Extraction of Caffeine from Tea Leaves
Essay by Dana Hipolito • April 22, 2017 • Lab Report • 1,127 Words (5 Pages) • 2,288 Views
Extraction of 1,3,7-Trimethylpurine-2,6-dione from Thea Sinensis
Angela Maye J. Gelit, Mirsadhe Gail T. Gonzales, Dana Marelli L. Hipolito*, & Milchan Mike E. Juico
Department of Psychology, College of Science, University of Santo Tomas, España Boulevard, 1015 Manila, Philippines
Abstract
Caffeine is a xanthine alkaloid compound that acts as a stimulant in humans and is the most commonly used stimulant in the world. The experiment aims to isolate & purify caffeine from tea leaves, to characterize caffeine using thin-layer chromatography, and to calculate the percentage caffeine of tea leaves. Dichloromethane was used to extract caffeine from tea leaves, and was purified using sublimation. Thin-line chromatography was performed to verify the purity of the caffeine.. The crude caffeine is has an Rf value of 0.56 with some impure spots visible, and the percentage of the caffeine of tea leaves is 0.076%.
Introduction
[pic 1][pic 2]
Caffeine is the most commonly used stimulant in the world and is present in a variety of products such as coffee, tea, soft drinks, and energy drinks. It is also present in chocolate, and energy bars [1]. Caffeine is a xanthine alkaloid, which is an organic compound made of carbon, hydrogen, nitrogen, and oxygen ( see Figure 1) that are often derived from plants such as tea leaves [2]. Caffeine is sometimes called theine when found in tea.
Caffeine is also sold as over-the-counter medications, for xanthine alkaloid acts as stimulants to the central nervous system (CNS) of humans. This stimulant has the effect of increasing alertness[3], vigilance, and physical performance. Caffeine blocks receptors in the areas of the brain that control arousal and motivation. In moderate, caffeine dosed up to 200mg improved cognitive performance to individuals who are either rested, sleep-deprived, or fatigued [1].
The experiment aims to isolate & purify caffeine from tea leaves, to characterize caffeine using thin-layer chromatography, and to calculate the percentage caffeine of tea leaves.
Methodology
Prior to the actual experimentation, 3 teabags were weighed in a 50-mL pre-weighed beaker to obtain the weight of the tea leaves. On the actual experimentation, the teabags are then boiled in 100mL distilled H2O for 5 minutes. After the said duration, the boiled teabags were cooled then 2 ice cubes were added.
Once it was completely cooled, the tea mixture was transferred to the separatory funnel with added 20mL dichloromethane. The mixture shall be extracted from two immiscible layers, a dichloromethane layer and an aqueous layer. The aqueous layer was extracted from the mixture and another 20mL of dichloromethane was added again to the previous dichloromethane layer. These procedures are to be repeated once more before discarding the aqueous layers of each step. The dichloromethane layer are collected in an Erlenmeyer flask and then transferred again to the separatory funnel. The dichloromethane layer was washed using 20mL 6M sodium hydroxide. Two layers, the dichloromethane layer and the NaOH layer, should be visible. The NaOH layer is to be discarded. The dichloromethane layer was transferred to a 125mL Erlenmeyer flask. A half spatula of anhydrous Na2SO4 was added to the mixture and decanted to a pre-weighed evaporating dish. The mixture was covered with aluminum foil. It was made sure that the cover had holes on it.
After approximately 2 days, the mixture had hardened in the evaporating dish. The evaporating dish is to be weighed to calculate the weight of the caffeine. The caffeine was grinded for it to become crude. The crude caffeine is to be used in chromatography with the purpose of knowing its purity.
Results & Discussion
Table 3.1 summarizes the results obtained from the experiment. Table 3.2 shows the computations made for the experiment.
Table 3.1: Extraction of caffeine from tea leaves | |
Weight of Tea Leaves | 6.2078 g |
Weight of empty evaporating dish | 120.2828 g |
Weight of evaporating dish + caffeine | 120.2875 g |
Weight of caffeine | 0.0047 g |
% caffeine | 0.076% |
Rf value of crude coffee | 0.56 |
Rf value of standard caffeine | 0.60 |
Table 3.2: Computations | |
Weight of caffeine = (wt. of evap. dish + caffeine) – (wt. of evap. dish) = 120.2875g – 120.2828g[pic 3] = 0.0047g | % Caffeine = [wt. of caffeine ÷ wt. of tea leaves] x 100 = [0.0047g ÷ 6.2078g] x 100 = 0.0751 x 100[pic 4] = 0.0076% |
Rf value of crude caffeine = spot center ÷ distance from solvent front = 2.7 ÷ 4.8[pic 5] =0.56 | Rf value of standard caffeine = spot center ÷ distance from solvent front = 2.9 ÷ 4.8[pic 6] = 0.60 |
One of the problems with the isolation is that caffeine does not exist alone in tea leaves but is accompanied by other natural substances from which the principal structural material of all plant cells, such as tannins and chlorophylls. Tannins are phenolic compounds having molecular weights between 500 and 3000. They precipitate alkaloids and proteins from aqueous solutions.Caffeine is water-soluble and is one of the main substances extracted into the tea solution. Caffeine constitutes as much as 5% by weight of the leaf material in plants.
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