Extraction of Crude Caffeine from Tea using Liquid-Liquid Extraction (PPT), Slides of Organic Chemistry

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EXPERIMENT 5

Extraction of Crude Caffeine from Tea using Liquid-Liquid Extraction

CHEM LAB1A GRP 4

INTRODUCTION Extraction of Crude Caffeine from Tea using Liquid-Liquid Extraction

CHEM LAB1A GRP 4

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:

1. Isolate crude caffeine from brewed tea by liquid-liquid extraction using hexane and diethyl ether extracting solvents.
2. Compare the extraction efficiency of the two extraction solvents.
3. Compare the extraction efficiency of crude caffeine by single and multiple extraction.

Safety Precautions:

1. Organic solvents are very volatile, toxic, and flammable. Review your material safety data sheets carefully before handling.
2. Work in a well ventilated area when handling solvents.
3. Do not work with organic solvents near an open flame.

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

• Layer
  • Layer - Layer
    • Layer

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

As most processes involved are physical processes, this type

of separation usually does not feature a chemical reaction

to explain the product.

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