Cyclic voltammetry, an electrochemical method, used to
determine tannic acid has previously been reported [13].
However, when sufficient positive potential was applied for
electrochemical oxidation of tannins, phenol and phenolic compounds
were reported to form an inhibitory layer on surfaces
of Pt, Au and glass carbon electrode [14–16]. Redox reaction
at the electrode is gradually blocked by the formatted layers,
which have high molecular weight and comprise oxidized mate