Isolation of Caffeine from Tea and Thin Layer Chromatography of Analgesic

Isolation of Caffeine from Tea and Thin Layer Chromatography of Analgesic

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Isolation of Caffeine from Tea and Thin Layer Chromatography of Analgesic CH221 Lab 19 February 2008 Introduction The primary objective of this lab was to isolate caffeine from tea with dichloromethane and to purify the caffeine by means of sublimation. Thin Layer Chromatography was used to determine the identity of three unknown over the counter analgesics and to determine the composition of Excedrin. Caffeine (as seen above) is a compound found in tealeaves. Also found in tealeaves, is the compound tannin. When tealeaves are boiled with a mixture of water and sodium carbonate (Na 2 CO 3 ), a sodium salt of tannins separates from the caffeine. Because tannins and caffeine are water soluble, both will be extracted from the tealeaves. In order to remove pure caffeine, nonpolar CH 2 Cl 2 is added to the tannin/caffeine mixture. Tannins cannot dissolve in CH 2 Cl 2 , but caffeine can. Since there is a difference in the density of CH 2 Cl 2 and water (1.3g/mL and 1.0g/mL respectively), the CH 2 Cl 2 become the bottom layer and contains only caffeine, and the top layer, water, contains only tannins.
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