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  Home > JCE Print > Journal of Chemical Education > Issues > 2008  > August  >
In the Laboratory
Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid
An Undergraduate Analytical Chemistry Laboratory Experiment
Takashi Ito, D. M. Neluni T. Perera, and Shinobu Nagasaka
Department of Chemistry, Kansas State University, Manhattan, KS 66506
Cover
August 2008
Vol. 85 No. 8
p. 1112

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.
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Citation
Ito, Takashi; Neluni T. Perera, D. M.; Nagasaka, Shinobu. J. Chem. Educ. 2008, 85, 1112.
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Keywords
Analytical Chemistry; Electrochemistry; Food Science; Hands-On Learning / Manipulatives; Laboratory Instruction; Nanotechnology; Surface Science; Upper-Division Undergraduate; Vitamins
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History
Created:
Last Updated:
6/23/2008
7/2/2008
 Caution! 
Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations.
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