Reactions of superoxide anion radical with antioxidants and their use in voltammetry

Kinetic parameters were calculated for the electrochemical reduction of oxygen at a glassy-carbon electrode with the generation of superoxide radical anions in a 0.05 M solution of (C2 H5 ) 4NI in dimethylformamide in the presence of fat-soluble antioxidants, retinol and α-tocopherol. A procedure based on the protonation of the radical anion with antioxidant molecules is proposed for the voltammetric determination of antioxidants to determine milligram amounts of retinol and α-tocopherol in model solutions (RSD = 1-2%). The calibration graphs for retinol and α-tocopherol are linear in the concentration ranges 9.7 ×10-5 -2.3 × 10-3 and 6.2 × 10-4 -3.1 × 10-3 M, respectively. The detection limits for retinol and α-tocopherol are 4.8 × 10-5 and 4.1 × 10 -4 M, respectively. The procedure was applied to the determination of the active component (retinol and α-tocopherol) in pharmaceuticals.