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A novel electrochemical method for selective determination of antioxidant activity based on 2,2-diphenyl-1-picrylhydrazyl j 2,2-diphenyl-1-picrylhydrazin (DPPH · j DPPH) redox couple and biamperometric technique is proposed. Two identical glassy carbon disk electrodes were mounted in a classic electrochemical cell and the tested working potential difference was between 50 and 200 mV. The DPPH · j DPPH redox couple exhibited a high degree of reversibility. Selectivity of detector was tested by different antioxidant compounds in ethanol-phosphate buffer solution, pH 7.40. The results of antioxidant activity of pure antioxidant compounds and of actual samples of beverages, expressed as Trolox equivalents and determined by proposed biamperometric and spectroscopic measurements, were in good correlation (R ¼ 0.9959). The detection limit for Trolox established by the applied biamperometry was 0.05 mM while the resulting current was linear up to 25 mM of Trolox.

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