Экстракция кофеина из чая

Выделение природного алкалоида методом жидкостной экстракции

Organic Synthesis Advanced (University) 90 мин ~$15,00

Цель

Извлечь кофеин из чайных листьев жидкостной экстракцией дихлорметаном, показав принципы экстракции растворителем и выделения природных продуктов.

Предпосылки

Tea contains 2-4% caffeine by dry weight. After brewing a concentrated tea, caffeine is extracted into dichloromethane (DCM), which is immiscible with water. Sodium carbonate is added to convert tannins to sodium salts, keeping them in the aqueous layer while caffeine partitions into DCM.

Предупреждения по безопасности

DCM is a volatile organic solvent — work in fume hood
DCM is denser than water (lower layer in separating funnel)
Avoid inhaling DCM vapors
Do not use open flames near DCM

Требуемые СИЗ

goggles gloves lab_coat

Материалы

Tea bags (black tea) (4 bags)
Strong black tea
Dichloromethane (DCM) (60 mL)
Extraction solvent
Sodium carbonate (Na₂CO₃) (5 g)
To deprotonate tannins
Anhydrous sodium sulfate (5 g)
Drying agent
Hot water (200 mL)
Freshly boiled

Оборудование

250 mL beaker Separating funnel Ring stand Evaporating dish Hot plate Buchner funnel

Процедура

Brew a strong tea by steeping 4 tea bags in 200 mL of hot water for 10 minutes. Squeeze out the bags and allow to cool.

15 мин

Add 5 g Na₂CO₃ to the tea. Stir until dissolved.

3 мин

Transfer the tea to the separating funnel. Add 20 mL DCM. Shake gently with frequent venting.

5 мин DCM pressure — vent often

Allow the layers to separate. Drain the lower DCM layer into a clean flask.

3 мин DCM is the lower layer

Repeat the DCM extraction two more times with fresh 20 mL portions. Combine all DCM extracts.

10 мин

Dry the combined DCM extracts over anhydrous Na₂SO₄ for 10 minutes. Filter.

12 мин

Carefully evaporate the DCM in a fume hood using a warm water bath (not a hot plate directly). White caffeine crystals should remain.

15 мин Fume hood essential — DCM vapors

Weigh the crude caffeine. Calculate the yield per gram of tea.

5 мин

Ожидаемые результаты

White to off-white crystalline caffeine, typically 20-50 mg from 4 tea bags. The crystals should have a bitter taste. If a melting point apparatus is available, pure caffeine melts at 235-238°C.

Уборка

Evaporate remaining DCM in fume hood before disposing of waste. Rinse glassware with acetone then water. Dispose of DCM waste in halogenated solvent container.

Детали

Категория: Organic Synthesis
Сложность: Advanced (University)
Продолжительность: 90 мин
Прим. стоимость: $15,00
Шаги: 8
Материалы: 5

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Frequently Asked Questions

What is the objective of Экстракция кофеина из чая?

How difficult is Экстракция кофеина из чая?

This experiment is rated as Advanced (University). It takes approximately 90 minutes to complete.

What safety precautions are needed for Экстракция кофеина из чая?

Key safety precautions include: DCM is a volatile organic solvent — work in fume hood; DCM is denser than water (lower layer in separating funnel); Avoid inhaling DCM vapors.

What materials are needed for Экстракция кофеина из чая?

The main materials required are: Tea bags (black tea), Dichloromethane (DCM), Sodium carbonate (Na₂CO₃), Anhydrous sodium sulfate, Hot water.

What results should I expect from Экстракция кофеина из чая?