Determination of Antioxidant Capacity by Using Xanthine Oxidase Bioreactor Coupled with Flow‐through H2O2 Amperometric Biosensor

Abstract

AbstractA new flow system for antioxidant capacity (AOC) estimation, consisting of a bioreactor, containing immobilized xanthine oxidase (XOD), coupled with a H2O2 amperometric biosensor, based on Os‐wired horseradish peroxidase, was developed. The H2O2, resulting from the enzymatic reaction between xanthine (XA) and XOD, was amperometrically monitored at −0.1 V vs. Ag/AgCl/KClsat, in order to avoid the electrochemical interferences. Two protocols were used to perform the AOC evaluation: “steady‐state”, when the antioxidant (AOX) was injected in the XA flow, and “transient state”, when XA and AOX were simultaneously injected in the carrier flow. The AOC of some commercial beverages were evaluated and compared with those obtained with 2,2‐diphenyl‐1‐picrylhydrazyl radical and Folin–Ciocalteu methods.