Monday , 27 March 2017

Nano-Al2SiO5/ Graphite Paste Sensor Fabrication: It’s Use in Voltametric Estimation of Ascorbic Acid in Localy Consumed Vitamin-C Formulations

R.C. Saini*1, Mekonen Tirfu1, Rishi Pal2, Abraha Tadese1, Azanaw Girmaw Mengistu3 
1*Department of Chemistry, College of Natural & Computational Sciences, Mekelle University, P.O. Box 231, Mekelle, Ethiopia.
2SBMN Institute of Pharma Sci & Res, Baba Mastnath University, Asthal Bohr-124021, India 
3Department of Chemistry, Dire Dawa University, Dire Dawa, Ethiopia

The carbon paste modified with aluminum silicate was utilized to develop a new sensor and applied for the study of the electro catalytic oxidation and voltammetric determination of the ascorbic acid in locally used general medications. Differential pulse voltammetric method was used to study the electrochemical properties of AA using electrode. It was found that the anodic peak current increased more than two fold in magnitude in presence of the modifier rather than in pure carbon paste. Optimizations of the parameters have been made at the best electrode composition of 15% AS, 62.5% graphite and 22.5% paraffin oil. A sensitive, simple and time-saving procedure has been developed for the analysis of AA in the linear range 5μΜ to 100μM with a detection limit 1.20μM and quantification limit 5.73μM. The irreversible anodic oxidation process at interface follow   both the diffusion controlled as well as surface controlled mechanism at modified electrode surface at high pulse period. The two electrons and two protons oxidation scheme for AA has also been proposed. The validity of this technique was tested on quantification of ascorbic acid in three commercial pharmaceutical products (Limcee, Beconzym C forte tablets and Capsule) directly and after spiking the sample solutions with known quantity of analyte. The observed results showed a good agreement with reported amount of ascorbic acid in these pure and spiked samples.
Keywords: Ascorbic acid, Aluminum silicate, Carbon paste electrode, Differential pulse voltammetry, Electrochemical oxidation

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