Evaluation of antioxidant capacity by bipotentiometric titrations

摘要

There are different methods for measuring the total antioxidant capacity of a sample. This work proposes a method based on the oxidation of antioxidants by triiodide. Antioxidant capacity is measured under controlled conditions such as concentrations of KI and KI_3, and pH value. In spectrophotometric method, the amount of present antioxidants can be determined by indirect calibration curves, through which the excess triiodide ion not reacting with antioxidants is evaluated. For samples presenting inconveniences for spectrophotometric measurements, amperometric titration curves and bipotentiometric titration curves using a pair of platinum electrodes are proposed. The analytic method with triiodide is simple, fast and useful for the quantification of most antioxidants. The total antioxidant capacity (TAC) can be expressed in Trolox equivalents.