Extraction of Caffeine from Thea sinensis Abstract Extraction of Caffeine from Thea sinensis main objective is to isolate, purify characterized caffeine from tea leaves. Sublimation technique was used to get the % yield which is 0. 07%. The melting point of the standard caffeine with the sublimate is 229°C. Introduction The active ingredient that makes tea and coffee valuable to humans is caffeine. Caffeine is an alkaloid; a class of naturally occurring compounds containing nitrogen and having the properties of an organic amine base.
Caffeine is a naturally occurring alkaloid found in over 60 plant species. Caffeine belongs to a family of naturally occurring compounds known as xanthines. The xanthines, which come from plants, are possibly the oldest known stimulants. Caffeine is the most powerful xanthine in its ability to increase alertness, put off sleep and to increase ones capacity for thinking. Caffeine is a vasodilator (relaxes the blood vessels) as well as a diuretic (increases urination). Caffeine does not exist alone in tealeaves; the leaves are mainly cellulose, pigments and chlorophylls, and tannins.
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Tannins are phenolic compounds of high molecular weight that have certain properties in common. Some of the better-known plant sources are coffee and cocoa beans, tealeaves, and kola nuts. While coffee and tea are both popular products containing caffeine, the amounts vary widely in a single serving. To further confuse the matter, coffee beans contain less caffeine than tea leaves when measured dry. However, a serving of coffee contains roughly twice the caffeine of tea. Much of the flavor of coffee and tea comes from tannins and other flavoring agents.
Caffeine has a slightly bitter flavor. As a result, decaffeinating coffee beans and tea leaves will leave the flavor slightly changed even if no other compounds are lost. Beverage Caffeine (mg)/cup Coffee 80 – 125; Coffee, decaffeinated 2 – 4;Tea 30 – 75; Chocolate milk/cocoa 3 – 30; Soft drink 20 – 50 Several health concerns have been raised over the consumption of caffeine. The Food and Drug Administration (FDA) has extensively studied the consumption of caffeine and its health effects. In 1987 the FDA concluded that normal caffeine consumption does not increase risk to health.
These studies included cancer risk, coronary heart disease, osteoporosis, reproductive function, birth defects, and behavior of children. Many consumers prefer to avoid caffeine partially or altogether due to its stimulant effects and others still have health concerns. This makes decaffeinating coffee and tea an important industrial process. Decaffeination is also significant for the world’s economy; approximately eight billion pounds of coffee are grown a year making it second only to oil as an international commodity. It should be noted that decaffeinated coffee and tea are not caffeine free.
These products can be labeled decaffeinated as long as 97% of the caffeine has been removed. Results and Discussion Watch glass For isolation of bioactive molecules found in the tea bags, two extraction set-ups were used; the solid-solid extraction and liquid-liquid extraction. 250 ml beaker with 100 ml water Hot plate 3 tea bags Figure 1 Solid-Liquid Extraction Set-up Erlenmeyer flask Separatory funnel Figure 2 Liquid- Liquid Extraction Set-ups The sample Thea sinensis (tea leaves) weighs 6. 4448 g. The dry tea leaves were extracted (Figure 1).
The water extract was transferred into the separatory flask with CH2Cl2. The purpose of dichloromethane is to remove all impurities that the mixture is dissolved in a suitable solvent such as poured into a separatory funnel (Figure 2). An aqueous solution of the acid or base is added, and the pH of the aqueous phase is adjusted to bring the compound of interest into its required form. After shaking and allowing for phase separation, the phase containing the compound of interest is collected (crude caffeine). Figure 3 Sublimation Set-up
The crude caffeine’s crystallization (Figure 3) was one of the crucial stages in the experiment because once the cold water penetrated the filter tube, the chances are the caffeine crystals will get wet and it cannot be used anymore. The solubility of caffeine in water is not a highly water soluble substance. C8H10N4O2 has 4 Nitrogens and 2 Oxygens, all of which are highly electronegative. H2O can bond with hydrogen to caffeine at these six locations. The hydrogen of the water is attracted to the highly electronegative N and O atoms. This makes caffeine soluble in water.
It is quite soluble in dichloromethane, the solvent used in this experiment to extract the caffeine from water. Caffeine can be extracted easily from tea bags. The procedure one would use to make a cup of tea – simply “steeping” the tea with very hot water for about 7 min – extracts most of the caffeine. There is no advantage to boiling the tea leaves with water for 20 min. Since caffeine is a white, slightly bitter, odorless, crystalline solid, it is obvious that water extracts more than just caffeine. The weight of the pure caffeine during the experiment is 0. 0043 g using equation 1 (appendix).
The percent yield is 0. 07 % was calculated using equation 2 (appendix). 2 Capillary tubes: 1: standard – 1: standard & 1 sample Beaker with 100ml oil Tripod stand Wire gauze Bunsen burner Iron clamp Iron stand Thermometer Figure 4 Melting Point Determination Set-up | Standard Mix of Caffeine| Standard Mix of Caffeine and Sublimate Caffeine| T1 (temperature started)| 220°C| 225°C| T2 (temperature ended)| 229°C| 229°C| Table 1 Melting point of Pure Caffeine Table 1 shows that the standard mix of caffeine with sublimate caffeine started melting with a higher temperature compare to the standard caffeine alone.
The standard melting point of the caffeine is between 234–235 °C (monohydrate). [2] The standard melting point of the caffeine(1st capillary tube) & standard mix of caffeine with sublimate caffeine during the experiment (2nd capillary tube) and the standard melting point have a huge difference. The factors that could affect the melting point are the oil and the heat in the Bunsen burner. The 100ml oil was used for the melting because unsaturated vegetable fats and oils can be transformed through partial or complete hydrogenation into fats and oils of higher melting point. [1]
Caffeine (C8H10N4O2) Alkaloids are bitter tasting, natural nitrogen-containing compounds found in plants. The basic property of alkaloids comes from the lone pair of electrons found on at least one nitrogen. Alkaloids are often found to have potent physiological activity. Tea leaves contain tannins, which are acidic, as well as a number of colored compounds and a small amount of undecomposed chlorophyll (soluble indichloromethane). To ensure that the acidic substance remains water soluble and that the caffeine will be present as the free base, sodium carbonate is added to the extraction medium.
In order to successfully extract any substance from one solvent into another, we must maximize differences in solubility. Adding base to the solution has a second important effect. The water solution contains much more than just caffeine, and some of these compounds are also soluble in dichloromethane. Making the solution basic forms insoluble tannin salts which removes them from the solution before the caffeine is extracted. Experimental Extraction, 3 teabags were opened and took the combined weights of tea leaves. The tealeaves were returned in the bags and secured with staple wire.
The group boiled the teabags in 100ml water for 5 minutes. After 5 minutes, the tea bags were removed and the 2 ice cubes were placed in the tea extract to cooling to room temperature. The group transferred the tea extract in a separatory funnel containing 20 ml of CH2Cl2 to extract the caffeine. The pressure from the separatory funnel was constantly released. The CH2Cl2 lower layer was drained into a clean flask. The adding of CH2Cl2 in the separatory funnel was repeated twice. (CH2Cl2 X 2). All the drained CH2Cl2 were combined in the flask. The water layer was discarded.
The combined CH2Cl2 were returned in the separatory funnel and was washed with 20 ml 6M NaOH solution. The NaOH was discarded. The CH2Cl2 layer was drained into a clean, dry flask containing half spatula of anhydrous Na2SO4. The Na2SO4 was swirled and allowed to settle. The concentrated CH2Cl2 was extracted to dryness over a boiling water bath. Purification, the crude caffeine was transferred in a filter tube with a fitted inner test tube serving as “cold finger” and into hot air bath for at least 35 mins. The group constantly refill the cold finger with ice water.
After the 35th minute, the inner tube was removed and the caffeine clinging in the cold finger was removed and weighted into Aluminium foil. The crystalline caffeine characterization, the caffeine crystals were grind and mixed by mortar and pestle into a very fine powder. 2 microtube were used for the caffeine crystals and standard caffeine (1) and standard caffeine only. Both micro capillary tubes were sealed at one end. The pulverized caffeine crystal was scooped using the open end of the mircotube. The height of both sample were 3mm.
The crystals were packed well at the bottom of the tube by letting it fall inside a 1-meter long glass tubing and letting it bounce up and down tabletop. The melting point determination using a Thiele tube, the microtubes were fastened at the sided of the thermometer using rubber bands. The thermometer was clamped and the Thiele tube was dipped in cooking oil. The Bunsen burner was placed at the bottom of the beaker with cooking oil. The temperature range between the first appearance of the liquid within the sample to the disappearance of the last traces of solids.
Appendix 1. Weight of the vial + caffeine = 17. 6856 g Weight of the vial = 17. 6813 g Weight of the caffeine = 0. 0043 g 2. % yield=pure caffeinetea leaves mass x 100 0. 07% =0. 0043 g6. 4448 g x 100 References [1] (n. d. ). Retrieved July 13, 2011, fromhttp://spot. pcc. edu/~chandy/241/CaffeineExtractionCH2CCl2. pdf [2] (n. d. ). Retrieved July 13, 2011, from http://en. wikipedia. org/wiki/Caffeine [3]Murray, S. D. , & Hansen, P. J. (1995). The Extraction of Caffeine from Tea. Journal of Chemical Education , 851-852.
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