Isolation of Caffeine from Tea Leaves using Multiple Liquid-Liquid Extraction

Topics: Liquid-liquid extraction, Solubility, Water Pages: 5 (1346 words) Published: October 27, 2014
ABSTRACT

This study is about the isolation of caffeine from tea leaves in Lipton tea bags using the multiple extraction method. The objective of this study is to differentiate simple extraction from multiple extraction method and to obtain the percentage yield of caffeine for both extraction methods. Ten grams of tea leaves was boiled in a solution of 4.4 g of anhydrous sodium carbonate and 100 mL of distilled water. From this solution, caffeine was extracted using 60 mL of dichloromethane which was added in increments for about three times. The mixture of organic extract and a half a spatula of anhydrous sodium sulfatewas decanted to collect the residue in theseparatory funnel and evaporating it to dryness in a tared evaporating dish covered by a perforated filter paper so that everything except caffeine would evaporate under the hood. The percentage yield was computed by getting the ratio of the weight of caffeine and the weight of tea leaves used multiplied by a 100% which resulted to 0.8%.

Introduction
Extraction is a separation technique based on thedifferences in the solubility of substances in two immiscible solvents (usually water and a water insoluble organic solvent).1There are two main types of extraction methods performed inthe laboratory namely: the liquid-liquid extraction, which is also known aspartitioning or solvent extraction, which is also subdivided into two types, which are simple and multiple, and solid-liquid extraction. Liquid-liquid extraction is commonly used in organic chemistry. The liquid-liquid extraction has two types which are single extraction and multiple extraction. Single extraction involves using the whole solvent in the extraction process whilemultiple extraction involves repeated extraction process and each extraction introduces the solvent in increments. The method used in this study was multiple liquid- liquid extraction method. The objectives of this experiment were to extract caffeine from 10 g of tea leaves, to know the amount ofcaffeine present in the 10 g of tea leaves, to differentiatemultiple liquid- liquid extraction from simple liquid-liquidextraction method and to calculate the percentage yield of caffeine in 10 g of tea leaves using the assigned extractionmethod.

II. Methodology
Multiple liquid –liquid extraction method was assigned to odd-numbered groups and the simple liquid-liquid extraction method was assigned to even-numbered groups. 4.4 grams of anhydrous sodium carbonate was weighed by student no.5 and was placed in a small Erlenmeyer flaskand was dissolved in a pre-heated 100 mL distilled water bath. At the same time, 10 g of tea leaves contained in a tea bag was weighed in the triple beam balance by student no. 3. It was then dipped into the heated mixture by student no.4. After 10 minutes of boiling, the tea bags were emptied by student no.6 of its contents by using a glass rod and pressing it against the size of the flask to ensure that all of its contents will be removed. This procedure should be done carefully so as not to accidentally destroy the tea bags because it will prolong the experiment performed. The mixture wasallowed to cool for about 3 minutes before being transferred into the separatory funnel by student no.1. 60 mL of dichloromethane was introduced for three times and each timein increments during the extraction process by student no.2. The separatory funnel was turned upside down and the pressure inside the stopcock was released by opening it as shown in Figure 1. In mixing, the stopcock was swirled and was turned upside down to release the pressure inside. After mixing, the separatory funnel was placed in a steady position so that the mixture would settle so that the separation of the two layers would be clearly visible. An evaporating dish was measured in a triple beam balance by student no. 5 and a half a spatula of anhydrous sodium sulfate was introduced in the...

References: 1 California State University, Department of Chemistry (2005). Extractions. Retrieved from September 10,2014 from the California State University website: http://chemistry.csudh.edu/faculty/noel/CHE317L/Extraction%20Experiment.htm.
2 Bathan, G., Bayquen, A. et al (2014). Laboratory Manual in Organic Chemistry Revised Edition. Quezon City: C&E Publishing,Inc.
3 Landgrebe, J.A.(1993). Theory and Practice in the organic laboratory with microscale and standard scale experiments(4thed).Australia: Brooks/Cole.
4 Penn State University, Department of Chemistry (2003). Liquid-Liquid Extractions. Retrieved from September 10,2014 from the Penn State University website: http://courses.chem.psu.edu/chem36/Experiments/PDF%27s_for_techniques/Liquid_Liquid.pdf.
5 University of Colorado, Department of Chemistry (2006). Drying Organic Solutions. Retrieved from September 10,2014 from the University of Colorado website: http://orgchem.colorado.edu/Technique/Procedures/Drying/Drying.html.
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