Novel approach for the voltammetric evaluation of antioxidant activity using DPPH-modified electrode

•Voltammetric characteristics of DPPH immobilized on the electrode surface is studied.•DPPH/CeO2-CPB/GCE gives reversible one electron highly sensitive radical reduction.•DPV on DPPH/CeO2-CPB/GCE is developed for the antioxidants activity evaluation.•Natural phenolic antioxidants and medicinal herbs extracts are investigated.•Good agreement of DPV and standard method data is obtained.

The electrochemical behavior of 2,2-diphenyl-1-picrylhydrazyl (DPPH) immobilized on the electrode surface has been studied. Bare glassy carbon electrode (GCE) and modified with dispersions of CeO2 nanoparticles in water (CeO2-H2O/GCE) and cationic surfactant cetylpyridinium bromide medium (CeO2-CPB/GCE) has been investigated as a platform for the DPPH immobilization. The best voltammetric characteristics (peak potential separation of 70 mV, system reversibility with currents ratio of 0.98 and the highest peaks currents) have been observed on CeO2-CPB/GCE. The effect of CeO2 nanoparticles concentration has been evaluated. Scanning electron microscopy and electrochemical impedance spectroscopy have been applied for the electrode characterization. DPPH/CeO2-CPB/GCE has been used for the estimation of the antioxidants activity of natural phenolic antioxidants (quercetin, tannin, catechin and ferulic acid) expressed as the EC50 parameter according to differential pulse voltammetric (DPV) data. The EC50 decreased in the following order: quercetin (29 ± 1 μM), tannin (29 ± 4 μM), catechin (117 ± 4 μM) and ferulic acid (731 ± 17 μM). These data are in a good agreement with the results of standard spectrophotometric determination. The developed approach has been successfully applied for the antioxidant activity evaluation of medicinal herbs tinctures, infusions and decoctions.

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