Organic Chemistry : Isolation of Caffeine from a Tea Bag - Lab Report Example

Isolation of Caffeine from a Tea Bag Caffeine was isolated from tea bags using methylene chloride as the solvent of choice. 0.035g of caffeine was isolated from 4.699g of tea leaves from two tea bags. The percentage weight recovery of caffeine was calculated to be 0.74%. 1.0. Introduction The most common xanthine derivatives found in the human diet are caffeine, theobromine and theophylline found in tea coffee cocoa bean and chocolate (Cornelia, Adrian and Simona, 966). Xanthines are naturally occurring family of compounds known to possess stimulant properties. Green tea is one of the most famous beverages due to bioactive compounds associated with numerous benefits. Athletes have used it as an ergogenic aid to decrease fatigue and improve performance (Rafaela, 163). However, it is suspected of being associated with low birth weight, abortion, intrauterine growth retardation and an increased risk of premature membrane rupture. The physiological characteristics of xanthines make them compounds of interest (Branislava et al., 144). Figure 1 The structure of caffeine Caffeine is a component in tea and coffee that makes them valuable commodities. Caffeine (1, 3, 7-trimethyl xanthine) is an alkaloid nitrogen-containing compound with an organic base (Fang et al., 2278). Caffeine is a central nervous system, cardiac and respiratory stimulant that can also induce diuresis. Caffeine is suggested to be an environmental chemical indicator. Tea polyphenols are always contaminated with caffeine. Green tea has been found to have higher concentrations of caffeine compared to tea bags. However, teabags are more suitable for consumption due to their higher catechin content (Rafaela, 163). The first isolation of caffeine was in 1820’s. Caffeine is isolated from coffee beans using organic solvents. The solvents are then drained off, and beans steamed to remove residual solvent. Drying and roasting increases the flavor of the final coffee beverage. The removal of caffeine is called decaffeination and its intention in beverages are to reduce their caffeine content to between 0.03 to 1.2%. Conventional breeding, physicochemical methods, microbial degradation and genetic engineering are some of the methods employed in decaffeination (Fan et al., 2279). Three methods of extraction of caffeine are frequently used. The first is the direct contact decaffeination that uses organic solvent methylene chloride. The process removes the required caffeine and retains compounds necessary for the flavor. However, methylene chloride is toxic, and this is a major drawback. The second method is the water process where hot water and steam are used to remove caffeine and other soluble components. Passing the solution through activated charcoal filters removes caffeine. Water is not a selective decaffeinating solvent, therefore, most flavor oils are removed resulting in bland flavored coffee. Carbon dioxide decaffeination process is the third way in which the raw coffee is moistened with steam and water before being passed through an extractor with supercritical CO2 at high temperature and pressure that acts as a selective solvent for caffeine (Donald et al., 81). In tea leaves caffeine exists in combination with other components e.g. cellulose, tannins. Some like caffeine are water soluble whereas others e.g. cellulose is insoluble. Solid-liquid extractions and liquid extractions are some of the methods used by organic chemists in extraction (Ruchi et al., 194). The species, season, age of leaves and horticultural practices affect the composition of tea. 2.0. Methods 2.1 Introduction Methylene chloride is both volatile and soluble in water. Caffeine has higher affinity of methylene chloride, therefore, easily dissolves compared to water. The caffeine will have a greater attraction for the organic methylene chloride solvent and the hydrogen bonds between caffeine and water will be broken. The addition of sodium sulfate changes the chemical structure of garlic acid. Gallic acid is converted to a phenol salt that is insoluble in methylene chloride yet soluble in water. Using separating apparatus, the two immiscible solutions can be separated. One will contain the caffeine in methylene chloride and the other the water soluble components. Evaporation will be final method of recovering the caffeine from the methylene chloride solution. Methylene chloride has low boiling point around 400C 2.1. Materials and reagents Table 1 Materials and reagents Name Molecular formula MW (g/mol) MP/BP (0C) Density (gcm-3) Toxicity Amount used Methylene chloride 84.93 -96.7 39.75 1.33 30ml Caffeine C8H10N4O2 194.2 258 0.499g Sodium carbonate Na2CO3 105.99 851 2.54 0.5g Anhydrous sodium sulfate Na2SO4 142.06 888 1100 2.664 2.2. Procedure 20ml of water was measured into a 50ml beaker. The beaker was covered with a watch glass and the water heated to a boil on a hot plate. Two tea bags were carefully opened, and the tea leaves measured before being put back into the bags care taken not to spill any tea leaves. The tea leaves were then completely immersed in the boiling water, and the watch glass replaced. Heating was continued for a period of 15 minutes. The tea bags were squeezed on the inside wall of the beaker to ensure all liquid seeped out into the solution. The concentrated tea solution was then transferred into two centrifuge tubes using a Pasteur pipette while ensuring that the volume of liquid in each centrifuge tube is equal. 0.5g of sodium carbonate was added to the hot liquid in each of the centrifuge tubes. The tubes were then capped and agitated gently to mix and dissolve the solids. The tea solution was cooled to room temperature. 3ml of methylene chloride was added into each centrifuged tube using a Pasteur pipette. The centrifuge tubes were capped and shaken for several seconds to ensure a homogeneous mixture. The tubes were then vented to release pressure caution taken that no liquid squirts out of tubes. The mixture was shaken for 30 seconds with occasional venting. The mixture was centrifuged for several minutes to separate the layers and break the emulsion. The centrifuge process was continued until no emulsion remained. Using a Pasteur pipette, the lower organic layer was removed and transferred into a test tube. 3ml of methylene chloride was then added to the remaining aqueous layer in the centrifuge tube, capped and shaken for a second extraction. The layers were separated, and each organic layer from the second extraction added to the first. Granular anhydrous sodium sulfate was added to dry the organic layer, and the mixture stirred with a spatula to break any clumps. Additional drying agent was added with stirring and the mixture left to stand for 10 to 15 minutes with occasional stirring. The dry methylene chloride was then transferred using a Pasteur pipette into a dry pre-weighed Erlenmeyer flask. The methylene chloride was evaporated by heating in a hot water bath at 40 0C . The crude caffeine coated the bottom of the flask. Heating was stopped immediately methylene chloride was evaporated to prevent sublimation of caffeine. The Erlenmeyer flask containing the caffeine was then weighed, and weight recorded. The percentage weight recovery was then calculated, and a stopper placed on the flask and its contents stored. Sublimation was the method employed to purify the caffeine. 1ml of methylene chloride was added to the Erlenmeyer flask, and the solution transferred to a sublimation apparatus using a dry Pasteur pipette. A few drops of methylene chloride were added to Erlenmeyer flask to rinse out the caffeine completely. The percentage weight recovery was then calculated and compared against the initial value (Donald et al., 80-82). 3.0. Results A standard Lipton tea bag is approximated to weigh 2.0 ± 0.05 g. Each tea bag is expected to contain 0.055g of caffeine, therefore, two tea bags will have 0.11g of caffeine (Julia, 1). From the experiment, the mass of tea leaves in the tea bags were 2.402g and 2.297g respectively adding up to a total of 4.699g. The empty 50ml Erlenmeyer flask weighed 50.095g whereas the flask containing the caffeine extract weighed 50.130g. Therefore, the amount of isolated caffeine (actual yield) is the difference in these two measurements (0.035g). Mass of caffeine = 50.130 - 50.095 = 0.035g The percentage amount of caffeine contained in 4.6669g of tea leaves (≡ 2 tea bags) was calculated as below. The percentage weight recovery was found to be 0.745% by weight. Weight percentage recovery = by weight Therefore, only, 31.81% of the theoretical yield was isolated. 4.0. Discussion 0.035g of caffeine was isolated from the two teabags weighing 4.699g. This is only 0.745% by weight of the tea leaves weight (Figure 2). It is evident that the caffeine was less than 1% of the total components of the tea leaves. This value falls within the 0.03 to 1.2% expected for decaffeinated caffeine beverages. Figure 2 Amount of caffeine isolated from 4.699g tea leaves The isolated actual caffeine was 31.81% of the theoretical yield. According to Linda (1) this yield is acceptable considering various constraints of the isolation process. One is in the separation of the caffeine containing methylene solution from the water solution where so as not to taint the extract, not all the methylene solution was separated out. The large soapy bubbles (emulsions) that formed between the methylene chloride solution and water solution was also another likely reason for low yield as it could not permit accurate separation of the mixtures. The method of isolation could also have inherent errors contributing to a lower yield. Loss could be in the process, caffeine that sublimed in the evaporation process. 5.0. Conclusion Caffeine was successfully isolated from tea leaves. The isolated caffeine was less compared to the theoretical yield. However, no confirmation was made as to the identity of the isolated compound. UV/vis spectrophotometry or HPLC would have been suitable methods for confirming the identity of the compound. Like in most organic extraction processes the yield was not 100 %. Methylene chloride as a solvent in the extraction of caffeine from tea leaves has been shown to be effective than other methods which were used to compare yields. Caffeine is more soluble in methylene chloride because they are both organic compounds. Caffeine can dissolve in water, but its affinity for methylene chloride is greater. Sodium sulfate alters the chemical structure of garlic acid that would otherwise interfere with the isolation of caffeine as it has a little affinity for methylene chloride. Work Cited Branislava Srdjenovic, Vukosava Djordjevic-Milic, Nevena Grujic, Rade Injac, and Zika Lepojevic. “Simultaneous HPLC Determination of Caffeine, Theobromine, and Theophylline in Food, Drinks, and Herbal Products”. Journal of Chromatographic Science 46 (1): 2008. Print. Fan, F.-Y, Y Xu, Y.-R Liang, D Borthakur, J.-L Lu, and X.-Q Zheng. "Isolation and Characterization of High Caffeine-Tolerant Bacterium Strains from the Soil of Tea Garden." African Journal of Microbiology Research 5.16 (2011): 2278-2286. Print. Oliveira, Rafaela M. M. D. "Quantification of Catechins and Caffeine from Green Tea (camellia Sinensis) Infusions, Extract, and Ready-to-Drink Beverages." Food Science and Technology (campinas) 32.1 (2012): 163-166. Print. Ruchi Verma, Lalit Kumar. “Characterization of Caffeine Isolated from Camellia Sinensis Leaves of Sikkim Himalayan Region”. J. Chem. Pharm. Res. 2(4) 2010: 194-198. Print. Cornelia, Purcărea Adriana Chiş, Simona Vicaş and Alexandrina Fodor. “Comparative studies about caffeine content in Roasted ground coffee and in china black tea.” Analele Universitatii Din Oradea Fascicula 2 (7) 2008: Julia Trimble. Isolation of Caffeine from Tea Leaves. Web. 20th November, 2014. http://www.odinity.com/isolation-caffeine-tea-leaves/ Donald Pavia, Gary Lampman, George Kriz, Randall Engel (2010). A Small Scale Approach to Organic Laboratory Techniques, third edition. 80-85 copyright 2010 Cengage writing. Read More