Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid: An Undergraduate Analytical Chemistry Laboratory Experiment.

• Autores: Takashi Ito, D.M. Neluni T. Perera, Shinobu Nagasaka
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 85, Nº 8, 2008, págs. 1112-1115
• Idioma: inglés
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• Resumen

  • This article describes an undergraduate electrochemistry laboratory experiment in which the students measure the L-ascorbic acid content of a real sample. Gold electrodes modified with self-assembled monolayers (SAMs) of thioctic acid and cysteamine are prepared to study the effects of surface modification on the electrode reaction of L-ascorbic acid at neutral pH. Cyclic voltammograms of L-ascorbic acid are different on these electrodes, owing to the different surface charge of the SAMs. Cysteamine-modified electrodes give a sharper oxidation peak at a smaller overpotential and thus are more suitable for measuring the concentration of L-ascorbic acid in an aqueous solution. A linear calibration curve is obtained using such an electrode, permitting the determination of L-ascorbic acid content in a vitamin C tablet. This experiment provides a means for teaching the basics of voltammetry, teaching the effect of chemical modification of the electrode surface on the electrode reaction, and providing students with hands-on experience in fabricating and utilizing electrochemical sensors. Additionally, it can be completed within three hours and is suitable as an undergraduate laboratory experiment.