Honors Chemistry II
THE EXTRACTION OF CAFFEINE FROM TEA
Purpose:
The purpose of this laboratory exercise is to successfully extract caffeine from tea
leaves using simple organic extraction techniques.
Discussion:
Answer the following questions to develop a discussion:
1. What are some example drugs that are found in natural sources?
2. Where is caffeine found?
3. In general, how is caffeine isolated from other compounds found in the natural
source?
4. Draw the structure of caffeine and the major component of tea leaves.
5. How does a centrifuge work? How will it be useful in this lab?
Objectives:
In this lab, you will...
1. extract caffeine from tea leaves.
2. calculate the percent of caffeine in a tea bag.
Materials:
50, 100, 400 mL Beakers
10 mL Graduated Cylinder
2 5 mL Centrifuge Tubes
Small Test Tube w/ cork stopper
Stirring Rod
Analytical Balance
Beaker Tongs
Crucible Tongs
Hot Plate
Centrifuge
Plastic Pipet
1 Tea Bag – string and tag removed
1 M Na2CO3
Aluminum Foil (10 cm X 10 cm)
Ethyl Acetate
Na2SO4
Sand
Ice
Scoopula
Safety Goggles
Paper Towels
Safety:



Wear safety goggles at all times.
No open flame is to be used in organic lab. Many organic compounds are
flammable.
Balance the centrifuge carefully. An unbalanced centrifuge can cause serious
harm to an individual.
Procedure:
Part 1: Tea Extraction
1. Find and record the mass of a tea bag with tea. Record the mass of an empty
tea bag from the chalkboard.
2. Place 10 mL of a 1 M Na2CO3 solution in a 50 mL beaker. Place the beaker
on a hot plate.
- Pinch the top of the bag with a 10 cm x 10 cm piece of Al foil. Put the
bag into the solution, but wrap the Al foil around the top of the beaker.
This will keep the bag off of the bottom of the beaker.
- Poke a small hole in the Al foil to allow steam to escape, and to add
distilled water to the solution as needed to maintain the 10 mL level.
- Boil for 5 minutes. DO NOT ALLOW IT TO BOIL OVER.
3. Carefully remove the beaker from hot plate using crucible tongs. Allow to air
cool for a few minutes, then cool to room temperature quickly using an ice
bath. Remove the foil and the bag. Squeeze out excess fluid from tea bag
with crucible tongs being careful not to break the bag. Discard the tea bag.
You should have no more than 8 mL of solution. If you have more, boil off
more water to concentrate the solution.
- If you need to boil longer, make sure the outside of the 50 mL beaker
is dry before placing it on the hot plate. Be sure to cool the extract to
room temperature in ice bath.
Part 2: Ethyl Acetate Extraction
4. Add 3 mL of ethyl acetate to the solution. Gently swirl the beaker for ~30
seconds.
5. Add half of the solution to a 5 mL centrifuge tube, and the other half to a
second 5 mL centrifuge tube. Make sure the volumes are exactly equal.
- Balance the centrifuge by putting the tubes in opposite holes.
- Centrifuge the mixture for 4 minutes.
6. Remove tubes from centrifuge. Using a plastic pipet, carefully remove the
clear upper layer of liquid. Squeeze the bulb of the pipet before putting the tip
of the pipet into the liquid. Put the tip all the way to the bottom of the clear
layer and release the bulb slowly. This will be a mixture of caffeine and ethyl
acetate. Place this liquid into a small test tube. Remove as much of the clear
layer as possible.
7. Pour the dark layer back into the beaker. Repeat steps 4 – 7 without cleaning
the centrifuge tubes or the beaker. After each extraction, be sure to pipet the
clear top layer into your test tube.
8. After the third extraction, discard the lower dark layer down the sink with
plenty of water.
Part 3: “Drying” and Evaporating the Ethyl Acetate/Caffeine Mixture
9. Add a small amount (1/2 pea-sized) of Na2SO4 to your test tube. Gently tap
the side of the test tube. The crystals will clump. Continue to add small
amounts of crystals to the test tube until the addition of new crystals does not
produce more clumping, or until you cannot add any more to the test tube.
10. Using the stirring rod, decant the fluid portion of your test tube into a 100 mL
beaker by carefully pouring the fluid along the stirring rod. Avoid getting any
crystals of Na2SO4 into the beaker.
11. After the decanting process is completed, the ethyl acetate must be carefully
and slowly evaporated leaving only the crude caffeine behind. Turn the hot
plate on medium high. Hold the 100 mL beaker a few centimeters above the
surface of the hot plate and swirl the mixture in the beaker. Do not let it boil.
The solid crude caffeine will remain in the beaker.
Part 4: Caffeine Sublimation
12. Assemble a sublimation apparatus as follows:
- Clean and dry (inside and out) a 50 mL beaker. Record its mass.
- Place the 50 mL beaker inside the 100 mL beaker containing your
crude caffeine. This is your sublimation apparatus.
13. Place the sublimation apparatus on a hot plate and begin heating on medium
heat. Fill the small beaker with chips of ice. Do not let ice or water fall into
the larger beaker.
14. Continue heating until the sublimation process is complete (all the crude
caffeine is off of the outer beaker). When heated, the pure caffeine will
sublime and deposit on the outside of the 50 mL beaker. Carefully observe
the sublimation process occurring between the 50 and 100 mL beakers.
15. Remove the apparatus from the hot plate with beaker tongs and allow to cool.
Remove the inner beaker very cautiously and carefully pour off the ice water
making certain no water comes in contact with the sublimed caffeine crystals.
16. Dry the inside of the 50 mL beaker using a paper towel. Record the mass of
the beaker with the caffeine on the bottom. Scrape the product from the
beaker into a small test tube and cork it. Keep the caffeine for the TLC lab.
Cleanup:
 Discard the tea bags in the trash.
 Rinse the used sodium sulfate down the drain with plenty of tap water.
 Clean all glassware with soapy water, rinsing three times with tap water and
three times with distilled water. Return used equipment to its proper location.
Calculations:
 Calculate the mass of tea in the tea bag.
 Calculate the mass of caffeine obtained.
 Calculate the percent of caffeine in one tea bag.
 Include percent yield, absolute and percent error calculations knowing that the
theoretical mass of caffeine in one tea bag is 55 mg.