The electrochemical behavior of 2,2-diphenyl-1-picrylhydrazyl (DPPH center dot) 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 (CeO2CPB/GCE) has been investigated as a platform for the DPPH center dot 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 center dot/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 mu M), tannin (29 +/- 4 mu M), catechin (117 +/- 4 mu M) and ferulic acid (731 +/- 17 mu M). 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. (C) 2017 Elsevier Ltd. All rights reserved.