Extraction of Caffeine from Tea and Coffee
Table of contents
iii
Table of contents
Contents
Table of contents ................................................................................. iii
Introduction ......................................................................................... v
Ch 1 ................................................................................................... 7
Set up ................................................................................................. 3
Materials .......................................................................................... 3
Time to make tea! ............................................................................. 3
Ch 2 ................................................................................................... 5
Extraction ............................................................................................ 7
Extracting the caffeine........................................................................ 7
Separating the emulsion ..................................................................... 8
Ch 3 ................................................................................................. 11
Sublimation ....................................................................................... 13
Set up ............................................................................................ 13
Begin the sublimation ....................................................................... 14
Introduction
Introduction
Extraction of a single component from a mixture of substances uses a
specific method that often exploits differences in acid-base properties and
the solubilities in two mutually immiscible solvents. Caffeine belongs to a
large class of compounds known as alkaloids. These are of plant origin,
contain basic nitrogen, often have a bitter taste and a complex structure,
and usually have physiological activity. Their names usually end in –ine;
many are quite familiar by name if not by chemical structure – for example,
nicotine, cocaine, morphine, and strychnine.
v
Ch 1
Chapter 1
3
Set up
Materials
Tea
30-mL beaker
Boiling stick
Hirsh funnel
Centrifuge tube
Ice
Sodium carbonate (anhydrous)
Dichloromethane
Anhydrous calcium chloride pellets
Erlenmeyer flask
25-mL filter flask
Scale
Sand bath
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Compounds
O
Boiling Point
178oC
851oC
1633oC
N
N
O
Melting point
238oC
N
N
Caffeine
sodium carbonate
Time to make tea!
Tea is easy to make, but in this procedure, we need to be very precise.
•
Place 15mL of water, 2g sodium carbonate, and a wooden boiling stick
in a 30mL beaker
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Bring the water to boil on a sand bath, which looks like the bottom half
of figure 1.
4
Extraction of Caffeine from Tea
Figure 1.
•
Remove the boiling stick and begin brewing a concentrated tea
solution by immersing the tea bag in hot water for 5 minutes.
•
Cool the tea bag and squeeze out as much water as possible
•
Bring the water to boil again, then add a new tea bag, repeating the
previous step.
Ch 2
Chapter 2
7
Extraction
Extracting the caffeine
Compound
Melting Point
Boiling Point
-96.7oC
39.6oC
Dichloromethane
•
Using three 2mL portions of dichloromethane, extract caffeine from
the tea
o Cork the centrifuge tube
o Shake gently

Shaking to hard will produce an intractable emulsion
•
An emulsion is a inseperable mixture of fluids that
don’t normally mix

Shaking to gently will fail to extract caffeine

You can break an emulsion by placing it in centrifugation
for 90 seconds
•
A centrifuge is shown below
8
Extraction of Caffeine from Tea
Separating the emulsion
•
After the extraction remove the lower aqueous layer into a reaction
tube
o The aqueous layer is the clear layer shown in the image above
•
Dry the extracts over anhydrous calcium chloride pellets for 5-10
minutes in an Erlenmeyer flask
o Add the drying agent in portions with shaking until it no longer
clumps together
•
Transfer the dry solution to a tared 25mL filter flask
o Wash the drying agent twice with 2mL portions of
dichloromethane
o Evaporate the contents of the flask to dryness
Chapter 2
9
o The residue will be crude caffeine

Determine the weight

We are not finished yet as we need to purify the crude
product by sublimation
Ch 3
Chapter 3
13
Sublimation
Set up
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Fit the filter flask with a pluro stopper through which is thrust a 15mL
centrifuge tube
•
Clamp the flask with a large three-prong clamp
•
Fill the centrifuge tube with ice and water
•
Heat the flask on a hot plate
14
Extraction of Caffeine from Tea
Begin the sublimation
•
Caffeine is reported to sublime at about 170oC
•
Use a heat gun to heat the upper walls of the flask
Chapter 3
•
When sublimation ceases, remove the ice water from the centrifuge
tube and allow the flask to cool to room temperature
•
Scrape the purified caffeine onto a receptacle
15