Use of DPPH⋅|DPPH Redox Couple for Biamperometric Determination of Antioxidant Activity

Abstract

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.

Genesis and development of DPPH method of antioxidant assay

“…c. Biamperometric determination of antioxidant activity A novel electrochemical method for selective determination of antioxidant activity based on DPPH ·/DPPH redox couple and biamperometric technique is proposed by Milardovic et al (Fig. 5) (Milardovic et al 2005). In this method, two identical glassy carbon disk electrodes were mounted in an electrochemical cell.…”

Electrochemical Methods for Total Antioxidant Capacity and its Main Contributors Determination: A review

“…The confirmed high selectivity of the biamperometric method allows the quantification of redox active analytes present in biological samples (urine, blood), and, also, of the total antioxidant capacity of foodstuffs and beverages [113][114][115][116]. Nevertheless, biamperometry requires very rigorous control of experimental conditions; the method's performances with respect to selectivity relying upon the specificity of the reaction between the oxidized or reduced form of the redox couple and the analyte [113][114][115][116].…”

“…The molar ratio DPPH•/DPPH should be carefully chosen: in studies using this redox couple, conditions were employed with a DPPH• concentration lower than the DPPH one, so the measured current intensity is limitated by the smaller concentration of the radical [23,114]. Antioxidant addition diminishes the concentration of DPPH• and increases the concentration of DPPH, thus giving rise to a current linearly dependent on antioxidant concentration [23,114].…”

“…Antioxidant addition diminishes the concentration of DPPH• and increases the concentration of DPPH, thus giving rise to a current linearly dependent on antioxidant concentration [23,114].…”

Electrochemical Pseudo‐Titration of Water‐Soluble Antioxidants

“…To assess the total antioxidant capacity (TAC) of not only one antioxidant species, but of a whole complex sample (e.g. blood and saliva), several methodologies have been employed such as, the trolox equivalent antioxidant capacity (TEAC), the ferric reducing/antioxidant power assay (FRAP), the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical test, the reducing antioxidant capacity evaluated (RACE) by electrolysis, among others [12,[17][18][19][20][21]. The main principle of such strategies is based on quantifying the concentration of AOs that can be consumed by a given amount of oxidative species and in some cases finding the equivalence between the signal obtained from the measured sample and a known AO concentration, for instance trolox.…”