Extraction of Caffeine from Tea

Isolating a natural alkaloid using liquid-liquid extraction

Organic Synthesis Advanced (University) 90 min ~$15.00

Objective

Extract caffeine from tea leaves using liquid-liquid extraction with dichloromethane, demonstrating solvent extraction and natural product isolation.

Background

Tea contains 2-4% caffeine by dry weight. After brewing a concentrated tea, caffeine is extracted into dichloromethane (DCM), which is immiscible with water. Sodium carbonate is added to convert tannins to sodium salts, keeping them in the aqueous layer while caffeine partitions into DCM.

Safety Warnings

  • DCM is a volatile organic solvent — work in fume hood
  • DCM is denser than water (lower layer in separating funnel)
  • Avoid inhaling DCM vapors
  • Do not use open flames near DCM

Required PPE

goggles gloves lab_coat

Materials

  • Tea bags (black tea) (4 bags)
    Strong black tea
  • Dichloromethane (DCM) (60 mL)
    Extraction solvent
  • Sodium carbonate (Na₂CO₃) (5 g)
    To deprotonate tannins
  • Anhydrous sodium sulfate (5 g)
    Drying agent
  • Hot water (200 mL)
    Freshly boiled

Equipment

250 mL beaker Separating funnel Ring stand Evaporating dish Hot plate Buchner funnel

Procedure

1

Brew a strong tea by steeping 4 tea bags in 200 mL of hot water for 10 minutes. Squeeze out the bags and allow to cool.

15 min
2

Add 5 g Na₂CO₃ to the tea. Stir until dissolved.

3 min
3

Transfer the tea to the separating funnel. Add 20 mL DCM. Shake gently with frequent venting.

5 min DCM pressure — vent often
4

Allow the layers to separate. Drain the lower DCM layer into a clean flask.

3 min DCM is the lower layer
5

Repeat the DCM extraction two more times with fresh 20 mL portions. Combine all DCM extracts.

10 min
6

Dry the combined DCM extracts over anhydrous Na₂SO₄ for 10 minutes. Filter.

12 min
7

Carefully evaporate the DCM in a fume hood using a warm water bath (not a hot plate directly). White caffeine crystals should remain.

15 min Fume hood essential — DCM vapors
8

Weigh the crude caffeine. Calculate the yield per gram of tea.

5 min

Expected Results

White to off-white crystalline caffeine, typically 20-50 mg from 4 tea bags. The crystals should have a bitter taste. If a melting point apparatus is available, pure caffeine melts at 235-238°C.

Cleanup

Evaporate remaining DCM in fume hood before disposing of waste. Rinse glassware with acetone then water. Dispose of DCM waste in halogenated solvent container.

Details

Category
Organic Synthesis
Difficulty
Advanced (University)
Duration
90 min
Est. Cost
$15.00
Steps
8
Materials
5

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Frequently Asked Questions

What is the objective of Extraction of Caffeine from Tea?
Extract caffeine from tea leaves using liquid-liquid extraction with dichloromethane, demonstrating solvent extraction and natural product isolation.
How difficult is Extraction of Caffeine from Tea?
This experiment is rated as Advanced (University). It takes approximately 90 minutes to complete.
What safety precautions are needed for Extraction of Caffeine from Tea?
Key safety precautions include: DCM is a volatile organic solvent — work in fume hood; DCM is denser than water (lower layer in separating funnel); Avoid inhaling DCM vapors.
What materials are needed for Extraction of Caffeine from Tea?
The main materials required are: Tea bags (black tea), Dichloromethane (DCM), Sodium carbonate (Na₂CO₃), Anhydrous sodium sulfate, Hot water.
What results should I expect from Extraction of Caffeine from Tea?
White to off-white crystalline caffeine, typically 20-50 mg from 4 tea bags. The crystals should have a bitter taste. If a melting point apparatus is available, pure caffeine melts at 235-238°C.