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Extraction of Crude Caffeine from Tea using Liquid-Liquid Extraction
INTRODUCTION Extraction of Crude Caffeine from Tea using Liquid-Liquid Extraction
Alkaloids, such as caffeine, are often physiologically active in humans and are known central nervous system stimulants and diuretics (Wang, 2011 ). Acidic tannins, undecomposed chlorophyll, cellulose and pigments are also found in tea leaves. In order to extract caffeine from tea leaves, caffeine must be present as the free base (Amrita, 2013 ). In order to do so,a difference in solubility must occur to separate the tannins into the aqueous layer. Sodium carbonate is added to the extraction medium to ensure that the acidic components in the tea leaves remain water soluble and that caffeine is the free base.
Objectives:
Safety Precautions:
Materials and Apparatus: EXPERIMENT 5: Extraction of Crude Caffeine from Tea using Liquid- Liquid Extraction (3) Black tea bags (^) (1) 200-mL beaker (2) Erlenmeyer flask (4) 20-mL test tubes with cap (5) 20-mL test tubes (3) 50-mL beakers
Materials and Apparatus: EXPERIMENT 5: Extraction of Crude Caffeine from Tea using Liquid- Liquid Extraction Sodium Carbonate Distilled water Set-up of Organic Solvents
Procedures: EXPERIMENT 5: Extraction of Crude Caffeine from Tea using Liquid- Liquid Extraction In an isolated beaker, stir 20 mL of distilled water and 2 g of sodium carbonate until the Na 2 CO 3 dissolves and boil. Remove the beaker from heat, remove the boiling stick, and add the tea bag. Squeeze out as much water from the tea bag using string of the bag or glass rod for support. STEP 1 STEP 2 STEP 3
Add 6 mL of either diethyl ether, hexane, or chloroform to the test tube, and cover the tube with clean cork or rubber stopper. Shake the tube tightly several times. Between 1 - 2 seconds, open the tube to let excess pressure release from the tube. SINGLE MULTIPLE Determine which layer is the organic layer by performing a drop test. Add a drop of solvent or water to mixture. 2 x STEP 6 STEP 7 STEP 8
SINGLE MULTIPLE CaCl Solvent CaCl
Add a wooden boiling stick and evaporate the solvent using a warm water bath at around 70 °C. Determine the yield of caffeine. SINGLE MULTIPLE Compare the yield from the two extractions. STEP 12 STEP 13 STEP 14
Results and Discussion: EXPERIMENT 5: Extraction of Crude Caffeine from Tea using Liquid- Liquid Extraction Physical Appearance of Crude Caffeine: Powdery white Amount of caffeine extracted using diethyl ether. One extraction: 3.1mg Multiple Extraction: 18.2 mg Amount of caffeine extracted using hexane. One extraction: 0 mg Multiple Extraction: 9.331 mg Amount of caffeine extracted using chloroform. One extraction: 389 mg Multiple Extraction: 3064.9 mg