Tea Leaves Extraction

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Extraction of Caffeine from Tea Leaves
1: Introduction
The purpose of this experiment is to extract caffeine from tea leaves using different solubility characteristics of caffeine in different solvents. The technique used in this experiment is liquid-liquid extraction. Caffeine are known stimulants that has physiological effects on humans such increasing alertness and reducing tiredness and sleep. This organic substance is also a diuretic and causes vasodilation of blood vessels. There are side effects of caffeine with high dosage such as insomnia and headaches and prolong usage may lead to dependence on caffeine. Caffeine can be found in tea leaves, coffee, kola nuts and cocoa beans with varying amounts. About 5% of the leaf weight comprises
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Caffeine, tannins (phenolic substances) and a little chlorophyll can also be found in tea leaves. Hot water extraction can be used to separate caffeine from the tea leaves (mainly cellulose) as water can form hydrogen bonds with water and solubilise (water has higher solubility at higher temperatures). However, tannins are also water soluble but they display acidic properties instead. Thus, a basic salt like sodium carbonate can be added to bind to tannins to form a salt. Although now both the tannins salt and caffeine are water soluble, using an organic solvent, dichloromethane, renders tannins salt insoluble. Caffeine is more soluble in dichloromethane (14g/100g) than in water (2g/100g). Caffeine will dissolve in the dichloromethane phase while tannins salts remain in the aqueous phase. Addition of sodium sulphate will act as a drying agent and evaporation of the dichloromethane solution would yield pure caffeine which is white in…show more content…
However, the percentage yield and melting points did not meet the expected results. 0.812% caffeine yield of crude caffeine was obtained, which is much lower than the expected percentage yield of 5%. The melting point of the caffeine obtained, 221 ºC, was also lower than the expected melting point of crude caffeine which is 238 ºC. This shows that the caffeine obtained is not pure and there were possible mistakes that occurred during the experiments that caused caffeine loss.

One of the possible reasons for the poor result could be that the techniques were basic. We used a hot water extraction, and organic solvent extraction and a rotary evaporator technique which could not have given us crude caffeine. Further purification steps needs to be conducted in order to obtain crude
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