Determination of Ascorbic Acid by Electrocatalytic Voltammetry with Methylene Blue

Abstract

A rapid voltammetric method was developed for the determination of l-ascorbate using methylene blue as a mediator with a glassy carbon electrode. The magnitude of the peak current that occurs near −0.04 V vs. Ag/AgCl is proportional to l-ascorbate concentration in the range of 1.2 × 10⁻⁶ to 1.12 × 10⁻³ M. The limit of detection is 1 × 10⁻⁶ M. Eight replicate analyses of 5.0 × 10⁻⁵ M and 4.5 × 10⁻⁴ M l-ascorbate yielded RSD values of 1.9 and 1.6%, respectively. The method was applied to the determination of ascorbic acid in fruit juices and vitamin C tablets.

Keywords:

• Ascorbic acid
• Methylene blue
• Electrocatalysis

Acknowledgments

The author expresses his highest gratitude to Prof. Susan R. Mikkelsen for supporting him during stay at the University of Waterloo, and also, the National Science and Engineering Research Council of Canada, Department of Chemistry of University of Waterloo and Isfahan University of Technology that provided funding for this work.