Redox Behavior of Riboflavin and Its Determination in Real Samples at Graphene Modified Glassy Carbo

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Physical Chemistry Communications, Volume 3 Issue 2, October 2016 www.bacpl.org/j/pcc

Redox Behavior of Riboflavin and Its Determination in Real Samples at Graphene Modified Glassy Carbon Electrode Atmanand M. Bagoji and Sharanappa T. Nandibewoor* P. G. Department of Studies in Chemistry, Karnatak University, Dharwad‐ 580003, India *Corresponding Author ‐Sharanappa T. Nandibewoor P. G. Department of Studies in Chemistry, Karnatak University, Dharwad‐ 580003, India E‐mail: stnandibewoor@yahoo.com Tel: +91 8362215286; fax: +918362747884 Abstract Improved electrochemical oxidative determination of riboflavin (RF) at a thin graphene film modified glassy carbon electrode (GF‐GCE) has been established using cyclic and differential pulse voltammetric techniques. The graphene was characterized by SEM, TEM and electron diffraction studies. The surface area calculated for modified electrode was higher than the glassy carbon electrode which is responsible for more catalytic activity in the present system. Cyclic voltammetry was employed to unveil the electrocatalytic performance of graphene and two redox peaks were observed for RF with good intensity. The redox voltammetric behavior of RF at the sensor was quasi‐reversible involving two electrons‐two protons. At the surface of modified electrode, the redox reaction was adsorption‐controlled. A probable electro‐redox mechanism was proposed. Under the optimum conditions, a calibration curve of longer linearity for peak current and RF concentration in the range from 1.0 nM to 1.5 × 10‐8 M was obtained with a detection limit of 1.0 × 10‐10 M. The present method was applied to riboflavin determination in pharmaceutical and real samples with good recovery. There was no interference from any excipients, which indicates the specificity of the composite electrode. Furthermore, the fabricated RF chemical sensor exhibited excellent stability, remarkable catalytic activity and reproducibility towards RF determination. The method finds applications in clinical laboratory. Keywords Riboflavin; Voltammetry; Graphene; Oxidation; Analytical Applications

Introduction Riboflavin (RF) (Scheme 1) is a natural, yellow, essential water‐soluble vitamin. RF is ampiphilic in nature due to the presence of hydrophilic ribityl side chain as well as hydrophobic isoalloxazine ring [1]. RF takes an important role in the formation of two coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These coenzymes are responsible for the redox reactions by accepting and donating two electrons in the isoalloxazine ring [2]. These redox reversible reactions are necessary for cellular respiration and energy supplementation [3]. RF also plays vital role in promoting growth, immunity, cancer prevention, cell regeneration and antioxidation [4, 5]. R N

O

N

NH N O R - C5H11O4 SCHEME 1 CHEMICAL STRUCTURE of RIBOFLAVIN

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Redox Behavior of Riboflavin and Its Determination in Real Samples at Graphene Modified Glassy Carbo by Shirley Wang - Issuu