Determination of Tocopherol Using Reduced Graphene Oxide-Nafion Hybrid-Modified Electrode in Pharmaceutical Capsules and
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Determination of Tocopherol Using Reduced Graphene Oxide-Nafion Hybrid-Modified Electrode in Pharmaceutical Capsules and Vegetable Oil Samples Hayati Filik 1 & Asiye Aslıhan Avan 1 & Sevda Aydar 1 & Şeyda Çakar 1
Received: 22 May 2015 / Accepted: 4 November 2015 # Springer Science+Business Media New York 2015
Abstract The Nafion/graphene nanocomposite electrodes showed excellent electrochemical reactivity toward the oxidation of α-tocopherol, which permitted the highly sensitive detection of α-tocopherol. The optimal experimental conditions for the oxidation of α-tocopherol were achieved in acetone/acetate buffer solution and acetone/room temperature ionic liquid solution. The oxidation peak current of αtocopherol was also a linear relationship in the concentration range 0.5–90 μM with a detection limit of 0.06 μM in both the solvent systems. The electrode reaction of α-tocopherol (TOH) is an irreversible process which occurs readily in the presence of water in the solvent. Regarding analyte response, the acetone/acetate systems gave a higher analyte response than the acetone/room temperature ionic liquid systems. Ascorbic acid in less than 2000-fold excess does not interfere. Moreover, the hybrid electrode surface has very good reproducibility and stability. The sensing procedures were applied to the quantification of the α-TOH in different pharmaceutical formulations and vegetable oil samples. In addition, the developed method can be applied for the determination of αTOH in alpha-TOH-beta-carotene (ATBC) drinks.
Keywords Voltammetry . Graphene . Tocopherol . Vitamin E . Antioxidants . Vegetable oil . Pharmaceutical analysis
* Hayati Filik [email protected] 1
Department of Chemistry, Faculty of Engineering, Istanbul University, 34320 Avcılar, Istanbul, Turkey
Introduction Vitamin E is a collective name for tocopherols (TOH) and tocotrienols. There are eight main compounds which have vitamin E activity. These eight compounds are available in two varieties which are tocotrienols and TOHs (Sen et al. 2007). The biological role of tocotrienols, as minor components in vitamin E, has been largely underestimated despite studies showing their unique physiological functions. In fact, tocotrienols possess similar structures to TOHs characterized by a chromanol head named by α, β, γ, or δ according to the position and degree of methylation (Sen et al. 2007; Nesaretnam 2008). α-TOH is the most common of the group of TOHs, the others being α-, γ-, and δ-TOH. α-TOH is called vitamin E, which has many important functions in your consistency. TOHs (α-, γ-, and δ-) are natural phenolic antioxidants present in vegetable oils and are responsible for many of the healthful properties of these foods. TOHs are essential compounds; i.e., the body cannot synthesize. As examples, good sources of TOH include fruits, milk, vegetables, and vegetable oils (Feng et al. 2013). Vegetable oils are an important source of TOHs (Saldeen and Saldeen 2005). They have a high nutritional value and also help to prevent oxidation of lipids, which
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