DC polarographic examination of Hg2+ reduction applicability to antioxidant activity determination

ABSTRACT Direct current polarographic (DCP) antioxidant assay based on the decrease of anodic limiting current of HydroxoPerhydroxoMercury(II) Complex [Hg(O 2 H)(OH)] (HPMC) upon addition of antioxidants (AOs) was verified. Here, influence of several common AOs on DCP cathodic currents of both HPMC and Hg 2+ was followed. Amperometric titrations of HPMC and Hg 2+ with AOs and potentiometric titrations of Hg 2+ were performed. The changes of DCP i-E curves and limiting currents decrease during amperometric titrations, as well as end points of amperometric and potentiometric titrations for each AO used as titrant proved the occurrence of Hg 2+ reduction, either from complex (HPMC) or salt (HgCl 2 ) solution. Constant H 2 O 2 reduction current during amperometric titration of HPMC further confirmed the participation of Hg 2+ as the oxidant species in reaction with AOs. The possibility of determining AO activity of flavonoids, phenolic acids, ascorbic acid and Trolox based on the decrease of Hg 2+ reduction current was demonstrated. Strict correlation (R 2  = 0.96) between a new AO assay named MRAP (Mercury Reduction Antioxidant Power) and HPMC assay was found. Total AO capacity of real samples was measured by the proposed fast, simple and inexpensive MRAP assay as well.