Isolation of Caffeine from Tea Leaves

Topics: Solubility, Caffeine, Tea Pages: 6 (1966 words) Published: September 7, 2013
Extraction of Caffeine from Lipton® Tea Leaves

Nathaniel Camangon*, Kaila Bumagat, Franz Mari Burgos, Remigio Callanta Department of Chemistry, College of Science, University of Santo Tomas, Manila, Philippines

Abstract
This experiment mainly focuses on the extraction of pure caffeine by multiple extraction from commercially acquired tea leaves and determining its purity by melting point determination. A 0.02% yield of pure caffeine was obtained from 10.4978g of tea leaves (4 tea bags). The acquired pure caffeine’s purity was determined by melting point and was found to have a melting point range of 3℃. The temperature range of the melting point will serve as the basis of purity of the pure caffeine.

Introduction
Caffeine is a bitter substance found in coffee, tea, soft drinks, chocolate, kola nuts, and certain medicines. It has many effects on the body's metabolism, including stimulating the central nervous system. This can make us more alert and gives us, as well, a boost of energy. [1] And like most adults, caffeine has been a part of our daily routine. But do we know the caffeine content of our favorite drink? We may want to take a look at just how much caffeine we get in a typical day, especially if we’re bothered by restlessness, anxiety and the likes. According to the American Academy of Pediatrics, it is only recommended that adolescents gets no more than 100 mg of caffeine a day. [2] In this lab we will extract and purify caffeine from tea leaves. First water soluble compounds will be extracted from dry tea leaves with boiling water. Then, caffeine will be preferentially extracted from the water into organic solvent. The solvent will be removed and the crude material will be purified by sublimation

This experiment has the following objectives: (1) to isolate caffeine using multiple extraction, (2) to purify caffeine using sublimation, (3) to determine the purity using melting point and (4) to calculate the % yield of the crude purified caffeine.

The experiment used multiple extraction instead of using simple extraction.  Extraction process, in general, selectively dissolves one or more of the mixture compounds into a suitable solvent. The solution of these dissolved compounds is referred to as the extract. Here the organic solvent dichloromethane is used to extract caffeine from an aqueous extract of tea leaves because caffeine is more soluble in dichloromethane (140 mg/ml) than it is in water (22 mg/ml). However, the tannins that are slightly soluble in dichloromethane can be eliminated by converting it to their salts (phenolic anions by adding sodium carbonate) (tannins are phenolic compounds of high molecular weight and being acidic in nature can be converted to salts by deprotonation of the -OH group) which remain in the water [3]. Multiple extraction makes use of usually two, three, or four extractions of the aqueous layer with an organic solvent and is carried out in sequence in order to remove as much of the desired product from the aqueous layer as possible. The effectiveness of multiple small volume extractions versus one large volume extraction can be demonstrated by a simple calculation [4].

Sublimation is adopted by chemists as a purification technique. There are many advantages for performing sublimation over other purification methods. This process is principally used for micro scale purifications of solids because the loss of product is typically very minimal. Furthermore, this technique is appropriate for any heat sensitive compound (but under high vacuum, sublimation can be affected under low temperatures). Thirdly, unlike recrystallization, solvents are not involved at all in the process, and most traces of any solvent are effectively eliminated. However sublimation is only favored over crystallization, when the substance weighs less than 100mg [5], and has the correct properties. Based on the theory of this phase change, the process is highly dependent on the different vapor...


References: [1] Caffeine: MedlinePlus. (n.d.). National Library of Medicine - National Institutes of Health. Retrieved July 17, 2013, from http://www.nlm.nih.gov/medlineplus/caffeine.html
[2] The Mayo Clinic diet: eat well, enjoy life, lose weight. (2010). Intercourse, PA: Good Books.
[3] Extraction of Caffeine from Tea (Theory) : Biochemistry Virtual Lab II : Biotechnology and Biomedical Engineering : Amrita Vishwa Vidyapeetham Virtual Lab . (n.d.). Amrita Vishwa Vidyapeetham Virtual Lab . Retrieved July 18, 2013, from http://amrita.vlab.co.in/?sub=3&brch=64&sim=169&cnt=1
[4] Liquid/Liquid Extraction. (n.d.). PSU Chemistry. Retrieved July 17, 2013, from courses.chem.psu.edu/chem36/Experiments/PDF 's_for_techniques/Liquid_Liquid.pdf
[5] Chemistry Online @ UTSC. (n.d.). Information & Instructional Technology Services | Information & Instructional Technology Services. Retrieved July 17, 2013, from http://webapps.utsc.utoronto.ca/chemistryonline/sublimation.php
[6] Engel, R. G. (2011). Introduction to organic laboratory techniques: a small-scale approach (3. ed., International ed.). Singapore: Brooks/Cole, Cengage Learning.
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