Which Food or Drink Delivers The Most Caffeine



Which Delivers The Most Caffeine?

Caffeine is a common stimulant found in a number of drinks, foods, and pills.

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Your task in this lab is to find the best source of caffeine. You will be provided with either Tea or No-Doze as a caffeine source and you will need to extract the caffeine from the substance you are given.

A procedure is given below (page 2).

Each group will take one of the materials given and try to extract as much caffeine as possible. You will of course need to identify that the substance you extract is indeed caffeine, and that it is pure. Then you will pool your results and make recommendations about which sources of caffeine you recommend. Your technique grade can be determined by the quality and quantity of caffeine isolated.

Before beginning, consult the “Scheme for Extraction of Caffeine from Tea” on the website.

Safety Precautions

Dichloromethane (methylene chloride) is toxic, irritating, absorbed through the skin and harmful if swallowed or inhaled. Use in a well ventilated hood, wear gloves and wash your hands thoroughly after handling it.

Caffeine is toxic and an irritant; avoid contact with skin, eyes, and clothing.

Techniques to learn/review

Extraction

Vacuum Filtration

Recrystallization

Melting Point Determination

Procedure for extraction of caffeine from tea and no-doze

1. Preparation of the aqueous caffeine solution

Take the source of caffeine (tea leaves) and weigh (accurately) about 10 g into a 250 mL beaker. (For the No-Doze grind up one tablet in a mortar and pestle (from the stockroom) and place it in the beaker.)

2. Add about 5g calcium carbonate and 100 mL water to the solid and boil the mixture for about 15 minutes on a hot plate - stirrer. (What do you think the calcium carbonate is for? Hint - it is a base)

3. Let the solution cool to about 50 (C (you DO NOT need a thermometer for this, 50 ˚C is warmer than room temp, but not too hot to the touch as to be unbearable) and filter using a Buchner funnel and vacuum filtration. Swirl; pour the mixture into the Buchner funnel so it is just one-half full. This may be a little messy but if the filter paper clogs up - just replace it and carry on with a new one.

4. Cool the filtered solution - you can use an ice bath to speed this up and then extract (separatory funnel from stockroom) it three times with 20 mL of dichloromethane.

5. Dry the combined extracts with anhydrous sodium sulfate (Na2SO4), filter off or decant the solution away from the drying agent and into a clean, dry, pre-weighed, 125 mL Erlenmeyer flask.

6. Clamp the Erlenmeyer flask containing the DCM on a steam bath, add a wooden stick to facilitate boiling and boil off the dichloromethane. Weigh the caffeine residue in the flask.

7. Recrystallize the caffeine from ethyl acetate (~5 mL of ethyl acetate). After the filtered caffeine has dried, weigh it and report that in your notebook. Compare your yield with others in your lab section. Record their results in your notebook also.

Waste disposal

Put the solid tea residue into the trash cans on the floor at the ends of the benches.

Pour the dichloromethane solutions into the chlorinated organic waste container.

Characterization of Caffeine

When you have obtained the caffeine check its purity by TLC, and characterize it by taking its melting point. An authentic sample is available.

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