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

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Takashi Ito , D. M. Neluni T. Perera and Shinobu Nagasaka

Department of Chemistry, Kansas State University, Manhattan, KS 66506

J. Chem. Educ., 2008, 85 (8), p 1112

DOI: 10.1021/ed085p1112

Publication Date (Web): August 1, 2008

Abstract

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.

Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Analytical Chemistry

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Electrochemistry

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Measuring Vitamin C Content of Commercial Orange Juice Using a Pencil Lead Electrode
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Journal of Chemical Education2010 87 (5), 507-509
- Measuring Vitamin C Content of Commercial Orange Juice Using a Pencil Lead Electrode
  David King, Jeffrey Friend and James Kariuki
  Journal of Chemical Education2010 87 (5), 507-509
  A pencil lead successfully served as an electrode for the determination of ascorbic acid in commercial orange juice. Cyclic voltammetry was used as an electrochemical probe to measure the current produced from the oxidation of ascorbic acid with a variety ...
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