Among the most addictive compounds that are consumed by man beverages form part, with coffee and tea being the most consumed and acceptable drinks. Tea powder “is a product obtained from the tea leaves, containing a small percentage of chlorophyll, tannins (acidic), and a very sensitive compound, caffeine, which is a stimulant” (Cabrera, 2008). The occurrence of caffeine in both coffee and tea has rendered these beverages the most popular addictive stimulants. As a matter of fact, in 30 grams of tea the prevalence of caffeine is approximately 0.07-0.37% (Cabrera, 2008).
This analysis has rendered tea a major contributor of caffeine in man relative to other beverages. Apart from stimulating the nerves, some other negative effects of caffeine on the consumer include insomnia, headache and nausea. With these facts, analysis on caffeine in tea forms an interesting subject to explore. Moreover, it is fascinating to know how this compound can be extracted from the leaves through the best possible way that would not interfere with the analysis. To this end, in this paper explores soxhlet extraction, a method billed to be the best.
Soxhlet method is arguably the best method to be used in the extraction of compounds in tea (Xuejun, 2003). This method does not result in chemical modification of the compound in question since it does not subject the material to direct heat over a prolonged extraction period (Vivekananda, 2006). As a consequence, most of the organoleptic elements are maintained, and the quantitative analysis yields a near-perfect result since negligible quantity of the compound is lost (Campanella & Bonanni, 2003).
The principle employed “in this method is quite intricate than what meets the eye” (Zulema & Miguel, 2009). Caffeine, an alkaloid, is chemically referred to as 1, 3, 7-trimethylxathine. This compound is represented as below:
The numerous nitrogenous elements you see in its compound play a significant role in the caffeine’s physiological activities. The soxhlet extractor explores caffeine’s physiology to isolate it from a mixture of compounds in a process called extraction. With an appropriate solvent, caffeine is accurately selected from the mixture, ending up in the extract. In this method, dichloromethane, a solvent, is used to separate caffeine from its aqueous state.
This is owed to the fact that caffeine is relatively more soluble in it (140mg per ml at room temperature) than it is in H2O (22mg per ml). Given the fact that dichloromethane and water are immiscible liquids, the caffeine dissolved in dichloromethane is separated from water, and since water is less dense, the extract forms the lower layer in the separating funnel (Zulema & Miguel, 2009). Nevertheless, since water is slightly soluble in the solvent, anhydrous sodium sulfite is added to the extract to get rid of the residual water.
Caffeine has a melting point (M.P) of 238oC, and sublimates at a temperature range of between 120 and 170oC. As such, it can be purified quite easily by sublimation. Particularly, in an effort to establish the purity of the sample, one can check the melting point of the ensuing sample, or use Thin Liquid Chromatography (TLC) to compare the retention factor (Rf) of both the sample and the authentic caffeine (Vovk & Simonovska, 2005). The Rf is obtained from the equation:
- Rf = (distance moved by the sample)/ (distance moved by the authentic compound)
In a synopsis, caffeine in tea constitutes a very interesting subject since it is a drug that is understandably a stimulant. For the sake of analysis, soxhlet method is billed as the best method to explore since most of the elemental properties are held intact without chemical modifications. The purity of the extract can be determined by TLC or by determining the M.P of the compound (Wang & Scott, 2004).
References
Cabrera, C. (2008). Determination of Tea components with antioxidant activity. Journal of agricultural and food chemistry 51 (90), 4427-4435.
Campanella, L., & Bonanni, A. (2003). Determination of the antioxidant capacity of samples of different types of tea, or of beverages based on tea or other herbal products, using a superoxide dimutase biosensor. Journal of Pharmaceutical and Biomedical analysis 32 (13), 725-736.
Vivekananda, M. (2006). Microwave assisted extraction tool for medicinal plant research. Journal of PHCOG REV, 11 (9), 14-16.
Vovk, I., & Simonovska, B. (2005). Separation of eight selected flavan-3-ols on cellulose thin-layer chromatographic plates. Journal of Chromatography, 1077 (7), 188-194.
Wang, C., & Scott, M. (2004). Determination of catechins and catechin gallates in biological fluids by HPLC with colourimetric array detection and solid phase extraction. Analytica Chimica Acta, 510 (5), 69-76.
Xuejun, P. (2003). Microwave assisted extraction of tea polyphenols and tea caffeine from green tea leaves. Journal of Chemical engineering and processing 42 (17), 129-133.
Zulema, P., & Miguel, P. (2009). Determiantion of catechins by means of extraction with pressurized liquid. Journal of chromatography 1026 (45), 19-23.