Summary of Procedure:
This is an established liquid-liquid extraction application experiment.
Extraction of caffeine from tea, coffee, cola, and cocoa has been done thousands of times in ungraduate experiments.
Positive aspects of this experiment:
+ Many students are interested and concerned about caffeine so this experiment makes a nice connection with them.
+ Sublimation is an interesting technique.
Neutral (may be positive or negative) aspects of this experiment:
± Dichloromethane is preferred to ethyl acetate or TBME because it can be removed easily from the separatory funnel.
± In my experience a 250 mL separatory funnel is helpful to do the experiment on a scale where students obtain enough caffeine to see.
± In my folder, I have emulsion-busting strategies - what to do when students shake the tea too hard.
Negative aspects of this experiment:
- The yield of caffeine is quite small. This can be disappointing to students.
- The experiment consumes a large quantity of dichloromethane.
Inquiry & Extension Ideas:
● Many different types of teas and caffeinated beverages can be explored.
● What are the impurities? Can theobromine be detected?
Data Links:
caffeine from tea_UV
caffeine_from tea HPLC
Student Comments:
Student_Comments_2008_Tea
Photo Gallery:
The Schretzman Chronicles
2008 Student Handout: caffeine from tea
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