Electrochemical oxidation and voltammetric determination of tannic acid

The electrochemical oxidation of the tannic acid was studied by cyclic voltammetry with glassy carbon electrode in a solution containing 0.067 mol/L of supporting electrolyte KH2PO4-Na-2 HPO4. An irreversible oxidation peak of tannic acid at 0.31 V was observed in a potential range of 0.00 similar to + 1.00 V vs. SCE. The anodic current is linearly proportional to the concentration of tannic acid in the range of 1.0 x 10(-7) similar to 1.2 x 10(-5) mol/L. The detection limit is 1.3 x 10(-8) mol/L. Recovery tests of standard addition in Chinese gallnut samples showed an average recovery of 100.6%. The method is simple, rapid and sensitive with a relative standard deviation of 2.1% (n = 11) at 1.0 x 10(-6) mol/L level. The reaction mechanism is also discussed.