Extraction of Caffeine
Extraction of Caffeine from Tea Leaves Jaybee Balilea, Sharmaine Baysic, and Maria Anjelette Patricia Belen 3BIO7, Department of Biology, University of Santo Tomas, Manila, Philippines Abstract Extraction is a technique for isolating and purifying organic substances. In this technique, a solution is combined thoroughly with a second solvent that is immiscible with the first solvent. The solute is extracted from one solvent into the other because it is more soluble in the second solvent than in the first. In this experiment, there were two types of extraction used and these were the Liquid-liquid extraction and Solid-liquid extraction.
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Liquid-liquid extraction involves a liquid solvent to remove a liquid component from liquid while Solid-liquid extraction allows soluble components to be removed from solids using a solvent. These two types of extraction were used to extract caffeine from tea leaves (Thea sinensis). Caffeine belongs to the group of compounds known as Alkaloids. Alkaloids are a diverse group of compounds that are found in plants and contain basic nitrogen atoms. There were three methods used in extracting caffeine from tea leaves. These were isolation, purification and characterization of caffeine.
Based on the calculations made and with the use of these three methods, a caffeine percentage of . 05% and melting point range of standard caffeine and purified caffeine, 27°C and 20°C, respectively were obtained. Introduction Extraction is a separation technique that involves selectively removing one or more components of a solid, liquid, or a gaseous mixture into a separate phase . The substance being extracted is separated between two immiscible combined phases, and the ratios of its distribution between the phases depend on the relative solubility of the solute in each phase.
A type of extraction, Liquid-liquid extraction is a process used in isolating and purifying products from chemical reactions. This technique includes distributing a solute between two immiscible liquids. The immiscible liquids normally encountered in the organic laboratory are water and some organic solvent. This process can be considered a competition between two immiscible liquids for the distribution of solute. Another type of extraction used in this experiment is Solid-liquid extraction. This is a process of removing soluble components from solids using solvent.
Caffeine is a natural product belongs to the group of compounds called Alkaloids  . It stimulates respiration, the heart and the central nervous system, is a smooth muscle relaxant and a diuretic. In the experiment, tea leaves were use to extract caffeine. Usually in tea leaves there are 30 to 75 mg per cup caffeine. This experiment aims to isolate, to purify, to characterize caffeine from tea leaves and to calculate the percentage yield of caffeine from tea leaves. Results and Discussion The experiment was divided into three parts: isolation, purification and characterization.
In isolation part, Lipton yellow label tea leaves were used. And these was pre-weighed and extracted in boiling 100 ml distilled water for 5 minutes. Boiling water was used so that tea leaves swell to release caffeine and other compounds such as tannins. Then the extract in a flask were cooled with use of running tap water and it was transferred in a separatory funnel containing 20ml of CH2Cl2. Dichloromethane was used to selectively extract the caffeine from the water which retains most of the other organic compounds. In this experiment, solubility is the principle behind extraction.
The separatory funnel was shook gently to make sure that the solvent moves along the tea leaf particles to extract all the caffeine. The stopcock of the separatory funnel was opened while shaking to release any pressure building up inside. After shaking, the CH2Cl2 lower layer was drained into a clean flask and this shaking and draining was repeated 3 times until all drained CH2Cl2 lower layer was washed with 6M Sodium Hydroxide (NaOH). Sodium Hydroxide was used to ensure that other substances which are slightly soluble to dichloromethane are removed by converting them to their salts that remain in the water.
The Dichloromethane extract was dried with anhydrous salt (Na2SO4). Anhydrous salt is a catalyst which speeds the drying up of the extract. After that, simple distillation was used and the crude caffeine was obtained. Table 1. Isolation of Caffeine | Weight in grams| Weight of Tea Leaves| 10. 2508g| Weight of Empty Round Bottom Flask| 44. 4257g| Weight of Round Bottom + Crude Caffeine| 44. 4716g| Weight of Crude Caffeine| 0. 0459g| This table shows that the crude caffeine obtained was 0. 0459 g. The % crude caffeine was obtained using this formula : % crude caffeine= weight of crude caffeine weight of tea leaves x 100.
With the use of the values in the table (weight of crude caffeine=0. 0459g, and weight of tea leaves= 10. 2508g) and the % crude caffeine formula, the % crude caffeine was 0. 45%. In the purification part, the residue resulted from simple distillation undergone sublimation with the use of the purification set-up. Sublimation is a process of transition from solid phase to gas phase. The result of sublimation which was the sublimate also known as the purified caffeine was used in the determination of caffeine’s melting point which is the characterization part.
Also two capillary tubes, glass tubing, the characterization set-up were used in determining the melting point. Also in the characterization set-up, oil bath was used as a temperature regulator. Table 2. Purification of Caffeine Pre-weighed vials| 21. 4026g| Weight of vials + sublimate| 21. 4128g| Weight of sublimate| 0. 0102g| With the use of the values above, the weight of the tea leaves and with the use of this formula % caffeine = weight of sublimateweight of tea leaves x 100, the obtained % caffeine is 0. 05%. Table 3. Melting Point Determination Temperature 1| Temperature 2| Temperature RangeT2-T1| A. Standard Caffeine| 200 °C| 227°C| 27°C| B. Purified Caffeine| 180°C| 200°C| 20°C| Table 3 shows the temperature where the standard caffeine and the purified caffeine liquefy. Temperature 1 is the temperature when the standard caffeine and the purified caffeine started to liquefies. On the other hand, temperature 2 is the temperature where the standard and purified caffeine were completely melted Fig. 1 Example of separatory funnel Experimental Three Lipton yellow label tea bags were used and the weight of the tea leaves was pre-weighed.
The leaves were placed tea bags again and were boiled in distilled water (100ml) for 5minutes. Then the extract was left for cooling down. After that, the tea extract was transferred in a separatory funnel containing 20ml Dichloromethane. The funnel was carefully shaken three times with the stopcock left open to release the pressure inside the funnel. The lower layer of the Dichloromethane (DCM) was drained into a clean flask. The shaken as well as the draining of the DCM were repeated thrice. The DCM extracts were combined and placed again into the separatory funnel. It was then washed with NaOH solution.
NaOH layer was removed and the DCM layer was drained into a clean dry beaker containing a half spatula of anhyd Na2SO4. Solution was agitated to let Na2SO4 settle. The solution together with the anhydrous salt was left in the locker to dry up. After allowing it to dry up, the crude caffeine was scraped from the container and was transferred in a filter tube with the fitted inner test tube that served as a cold finger and for at least 35minutes. The cold finger was constantly refilled with ice water. Inner tube was gently removed. Caffeine clinging in a cold finger was scraped off and was transferred in a vial.
Then percent yield caffeine was calculated and the weight of the sublimate was also noted. Using mortar and pestle, caffeine crystals were crushed into a very fine powder. One end of a micro capillary was sealed by heating while rotating it at a 45 degree angle from the blue portion of a Bunsen burner flame. Pulverized caffeine was scooped using the open end of the micro tube. Caffeine were packed well at the bottom of the tube by letting it fall inside a one meter long glass tubing and letting it bounce up and down a table top. Same was done on the standard caffeine. Both standard and caffeine samples were tied against a thermometer.
Thermometer was clamped and dipped a beaker filled with cooking oil. Cooking oil was heated with the Bunsen burner flame. Cooking oil was constantly stirred to evenly distribute the heat. Temperature range was recorded between the first appearances of liquid within the sample to the disappearance of the last traces of solid. Appendix % crude caffeine= weight of crude caffeine weight of tea leaves x 100 % caffeine = weight of sublimateweight of tea leaves x 100 Group 2 % crude caffeine= 0. 0459g10. 2508g x 100= 0. 45% % caffeine= 0. 0102g10. 2508g x 100= 0. 05% Temperature range= T2-T1 A. Standard Caffeine 27°C – 220°C = 27°C B. Purified Caffeine 200°C- 180°C= 20°C References  Gilbert,J. & Martin S. , “Organic Chemistry Lab Experiments”. 5th edition, Cengage Learning, USA,©2011, pp. 73  Engel R. , Kriz G. , Lampman G, & Pavia, D. , “Introduction to Organic Laboratory Techniques, A Small Scale Approach”. 3rd edition, Cengage Learning, USA, © 2011, pp. 452  Retrieved on July 11, 2011 from World Wide Web: http//chem. -courses. ucsd. edu/coursepages/uglabs/143A_weizman/expt_3N. pdf  Retrieved on July 11, 2011 from World Wide Web: http//ochemonline. pbworks. com/f/05_caffeine. pdf