HPLC.