Jaybee Balilea, Sharmaine Baysic, and Maria Anjelette Patricia Belen 3BIO7, Department of Biology, University of Santo Tomas, Manila, Philippines
Extraction is a technique for isolating and purifying organic substances. In this technique, a solution is combined thoroughly with a second solvent that is immiscible with the first solvent. The solute is extracted from one solvent into the other because it is more soluble in the second solvent than in the first.
In this experiment, there were two types of extraction used and these were the Liquid-liquid extraction and Solid-liquid extraction. Liquid-liquid extraction involves a liquid solvent to remove a liquid component from liquid while Solid-liquid extraction allows soluble components to be removed from solids using a solvent. These two types of extraction were used to extract caffeine from tea leaves (Thea sinensis). Caffeine belongs to the group of compounds known as Alkaloids. Alkaloids are a diverse group of compounds that are found in plants and contain basic nitrogen atoms.
There were three methods used in extracting caffeine from tea leaves. These were isolation, purification and characterization of caffeine. Based on the calculations made and with the use of these three methods, a caffeine percentage of .05% and melting point range of standard caffeine and purified caffeine, 27°C and 20°C, respectively were obtained.
Extraction is a separation technique that involves selectively removing one or more components of a solid, liquid, or a gaseous mixture into a separate phase . The substance being extracted is separated between two immiscible combined phases, and the ratios of its distribution between the phases depend on the relative solubility of the solute in each phase.
A type of extraction, Liquid-liquid extraction is a process used in isolating and purifying products from chemical reactions. This technique includes distributing a solute between two immiscible liquids. The immiscible liquids normally encountered in the organic laboratory are water and some organic solvent. This process can be considered a competition between two immiscible liquids for the distribution of solute. Another type of extraction used in this experiment is Solid-liquid extraction. This is a process of removing soluble components from solids using solvent.
Caffeine is a natural product belongs to the group of compounds called Alkaloids  . It stimulates respiration, the heart and the central nervous system, is a smooth muscle relaxant and a diuretic. In the experiment, tea leaves were use to extract caffeine. Usually in tea leaves there are 30 to 75 mg per cup caffeine.
This experiment aims to isolate, to purify, to characterize caffeine from tea leaves and to calculate the percentage yield of caffeine from tea leaves.
Results and Discussion
The experiment was divided into three parts: isolation, purification and characterization. In isolation part, Lipton yellow label tea leaves were used. And these was pre-weighed and extracted in boiling 100 ml distilled water for 5 minutes. Boiling water was used so that tea leaves swell to release caffeine and other compounds such as tannins. Then the extract in a flask were cooled with use of running tap water and it was transferred in a separatory funnel containing 20ml of CH2Cl2. Dichloromethane was used to selectively extract the caffeine from the water which retains most of the other organic compounds. In this experiment, solubility is the principle behind extraction. The separatory funnel was shook gently to make sure that the solvent moves along the tea leaf particles to extract all the caffeine. The stopcock of the separatory funnel was opened while shaking to release any pressure building up inside. After shaking, the CH2Cl2 lower layer was drained into a clean flask and this shaking and draining was repeated 3 times until...