Evaluation of antioxidant capacity by triiodide methods

Abstract

Different methods have been developed for measuring the total antioxidant capacity. This work proposes a method based on the oxidation of antioxidants by triiodide. Antioxidant capacity was measured under controlled conditions such as concentrations of KI and KI3, and pH values. The amount of present antioxidants was determined by indirect spectrophotometric method, through which the excess triiodide ion remaining after reaction with antioxidants was quantified. For samples presenting inconveniences for spectrophotometric measurements, amperometric titration curves and bipotentiometric titration curves using a pair of platinum electrodes were proposed. The analytic methods with triiodide are simple, fast and useful for the quantification of most antioxidants. The antioxidant capacity (TAC) was determined in different samples such: tablets, capsules, green tea and orange juice. The TAC can be expressed as Trolox equivalents.