Extraction of Caffeine  

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  1. Slide 1 (Gavin)
    Good Morning everyone! We are group 6 from project 3 and we will be presenting about the extraction of caffeine from tea bags. I’m Gavin...

    What is caffeine? (SLIDE 2)
    Caffeine is an example of a type of organic weak base called alkaloid. Caffeine is a stimulant and is found naturally in tea, coffee and cola nuts.

    Positive and negative effects of caffeine (SLIDE 3)
    The positive effects of caffeine is that it keeps you awake and alert when you are tired.

    The negative effects of caffeine is that it causes headaches and hallucinations. Deaths may even occur due to over-dosage.

    Process (SLIDE 4)
    The process of extracting caffeine from the tea bags consists of four main stages. Boiling, filtration, solvent extraction and rotary evaporation.

    Boiling (SLIDE 5)
    For boiling, 10g of calcium carbonate and 25g of tea bags is added to 250ml of boiling water. Hot water is used instead of cold water, as the caffeine in the tea bags is more soluble in hot water and will dissolve faster. Calcium carbonate is added to convert the tannin, a substance in the tea bag which is also soluble in water, into a non soluble form in the organic solvent (dichloromethane) so that only caffeine can be extracted from the filtrate. During the boiling process, we also have to stir the solution to ensure homogeneous mixing.

    Filtration (SLIDE 8)
    Büchner Filtration is used to filter out the calcium carbonate and some other solid tea substances. The filtrate obtained will mainly be the caffeine and tannins and the residue will be the calcium carbonate and some other solid residues. the filtrate was then left to cool to room temperature. Vacuum is created so that the filtrate has space to flow into the flask and to ensure efficient filtration.

    Solvent Extraction (SLIDE 11)
    For solvent extraction, we will need to add 50ml of dichloromethane to the filtrate in the separating funnel and swirl it around a few times before extracting the organic layer which has a higher density (bottom layer) and contains caffeine dissolved in dichloromethane. After extracting the caffeine from the aqueous layer, magnesium sulphate is added to absorb any residual water from the organic layer. After that, we will need to filter the magnesium sulphate out from the organic layer, leaving only caffeine dissolved in dichloromethane which is collected in a round bottom flask.

    The round bottomed flask will then be connected to the rotary evaporator. A rotary evaporator is a device used in chemistry labs for the efficient and gentle removal of solvents from samples by boiling. A reduced pressure is applied to allow boiling at a lower temperature. The rotary evaporator will remove the dichloromethane in the organic layer and solid caffeine is obtained as an end product.

    The picture on the left is a rotary evaporator as mentioned previously. The things in the red tray are all the apparatuses that is required for this experiment. The picture at the bottom is our end product. It is solid caffeine which is in the form of a white powder.

    We will want to thank all the teachers who have been involved with the setting up of this educational camp, for giving us the chance to be involved in such meaningful work. We also want to thank the Professor, Dr Alessandra Bonanni for guiding us through this project and the Teaching Assistants, Weslie, Jeremy, Jonathan, Shumin and Adeline for being of a great help to our group. Thank you.