THE EXTRACTION OF CAFFEINE FROM CONCENTRATED LIPTON BLACK TEA
Debra Jones
Abstract:
In this experiment, caffeine was extracted from Lipton black tea. Two teabags were used, and each teabag had 55 mg of caffeine. 18 mg of caffeine was extracted from the tea. The percent yield of caffeine from this experiment was 32.73%, and the percent error was determined to be 67.27%.
Introduction:
Caffeine is an alkaloid, meaning that it contains nitrogen and has the properties of an organic amine base. In the world, there are over 60 plants that contain caffeine. These plants include guarana, yoco, and mate (Barone and Roberts, 1984). Caffeine is an important staple in many people’s everyday life. This stimulant has been consumed by humans all over the world for hundreds of years. A majority of caffeine consumption (54%) comes from coffee. The second most consumed caffeinated product (43%) is tea. It is estimated that the average person consumes about 70 mg of caffeine daily (Gilbert , 1984), thus making it the most widely consumed stimulant worldwide (Laurientiet al, 2002).
Besides being found in food and drinks, caffeine is also used therapeutically. It can be used to help tame acne, migraine headaches, infant apnea, and much more. The body’s response to caffeine is dependent on the concentration of caffeine found in the product that is being consumed or administered (Barone and Roberts, 1984).
There are many different methods for extracting caffeine, including the using methylene chloride, water, ethyl acetate, supercritical or liquid carbon dioxide, and a few other substances. All of these methods are able to extract the caffeine due to the concentration gradient between the caffeinated substance and the solution that it is in (COSIC) .Two methods for extracting caffeine include liquid-liquid extraction and sublimation. Liquid-liquid extraction separates different liquids based on their difference in solubility. Sublimation extraction purifies a compound through a direct phase change from solid to gas. In this study, caffeine was extracted from a solution containing two bags worth of Lipton black tea.Dicholormethane and liquid-liquid extraction were used in order to isolate caffeine from the tea solution.
Figure 1 Caffeine molecule.
4. Materials and Methods:
2 grams of sodium carbonate was added to 15 mL of water. The resulting solution was then heated on a hot plate. Once the solution started to boil, a Lipton Black tea teabag was immersed in the solution for 5 minutes. After seeping, the teabag was removed, and the water was squeezed from it, and the solution was again heated until it boiled. A second Lipton teabag was added and was allowed to steep for 5 minutes. Again, the excess water was removed from the teabag. The concentrated tea was transferred to a 15 mL centrifuge tube and was allowed to cool on an ice bath. Once the tea was below 40 ⁰C, 2 mL of dichloromethane was added to the centrifuge tube to begin caffeine extraction. The tube was repeatedly inverted in order to extract the caffeine. After extraction was complete, the bottom organic layer was removed, but the emulsion layer was not touched. This process was repeated two more times. After all of the organic material was removed, the remaining caffeine was left to dry for two days. The remaining caffeine was then weighed.
Results:
The data collected during experimentation included the amount of water used, the weight of sodium carbonate, the weight of the beaker that held the caffeine, and the combined weight of the beaker and caffeine (Figures 2 and 3). The weight of the isolated caffeine was found to weigh 0.018g. This weight was found by subtracting the weight of the beaker from the combined weight of both the caffeine and the beaker (Equation 1).
Weight of Caffeine= Weight of caffeine and beaker – weight of beaker (Equation 1)
Weight of Caffeine= 27.825g – 27.807g
Weight of Caffeine= 0.018 g
Data Table:mL of Water / 15 mL
Weight of Sodium Carbonate / 2.085 g
Weight of Beaker / 27.807 g
Weight of Beaker and Dried Caffeine / 27.825 g
Figure 2 Raw data collection
Data Table:Weight of Caffeine / 0.018 g
Theoretical Yield / 55 mg
Figure 3 Weight of extracted caffeine and Theoretical Yield
Percent Yield= (Actual Yield/Theoretical Yield)x 100 (Equation 2)
Percent Yield= (18 mg/55 mg)x100
Percent Yield= 32.73%
Percent Yield of caffeine was determined to be 32.73% (Equation 2), and the percent error was calculated to be 67.27% (Equation 3).
Percent error= (Actual – Theoretical)/ Theoretical X 100 (Equation 3)
Percent error= (18 mg -55 mg)/ 55 mg X 100
Percent error = 67.27%
Discussion:
Caffeine is an alkaloid, meaning that it is an organic, non-polar compound that contains nitrogen, hydrogen, and carbon(Ashiharaet al, 2008). Alkaloids have an amine group and are produced by many organisms, including coffee and tea plants from which caffeine is extracted.
Caffeine is 2.2 mg/mL soluble in water at 25⁰C, 180 mg/mL at 80⁰C, and 670 mg/mL at 100⁰C. At lower temperatures, caffeine is not very soluble in water. However, at higher temperatures, the bonds in caffeine allow it to dissolve in water.
Before boiling the water, sodium carbonate was added. The sodium carbonate is a salt that essentially acts as a buffer. Tea leaves are acidic, and caffeine is basic, so in order to maintain the same pH, sodium carbonate is needed.
After the second teabag was finished steeping, the tea is cooled to 40⁰C in an ice bath. This is because dichloromethane was going to be added to the solution, and dichloromethane has a very low boiling point. So to ensure that the dichloromethane didn’t boil, the tea was cooled.
Dichloromethane was added in order to separate the caffeine from the organic material. Dichloromethane was used because caffeine is soluble in it while the organic material is not. This allows the organic material and the caffeine to be separated into two separate layers. Dichloromethane was used three times in order to isolate as much caffeine as possible. It was important not to shake the solution too vigorously when dichloromethane was added or else emulsions would be created and complete separation of the organic material and the caffeine would not have been achieved.
Emulsions are small drops of one liquid that are dispersed in a liquid that they are not soluble in (Taylor, 1934). In order to remove emulsions, the solution would need to be centrifuged. Once emulsions were removed from the solution, the caffeine was extracted from the organic material. The top water layer contained organic material and water, and the dichloromethane layer contained the caffeine and dichloromethane. The dichloromethane layer is below the water layer because it is denser than the water and the organic material. It is from this layer that the caffeine is extracted from. Both dichloromethane and caffeine are non-polar, so the forces between the two substances are London-dispersion forces. In the water layer, there was hydrogen bonding between the water and the organic material due to the water’s polarity.
Calcium chloride was used as a drying agent because it easily forms hydrates at low temperatures. It is an effective drying agent because it is a salt, so it takes up water readily. It generally doesn’t bind to hydroxyl, amino, and carbonyl groups, which also makes it effective in this scenario. Drying agent was added in small amounts. Once the solution was translucent, a sufficient amount of drying agent had been added. Once this was finished, the remaining solution was left in the fume hood so that the dichloromethane would evaporate, leaving only the powdered caffeine.
The sublimation and the liquid-liquid extraction techniques allow one to separate specific substances from solutions. The liquid-liquid extraction is used because it allows for the extraction of a desired substance form a solution that has many other dissolved components in it. Sublimation is also ideal for extraction because it allows for extraction of high purity compounds. It is ideal for small amounts of compound and solution.
For the extraction of the caffeine, the percent recovery was 32.73%, and the percent error was determined to be 67.27%. One source of error was when dichloromethane was added and the tube was being inverted, some of the solution spilled out. This could have resulted in some loss of caffeine. Another possible source of error could be that if too much drying agent was added, a loss of product could have occurred.
Conclusion
In this experiment, the percent recovery of caffeine was 32.73 % and the percent error was 67.27%. Compared to the experiments done by Wang et al. andTelloet al, the percent error in this experiment was relatively high. This is most likely attributed to the loss of some material during the extraction of the caffeine. This experiment could be furthered by using more techniques for caffeine extraction, including sublimation. It would be interesting to see the fluctuation between the different methods.
Citations:
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Barone, J. J., and H. Roberts."Human consumption of caffeine."Caffeine.Springer Berlin Heidelberg, 1984. 59-73.
Gilbert, R. M. "Caffeine consumption."Progress in clinical and biological research158 (1984): 185.
International Coffee Organization.Decaffeination.
Laurienti PJ, Field AS, Burdette JH, Maldjian JA, Yen YF, Moody DM. Dietary caffeine consumption modulates fMRI measures. Neurolmage 17(2): 751-757, 2002.
Taylor GI.The Formation of Emulsions in Definable Fields of Flow.Proc. R. Soc.Lond. A 146 (1934).
Tello J, Viguera M, Calvo L. Extraction of caffeine from Robusta coffee (Coffeacanephora var. Robusta) husks using supercritical carbon dioxide. LWT- Food Science and Technology [Online] 59 (2011): 53-60
Wang H, ChenL, Xu Y, Zeng Q, Zhang X, Zhao Q, Ding L. Dynamic microwave-assisted extraction coupled on-line with clean-up for determination of caffeine in tea. LWT-Food Science and Technology [Online] 44 (2011): 1490-1495
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