THE RAPID EXTRACTION OF CAFFEINE FROM
NoDoz TABLETS
A Purification by Recrystallization
Introduction:
Caffeine is a mild stimulant of the respiratory and nervous systems as well as a mild
diuretic. It is a relatively simple (see structure below) alkaloid. Alkaloids are nitrogencontaining compounds (usually amines) which exhibit physiological effects and are obtained
from plants. Many commonly used products contain caffeine: coffee, cola drinks, tea,
chocolate, pain relievers, cold remedies, diet pills, and “stay awake” pills (such as NoDoz) to
mention a few. Caffeine is one of the compounds that does not exist in the liquid state – it
sublimes. Of course it is water-soluble and so it is found in liquid solutions.
Recrystallization is a method of organic purification. Impure compounds can be purified
using this method provided a solvent can be found which will:
 Dissolve the compound while hot,
 Not dissolve the compound while cold, and
 Not dissolve the impurities at all, OR keep impurities in solution even when
cold
Luckily isopropyl alcohol is such a solvent for caffeine. When heated, the caffeine (along with
some of the impurities) in the NoDoz tablet will dissolve. When cooled, the caffeine comes out
of solution or “recrystallizes”. Any other impurities which were soluble in the hot solvent will
stay in solution in the cold solvent as well.
There are basically four steps involved in this recrystallization experiment.
1.
2.
3.
4.
Purpose:
Dissolving the caffeine in a NoDoz tablet in hot isopropyl alcohol,
Using gravity filtration to filter out the impurities which did not dissolve,
Recrystallizing the caffeine by cooling the solvent, and
Using gravity filtration a second time to filter out the caffeine from any other
impurities in the cold solvent.
To extract a pure form of caffeine from an over-the-counter drug such as NoDoz
Materials/Equipment:
Van Provides:
Microwave oven
Analytical balance
Mel-temp
Capillary tubes for Mel-temp
Mortar and pestle
heat-resistant gloves
isopropyl alcohol (2-propanol)
filter paper
NoDoz tablets
Teacher Provides:
1-250 mL beaker
1-100 mL beaker
1-10 mL graduated cylinder
Safety Considerations:



Always wear goggles and an apron in the laboratory.
Use heat-resistant gloves to handle the beaker from the microwave oven after heating.
Remember that cool glass and hot glass look the same!
Isopropyl alcohol is a flammable liquid. Watch the heating process carefully and DO NOT
OVERHEAT!!!
Procedure:
Part 1: Dissolving the Caffeine
1. Obtain one NoDoz tablet from your teacher and weigh it on an analytical balance. Record
the mass in the Data Table.
2. Use a mortar and pestle to grind the tablet into a fine powder.
3. Transfer the powder to a 250 mL beaker being very careful not to spill any.
4. Measure 10 mL of isopropyl alcohol (2-propanol) using a 10 mL graduated cylinder. Use the
alcohol to rinse all of the powder residue from the mortar and pestle into the 250 mL beaker.
Add small increments of alcohol to the mortar and gently swirl, then pour into the beaker.
Doing this three (3) times will insure complete (quantitative) transfer of all of the tablet.
5. Place the beaker and contents in a microwave oven. Press 2 0 0 to set the timer for 2
minutes. Press the POWER LEVEL button and then press 1. This will set the microwave to
a 10% power level. Press the START button. Carefully observe the beaker as it heats to
insure that the contents do not boil. DO NOT LEAVE IT UNATTENDED! Isopropyl
alcohol is a flammable liquid so DO NOT OVERHEAT!
Part 2: First Filtration
6. Properly fold a piece of filter paper and place in a short stem funnel. Place the funnel atop a
100 mL beaker. With proper care (and heat resistant gloves) remove the 250 mL beaker
from the microwave oven and carefully pour the contents onto the filter paper.
7. Add another 10 mL of isopropyl alcohol to the 250 mL beaker (the one used previously) and
swirl the beaker to rinse any residue from the sides. Heat this beaker a second time following
the instructions given in Step 5.
8. With proper care, remove the beaker from the microwave and pour the contents onto the
same filter paper used in Step 6 above. Dispose of the used filter paper in the garbage.
Part 3: Recrystallization
9. The extracted caffeine is now present in solution in the filtrate which is in the 100 mL
beaker. Allow this beaker to cool to room temperature. You may be able to see caffeine
crystals begin to form.
10. To maximize recrystallization, once the beaker has reached room temperature place it in an
ice bath being careful not to get any water or ice into the beaker. Scratching the inside of the
beaker with a glass stirring rod may increase or speed the recrystal-lization process also.
Your teacher will demonstrate this process.
11. While you are performing Step 10, place a small amount (about 25 mL) of isopropyl alcohol
in a beaker and place it in the ice bath also. This chilled alcohol will be used later to rinse all
of the caffeine crystals onto the filter paper (Step 13).
Part 4: Second Filtration
12. Obtain a second piece of filter paper and use a PENCIL ONLY to label it with your name or
lab group number and period. Once it is labeled, use the analytical balance to find the mass
of the filter paper and record it in the Data Table.
13. Properly fold this piece of filter paper and place in a funnel. Place this funnel atop the 250
mL beaker previously used (but be sure to clean it first). Pour the contents of the 100 mL
beaker into the filter paper. Rinse the beaker twice with chilled isopropyl alcohol (see Step
11), and pour the liquid into the filter paper. This will insure that all caffeine crystals are
transferred onto the filter paper.
14. Once the filtration is complete, discard the filtrate and leave the filter paper in the funnel
resting atop the beaker until the next day. DO NOT attempt to hurry the drying process by
heating in any way. Caffeine will sublime when heated.
15. After drying the caffeine crystals in the filter paper, find the mass of the filter paper and
caffeine using an analytical balance (the same one used to mass the filter paper in Step 11).
16. Use a Mel-temp apparatus to determine the melting point of the crystals. To save time, set
the Mel-temp to “7” until it reaches 210oC, then turn it down to “5”. The temperature may
drop at first, but will stabilize and then rise. The melting point will occur above 210oC.
17. When finished, the filter paper can be discarded in the trash. All glassware should be left
clean and dry. Capillary tubes used for melting point determinations should be discarded in a
broken glass container since they can tear through the plastic garbage liners.
THE RAPID EXTRACTION OF CAFFEINE FROM
NoDoz TABLETS
A Purification by Recrystallization
Data Table
Name(s): _______________________________
Lab Group/Period: ____________
_________________________________
Date: ________________________
Data Table:
Mass of one NoDoz Tablet
G
Mass of filter paper
G
Mass of filter paper + caffeine
G
Mass of caffeine extracted
G
Melting point of product
o
C
Calculations:
1. Calculate the percent caffeine composition for your NoDoz Tablet.
2. According to the product label each NoDoz Tablet contains 200 mg of caffeine. Using this
as the theoretical yield, calculate the percent yield for this recrystallization process.
3. Use the product label amount to calculate a percent error for your experiment.
4. The melting range of caffeine is 234-236oC. Calculate a percent error for your product.
Questions:
1. What were some sources of error for this experiment? How could they be improved?
2. Propose some changes to this procedure that could improve the percent yield of caffeine.
3. Why is the Melting Point of a substance an important property to observe?
4. Why is it recommended to use the same balance for measuring all masses?