单宁的电化学氧化及伏安测定法

Electrochemical Oxidation and Voltammetric Determination of Tannic Acid

以玻碳电极（ＧＣＥ）为工作电极，ＫＨ２ＰＯ４－Ｎａ２ＨＰＯ４为支持电解质，通过循环伏安法首次观测到了单宁的不可逆氧化峰。在单宁浓度为１．０×１０～（－７）～１．２ × １０～（－５）ｍｏｌ／Ｌ范围内与其峰电流呈线性关系；检出限为 １．３×1０～（－８）ｍｏｌ／Ｌ。在中药五倍子浸提液中用标准加入法进行回收实验，其平均回收率为１００．６％。该法简便、快速，用１．０×１０～（－６）ｍｏｌ／Ｌ的单宁溶液重复测定１１次，ＲＳＤ为２．ｌ％。对其反应机理作了初步探讨。

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.