Potentiometry in determining the antioxidant capacity of compounds of different hydrophilicity in the joint presence using mixed solvents and surfactants

In this work, for the first time, the potentiometric method was used to determine the antioxidant capacity (AOC) of compounds of different hydrophilicity in the joint presence using mixed solvents and surfactants. The AOC of model solutions of antioxidants of different hydrophilicity was determined separately and in the joint presence in the media of phosphate buffer-surfactant and mixed solvents–surfactant, using as an example the ascorbic acid and the α-tocopherol. It was shown that the surfactant Triton X-100 is able to solubilize α-tocopherol under the selected conditions, allows to obtain reproducible and accurate results, and has less effect on the equilibrium rate of the K₃[Fe(CN)₆]/K₄[Fe(CN)₆] system. Phosphate buffer-ethanol and phosphate buffer-acetonitrile media in the 3:2 ratio with Triton X-100 (5 mmol/dm³) were chosen as the analysis conditions (RSD ≤ 6%). The range of determined concentrations was (0.006–0.5) m mmol/dm³ in phosphate buffer-ethanol and (0.006–0.3) m mmol/dm³ in phosphate buffer-acetonitrile. AOC of raw materials infusions was determined in selected media. The positive correlation with the well-known Folin-Ciocalteu assay was obtained.

Graphical abstract