Electrochemical determination of tannic acid at glassy carbon electrode modified by antimony film

Abstract

Tannic acid (TA), a water soluble polyphenol compound has been investigated for many years, especially to cure many diseases1,2,3,4. Tannic acid (TA) is a natural polyphenolic compound, and it‟s widely used in food and medicine industry. Due to its wide range of applications, analysis of TA is important not only in food but also in the medical and environmental fields. TA is present commonly in the human diet including fruits and different kinds of vegetables and can be found in several beverages, including wine, beer, coffee, black tea and white tea. It is used as a food additive as clarifying agent, flavor adjunct and flavoring agent5 as well as additive in medical and veterinary fields due to its antimicrobial activity, anticarcinogenic and antimutagenic potentials and also antioxidant nature protect cellular oxidative damage6,7. Antioxidants may be defined as compounds that inhibit or delay the oxidation of other molecules by inhibiting the initiation or propagation of oxidizing chain reactions8. Antioxidants can also protect the human body from free radicals and have been widely used as food additives to provide protection against oxidative degradation of foods. The antioxidant activity of phenolic compounds is mainly attributed to their redox properties, which allow them to act as reducing agents, hydrogen donors and quenchers of singlet oxygen. Phytochemicals are secondary metabolites in plants that play important roles in their metabolism, defense mechanisms, and disease resistance. They are also widely recognized for their bioactive and health-promoting properties. The content of TA in fruits, tea and beer can strongly influence their taste, and hence, is an important parameter to evaluate and control the quality of these products. TA may combine with metals to form tannic acid-metal complexes which have a toxic potential to the root system of plants9. For these reasons, the determination of tannic acid has been of great importance. Several methods including spectrophotometry10, colorimetry11, liquid chromatography12 and chemiluminescence13,14,15 have been applied for the determination of TA content in the waters, pharmaceuticals and foods. Each method has its advantages and drawbacks. For example, chromatographic methods allow the determination of TA, but they are time consuming and expensive. However, these methods are costly, require highly skilled manpower, complicated and time consuming procedures which is difficult to use for TA analysis. Compared to these methods, the electrochemical method has several advantages such as its low cost, the options of analysis without extraction or preconcentration, highly selective and