Caffeine extraction from the commercial tea leaves (Lipton Yellow Label Tea) that was done is multiple extraction. 4 tea bags were used in the experiment; tea leaves were weighed having 8.5333 grams. The leaves were boiled in a beaker with 150ml of water; the aqueous tea extract was transferred in a seperatory funnel mixed with DCM (20ml), done thrice. The DCM layer was washed with 20ml 6M NaOH in the seperatory funnel; the organic layer was dried with anhydrous Na2SO4. The dried organic layer turned into crude caffeine was purified in a sublimation set-up. A capillary tube was used to insert the pure caffeine to determine its melting point, having 228°C - 229°C. The purified caffeine from the sublimation set-up was weighed having 0.0007g; using the wt. of the sample and the wt. of the pure caffeine, the %yieldwas determined, 8.20 x 10 -3 %.
The objectives of the experiment are to isolate, purify and characterize caffeine from tea leaves. The caffeine must be also purified, by using the sublimation set-up in the latter part of the experiment. The experimenters also need to determine the purity of caffeine by using the determined melting point.
Caffeine is the compound that is responsible for the stimulating action of coffee and tea. It is an example of an alkaloid; a group of organic compounds containing nitrogen. They are produced by plants and have physiological actions. Chemically, they are weak organic bases. Coffee beans contain less caffeine than tea leaves when weighed dry, but a serving of coffee contains roughly twice the caffeine of tea leaves. Caffeine has a bitter taste; hence, the flavor of the coffee and tea we consume came from tannins and flavoring agents of the substance.
Along with nicotine and alcohol, caffeine is one of the three most widely used mood –affecting drugs in the world. Caffeine is a potent quick acting drug which inhibits the stress effect in our bodies. A hit of caffeine could cause insomnia, increased blood pressure, and faster heart rate. Caffeine is a diuretic, which promotes urination that could cause dehydration.
Some people avoid the consumption of caffeine for its several health concerns. The experiment is somewhat similar to the industrial process of decaffeination, which is the removal of the 97% of the caffeine in a sample, for instance, the tea leaves.
The setups that were used in the experiment were assembled as shown in figures 1.1, 1.2. and 1.3
RESULTS AND DISCUSSION
This experiment was aimed to show the principle behind extraction. Extraction is a process that relatively dissolves one or more mixture of compounds into an appropriate solvent. In the case of the experiment, the solvent that was used to dissolve the mixture of compounds was the DCM (Dichloromethane). The solution of these dissolved compounds is called an extract.
Extraction includes the removal of soluble compounds from a solid matrix, same as what happens in brewing coffee or tea, and decaffeinating coffee by some commercial industries. Extraction refers to the transfer of soluble compounds to one liquid to another liquid, also known as liquid-liquid extraction.
The combined layer of DCM was washed by 20 ml 6M NaOH. Washing is the reverse process of extraction. The principle behind washing is removing the impurities in the second solvent to have a desired compound in the original solvent. In the experiment, the desired compound was caffeine.
DCM was used to extract caffeine from the aqueous tea extract, because caffeine is more soluble in dichloromethane (140 mg/ml) than it is in water (22 mg/ml). The tannins that were also present in the aqueous tea extract were converted into its salt form, after the three multiple extraction, by adding sodium carbonate. Sodium sulfate was also added to remove excess water in the organic layer.
Weight of tea leaves: 8.5333g
Melting point of Pure Caffeine: 228°C - 229°C
Pre-weighed watch glass: 50.6363g
Weight of coffee on watchglass: 50.63g
caffeine : 50.6363 – 50.63= 0.0063g
A process that can be used to determine the content of a certain substance within a solution is called extraction. However, each extraction process is different. To take only one example, the extraction of Caffeine from various substances, such as tea, coffee, and soft drink, requires different extraction techniques, since the composition of the solution is different in each case.
The caffeine that was taken from the tea leaves were somewhat green in color compared to the pure white powder substance of the pure caffeine. The green color means that other compounds were still present in the crude caffeine.
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The first step was to get the tea leaves from the tea bag, then weigh using the analytical balance. After weighing, pour back the leaves in the tea bags then boil it for 5 mins (~150ml of water)
The product after boiling the leaves was the Aqueous Tea extract. The other components of the tea leaves were extracted by pouring DCM (Dichloromethane) inside the seperatory funnel. The DCM was used thrice (Multiple Extraction), then all the DCM layers (Organic Layer) were combined.
The aqueous layer was discarded
The combined organic layer was washed with 20 ml of 6M NaOH in the seperatory funnel.
The NaOH layer was discarded
The organic layer was dried by using the anhydrous Na2SO4. The layer was placed on the evaporating dish and covered it with holed foil. The evaporating dish with the layer was placed in a locker and left it overnight.
The DCM evaporated. The layer turned into crude caffeine. The dried layer of caffeine in the evaporating dish was scraped using a spatula and it was pulverized by using the mortar and pestle.
The crude caffeine was placed in a sublimation setup (figure 1.1). Then it was heated until the caffeine was completely purified and turned into a crystal-like solid.
The pure caffeine that was subjected to sublimation was weighed.
Pure caffeine was placed in an oil bath to determine its melting point.
The weight that was obtained from the pure caffeine and the weight of sample were used to determine the %yield.