ABTS^•+ radical cation-based new potentiometric approach for the studying of antioxidant capacity

The potentiometric approach for the studying of total antioxidant capacity, based on the use of the cation radical of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), is proposed. Conditions for non-enzymatic generation that enable the formation of a cation radical/reduced form system, subsequently employed as a potential-determining system have been established. The ratio of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) to ammonium persulfate was 1:0.5; the solvent was 0.1 M KCl and ethanol (1:1); generation (25 ± 2 °C) was carried out for 24 hours. It was shown that the system remains stable in the solid state for at least one month after drying at 70 °C. Individual antioxidants, plant extracts, and model biological fluids were investigated using the developed potentiometric approach. No statistically significant differences were observed between the results obtained by the classical spectrophotometric method and the proposed potentiometric method; the F- and t-tests did not exceed their critical values. Plant extracts with initial coloration and a model whole blood sample were investigated in the absorption range of the ABTS cation radical, which had previously been problematic using the spectrophotometry.