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Isolation of Caffeine from Tea Leaves

Isolation of Caffeine from Tea Leaves. Caffeine. Alkaloid Purine Ring System Stimulant (50 – 200 mg) Diuretic. Caffeine. Found in natural sources Coffee Tea Kola nuts Cocoa beans. Tea. Caffeine 5% by weight Soluble in hot water Tannins High MW phenolic compounds Soluble in water

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Isolation of Caffeine from Tea Leaves

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  1. Isolation of Caffeine from Tea Leaves

  2. Caffeine • Alkaloid • Purine Ring System • Stimulant (50 – 200 mg) • Diuretic

  3. Caffeine • Found in natural sources • Coffee • Tea • Kola nuts • Cocoa beans

  4. Tea • Caffeine • 5% by weight • Soluble in hot water • Tannins • High MW phenolic compounds • Soluble in water • Cellulose • Insoluble in water • Other substances • Chlorophyll, etc…

  5. Isolation Procedure Hot water CH2Cl2 Na2CO3 Heat

  6. Isolation Procedure Open two tea bags and weigh contents to the nearest 0.0001g. Record weight. Put tea into one bag, close, and staple.

  7. Isolation Procedure • Add … • 50 mL of distilled water (not 30 mL) • 2.0 g anhydrous Na2CO3 • Heat (gentle boil) for 20 min • Cover with watch glass and hold down, if necessary, with glass rod. • DO NOT BREAK THE BAG!!

  8. Isolation Procedure • Decant the hot liquid into a 50mL beaker (not erlenmeyer flask) • Wash with 10 mL hot water (instructor has hot water) • Add wash water to extract • Cool to room temperature!! • Discard tea bags in waste container

  9. Isolation Procedure • Transfer the tea extract to a separatory funnel on a ring clamp

  10. Isolation Procedure Carefully add 5.0 mL of dichloromethane (DCM) to the separatory funnel. Follow the procedure in the lab manual CAREFULLY (pg. 89 step 5). Your instructor will now demonstrate the proper extraction procedure using the separatory funnel!

  11. Isolation Procedure • You MUST be individually checked off by your instructor (after pre-lab lecture) before you can complete this step during lab!

  12. Isolation Procedure • Make sure … • the stopper is held tightly and no liquid spills • The liquid is not in contact with the stopcock when you… • …open the stopcock to release built up pressure caused by gas accumulation • Then close the stopcock and gentlymix by inverting funnel. • Release the pressure as before! • Gently mix and vent 2 – 3 times

  13. Isolation Procedure • Return separatory funnel to the ring clamp • REMOVE the stopper • Two distinct layers will form after a few minutes What is in the top layer? The bottom layer??

  14. Isolation Procedure • CAREFULLY drain the lower layer into a 25mL erlenmeyer flask • Try not to get any water into the flask!

  15. Isolation Procedure • Repeat the entire extraction procedure with an additional 5 mL DCM. then … • Combine the separated bottom layer with the DCM layer obtained previously

  16. Isolation Procedure • Add 0.5 g anhydrous Na2SO4 to remove excess water • No swirling necessary!

  17. Isolation Procedure • Weigh a small beaker (30mL) or separatory funnel containing 1 – 2 new boiling stones! • By means of gravity filtration, filter the DCM – salt mixture • Rinse with an additional 2 ml DCM

  18. Isolation Procedure • Remove the DCM by evaporation in the hood • Use a hot water bath • Monitor carefully – do not leave your hood! • Be careful not to overheat! • DCM is toxic – do not breathe fumes • While the DCM is evaporating, clean up your station • Follow lab procedure to calculate percent yield!

  19. Melting Point Determination • Dispose of all waste in hazardous waste containers • Then… your instructor will show you how to determine the m.p. of your caffeine! 

  20. Caution! • Dichloromethame • Toxic and must be carefully handled • It evaporates quickly – do not get excess! • Do not waste!! • You must be checked off on the separatory funnel procedure prior to the extraction step

  21. Potential Health Concerns • Inhalation: irritant, allergen, coughing, drowsiness, damage to the lungs, shortness of breath, labored breathing, loss of appetite and delayed lung edema • Ingestion: corrosive, burning, headaches, gastritis, intoxication, blindness, pain of the mouth and stomach, anorexia, thirst, diarrhea, dizziness, nausea, vomiting, irritability, confusion, low blood pressure, tachycardia, tachypnia, mental disturbances, skin discoloration, circulatory collapse, clammy skin, weak pulse, shallow respirations, coma and death • Skin contact: irritant, delayed burns, redness, cracking, flaking, dermatitis, defatting of the skin, absorption through the skin and white and wrinkled skin later • Eye contact: irritant, corrosion of the eyes with burns, tearing, redness, pain, blurred vision, permanent damage and blindness • Tumorigen, mutagen, teratogen and reproductive effector

  22. Finally … • This was the last lab!   • Next week - Be prepared for the cumulative written final! • Goggles • Lab coat • Pencil • Calculator • Eat before class! • Wear yellow! 

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