Extraction of Caffeine from Tea Leaves

Topics: Tea, Caffeine, Solubility Pages: 7 (2313 words) Published: December 29, 2012
This work describes the extraction of caffeine from tea leaves to determine its % caffeine. The extraction process selectively dissolves one or more compounds in a mixture into an appropriate solvent. In this experiment, it was visible in the process wherein the components of the tea leaves were dissolved in two solvents, water and dichloromethane (DCM), with DCM used for multiple extractions. The organic layer was evaporated and the determined % caffeine was 0.12%. Furthermore, the purified caffeine was subjected to sublimation process and melting point determination; the result was compared against the theoretical melting point of standard/pure caffeine (237°C). The process resulted in a melting point range of 225°C - 232 °C, which is less likely pure than the standard compound.

Caffeine is an alkaloid, a class of naturally occurring compounds containing nitrogen and having the properties of an organic amine base, purine. Caffeine, which is found in more than 60 plant species, belongs to a family of naturally occurring compounds known as xanthines [1]. The xanthines, which come from plants, are possibly the oldest known stimulants [3]. Caffeine is the most powerful xanthine in its ability to stimulate the heart, respiration, and the central nervous system. It is also a vasodilator (relaxes the blood vessels) as well as a diuretic (increases urination). Its use, however, can also cause nervousness, insomnia and headaches, and is physically addictive.

Caffeine is ingested by people in a number of things, from beverages like tea and coffee to medicines. Tea has been consumed as a beverage for almost 2,000 years, starting in China, thus, making it the most widely-consumed beverage around the world after water. It has a cooling, slightly bitter, astringent flavor which many enjoy. It is produced by steeping the young leaves and buds of the tea plant, Camellia sinensis, in freshly boiled water. Today, two principal varieties are used, the small-leaved China plant (C. sinensis var. sinensis) and the large leaved Assam plant (C. sinensis var. assamica). Hybrids of these two varieties are also grown. The leaves may be fermented or unfermented. Fermented teas are referred to as black tea, unfermented teas as green tea, and partially fermented teas as oolong [1,4],.

The caffeine content of some common goods and drugs Coffee 80 to 125 mg per cup
Coffee, decaffeinated 2 to 4 mg per cup
Tea 30 to 75 mg per cup
Cocoa 5 to 40 mg per cup
Milk chocolate 6 mg per oz
Baking chocolate 35 mg per oz
Coca-Cola 46 mg per 12 oz
Anacin, Bromo-Seltzer, Midol 32 mg per tablet
Excedrin, extra strength 65 mg per tablet
Dexatrim, Dietac, Vivarin 200 mg per tablet
Dristan 16 mg per tablet
No-Doz 100 mg per tablet

Caffeine does not exist alone in tea leaves; the leaves are mainly cellulose, pigments like chlorophylls, and tannins. Cellulose, a water-insoluble monosaccharide, is the structural component of the primary cell wall of green plants, which makes it rigid and less vulnerable to lysis. Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria and is vital for photosynthesis. Other pigments are also found in plants. Tannins are phenolic compounds of high molecular weight that have certain properties common with caffeine. Since tea leaves are compose of mixture of compounds, caffeine should be isolated from that mixture. One technique used to separate a specific compound in a mixture is called extraction. Extraction is a process that selectively dissolves one or more of the mixture compounds into an appropriate solvent. The solution of these dissolved compounds is often referred to as the extract. Extraction involves mixing of mutually insoluble materials, where a component of one of the phases moves into the other. Extractions are often classified according to the nature of the phases involved. The water-tea leaves system is an...
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