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1996
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In the Laboratory
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The Extraction of Caffeine from Tea: A Modification of the Procedure of Murray and Hansen
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Andreas Hampp
Department of Chemistry and Biochemistry, University of California-Los Angeles, 405 Hilgard Ave, Los Angeles, CA 90095
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December 1996
Vol. 73 No. 12
p. 1172
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| Abstract |
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According to the literature published, the "Extraction of Caffeine from Tea" is certainly one of the most common experiments in undergraduate laboratories. The extraction was generally done using chloroform (1 - 3), or methylene chloride (4 - 7), solvents known as possible human carcinogens. A recent publication by S. D. Murray and P. J. Hansen reports a less toxic alternative through the use of 1-propanol (8). However, in following the procedure given, we noticed that the crude caffeine obtained after evaporation of 1-propanol was highly contaminated with tannins and sodium chloride. In many cases we observed difficulties redissolving the brownish, sometimes oily residue for further purification.
We introduced an additional cleaning/extraction step, which is commonly performed in organic synthesis. It consists of a wash with a 10% aqueous NaOH solution to extract tannins and sodium chloride from 1-propanol and subsequent drying with sodium sulfate anhydrous prior to evaporation. The average yield of crude caffeine is unaffected and the product is obtained as a yellowish powder.
This slight variation of Murray and Hansen's procedure is currently used in our first-year chemistry laboratory classes and clearly shows a higher student success rate in the isolation crude caffeine. The experiment described here is performed in a three-hour lab period, which is followed by sublimation and characterization through melting point and infrared spectroscopy on a second day.
Literature Cited
- Helmkamp, G. K.; Johnson, H. W. Selected Experiments in Organic Chemistry, 2nd ed.;
Freeman: San Francisco, 1968; pp 157-158.
- O'Connor, R. The Freeman Library of Laboratory Separates in Chemistry; Birdwhistell, R. K.;
O'Connor, R., Eds.; Freeman: San Francisco, 1971; Vol. 2.
- Pavia, D. L.; Lampman, G. M.; Kriz, G. S.; Introduction to Organic Laboratory
Techniques; Saunders: Philadelphia, 1976; pp 58-62.
- Williamson, K. L. Macroscale and Microscale Organic Laboratory, 2nd ed.; Heath:
Toronto, 1989; pp 130-133.
- Mayo, D. W.; Pike, R. M.; Butcher, S. S. Microscale Organic Laboratory, 2nd ed.;
Wiley: New York, 1989; pp 162-164.
- Nimitz, J. S. Experiments in Organic Chemistry; Prentice-Hall: Englewood Cliffs, NJ,
1991; pp 61-62.
- Landgrebe, J. A. Theory and Practice in the Organic Laboratory, 4th ed.; Brooks/Cole:
Pacific Grove, CA, 1993; pp 381-383.
- Murray, S. D.; Hansen, P. J. J. Chem. Educ. 1995, 72, 851-852.
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| More Information |
 Citation |
Hampp, Andreas. J. Chem. Educ. 1996 73 1172.
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Keywords |
Laboratory Instruction
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History |
Created:
Last Updated: |
August 5, 1999
February 21, 2006
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