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2007
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In the Laboratory
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A New Colorimetric Assay of Tabletop Sweeteners Using a Modified Biuret Reagent
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An Analytical Chemistry Experiment for the Undergraduate Curriculum
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Christopher J. Fenk and Nathan Kaufman
Department of Chemistry, Kent State University Tuscarawas Campus, New Philadelphia, OH 44663
Donald G. Gerbig, Jr.
Department of Biological Science, Kent State University Tuscarawas Campus, New Philadelphia, OH 44663
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October 2007
Vol. 84 No. 10
p. 1676
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| Abstract |
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A new, fast and effective colorimetric analysis of the artificial sweetener aspartame is presented for application in undergraduate laboratory courses. This new method incorporates the use of a modified biuret reagent for selective detection and analysis of aspartame in aqueous solutions. The modified reagent is less caustic than the traditional biuret reagent, which allows it to be used in an effective and simple assay of artificial tabletop sweeteners. Sample preparation is readily accomplished in three steps: (i) addition of the analyte to a 10.00 mL volumetric flask, (ii) addition of modified biuret reagent, and (iii) dilution with water. The modified biuret reagent consists of 60 mmol copper(II) sulfate pentahydrate dissolved into a solution containing 210 mmol potassium sodium tartrate and 500 mmol sodium carbonate. Spectroscopic analysis in the visible region of the electromagnetic spectrum (629 nm) allows for use of inexpensive and readily available laboratory instrumentation. The entire experiment may be completed in about two hours, giving the instructor ample time for discussion of artificial sweeteners, the Beer–Lambert Law, and coordination chemistry, when applied during a typical three hour laboratory period.
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| Supplement |
Instructions for the students. including detailed background material and post-lab questions, are available.
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| More Information |
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Citation |
Fenk, Christopher J.; Kaufman, Nathan; Gerbig, Donald G., Jr. J. Chem. Educ. 2007, 84, 1676.
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Keywords |
Amino Acids; Analytical Chemistry; Consumer Chemistry; Coordination Compounds; Crystal Field / Ligand Field Theory; First-Year Undergraduate / General; Food Science; Hands-On Learning / Manipulatives; High School / Introductory Chemistry; Inquiry-Based / Discovery Learning; Laboratory Instruction; Qualitative Analysis; Quantitative Analysis; Second-Year Undergraduate; UV-Vis Spectroscopy
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History |
Created:
Last Updated: |
8/20/2007
9/7/2007
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 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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