Extraction Of Caffeine Lab Template (Page 4 of 8) in pdf

Extraction of Caffeine

Procedure

1. CAUTION: It is best not to get dichloromethane on your skin. You may choose to wear

gloves during this experiment. Otherwise, wash thoroughly if you do get some on your hands.

CAUTION: Gas will build up in the separatory funnel while you are shaking it, so you must vent

the funnel occasionally to prevent the stopper from popping out, causing a mess and possibly

getting dichloromethane on your skin.

Obtain a separatory funnel and close the stopcock. Set up a ring stand on your lab bench to

support the “sep funnel.” Place 75 mL of coffee into the sep funnel. Add 20 mL of

dichloromethane and place the stopper in the top of the sep funnel. Shake the funnel for 1-2

minutes following the instructions given during the prelab lecture. Place the funnel back in the

ring stand and allow the two layers of liquid to separate—this may take a few minutes. The

lower layer will be dichloromethane. There may be an emulsion at the boundary between the

two layers—an emulsion is a region where “bubbles” of one liquid are suspended in the other

liquid, and the two refuse to separate. If an emulsion occurs, use a glass stirring rod to poke

around in the emulsion to break it up. Ask the instructor for help if the emulsion seems

particularly stubborn.

Be sure the stopper is removed from the top of the sep funnel for the following drainage step—

otherwise the liquid will drain out of the funnel extremely slowly. Once the two layers have

separated, or are nearly separated, drain the lower dichloromethane layer into a clean, DRY 250

mL flask. Be careful not to drain any of the COFFEE into the flask! It is best to leave a very

small amount of dichloromethane at the bottom of the sep funnel so as not to accidently allow

some coffee to escape.

The dichloromethane you just drained contains dissolved caffeine that has been extracted from

the coffee. However, it isn‟t possible to extract all the caffeine with a single portion of

dichloromethane. Therefore, you will do two more extractions using fresh portions of

dichloromethane in order to extract the majority of the caffeine that is in the coffee.

2. Set the flask containing the first portion of dichloromethane aside. Add a fresh 20 mL portion

of dichloromethane to the coffee in the sep funnel. Shake the funnel for 1-2 minutes. Allow the

two layers to separate again. Then drain the lower dichloromethane layer into the 250 mL flask

that already contains the first portion of dichloromethane—be sure to leave a very small

amount of dichloromethane in the funnel and don’t allow any coffee to drain out! At this

point the two portions of dichloromethane are together in the flask.

3. Repeat step 2. At the end of this step, the flask will contain all three portions of

dichloromethane. If everything went well, most of the caffeine from the coffee should be

dissolved in this solvent.

Extraction Of Caffeine Lab Template Page 4