In this experiment, caffeine was extracted from tea leaves in boiled water, then via an
acid-base liquid-liquid extraction using an organic solvent (ethyl acetate). The organic layer is
then washed with a saturated solution of sodium carbonate to remove any acidic impurities and
dried with an inorganic drying agent (anhydrous magnesium sulfate). This was done in order to
remove any traces of water before the solvent was evaporated to leave crude caffeine. As a
result, the percentage caffeine isolated from the tea was 2.5%.
% caffeine isolated from tea = (weight of sample / weight of tea bag) x 100%
= (0.07g / 2.8g) x 100%
= 2.5%
The brand of tea used in this experiment was Tetley, and my product changed from a
coloured liquid (dark magenta) to a pure, white crystalline solid.
Since the weight of the sample that I obtained was 0.07g and resulted in a 2.5% of
caffeine isolated from tea, this falls between the ideal 2-5% by weight (g/ 100g). A low yield is
typically due to a loss of product, which can be caused by emulsion (formed via vigorous
mixing) or by neglecting a proper washing of the extract.