Isolation Of Caffiene From Tea Leaves Flashcards
What does the tea leaves consists of?
Cellulose (Water-insoluble polymer of glucose which is
considered the building material of the plants).
2- Caffeine (Water-soluble and has Basic properties)
3- Tannins (plant polyphenols and they have acidic properties).
•Tannins are colored phenolic compounds of high
molecular weight (500-3000) that have acidic properties
What is meant by extraction?
a separation method used to isolate (extract) the compounds mainly from their natural sources based on their solubility difference in two different immiscible liquids (Liquid-liquid extraction)
What are the conditions of The organic solvent used in the mixture?
1- Don’t react with each other
2- Immiscible (Don’t mix)
3- Have different density
4- very volatile
5- Non toxic, Non flammable and inexpensive
What is meant by the distribution coefficient, KD?
At a certain temperature, the ratio of concentrations of a solute in each solvent is always constant. KD= solute organic/ solute aq
Why should you break down the extract into smaller volumes but more extractions?
What is meant by emulsions and how to remove them?
Emulsion (cloudy appearance because it scatters the light that passes through it) is a mixture of two immiscible solvents in which one solvent dispersed in the other. making the two solvents very difficult to be separated.
There are many ways to prevent the formation of the emulsion or to break the emulsion in the extraction:
1- Use cold aqueous layer (wait for the first layer to cool down)
2- Mix gently
3- Release the build-up pressure inside the Separatory funnel
4- Break the emulsion with long stirring rod
5- Let the two solvents to settle down for a longer time
What are the steps in the extraction of caffeine from tea leaves?
1- In a beaker take 80.0 mL from the alkaline tea solution, ready prepared for you
2- divide your solution to two fractions, 40.0 mL each.
2- Using a separatory funnel extract once the first 40.0 mL with 20 mL DCM.
3- Separate the DCM fraction, dry with Na2SO4,evaporate solvent and weight your caffeine solid, record the mass as ml
3- Using a separatory funnel extract twice the second 40.0 mL with 10.0 mL DCM in each extraction
4- Separate the DCM fraction each time, combine both fractions and dry with Na2SO4,evaporate solvent and weight your caffeine solid again, record mass as m2.
