Extraction of caffeine in tea (sublimation method)

. Summary of experiments:Understand and master how to purify solid products using sublimation methods, understand the principles and methods of extracting caffeine from tea, and learn how to separate purified useful ingredients from natural products, master the principles of sublimation and its operation.principle:
caffeine has the effect of stimulating the heart, excited brain nerves and diuretic, mainly used as central nerve excitation drugs. It is also part of a group of drugs such as A.P.C. The modern pharmaceutical industry uses synthetic methods to make caffeine.
coffee because of the derivatives of radon, its chemical name is 1,3,7-tri-methyl-2, 6-hydrogen dioxide, its structure is similar to the tea base, cocoa base.
pure coffee because of white needle-like crystals, odorless, bitter taste, soluble in water, ethanol, chloroform, acetone, slightly soluble in petroleum ether, insoluble in benzene and ether. It is a weak alkaline substance, and the aqueous solution reacts neutrally
the
test paper of the stone. Caffeine loses crystalline water at 100 degrees C and begins sublimation, which is significant at 120 degrees C and rapidly at 178 degrees C. The melting point of a waterless caffeine is 234.5 degrees C.
tea contains a variety of alkaloids, the main components are about 1 to 5% caffeine content, and contains a small amount of soy and cocoa base, as well as 11 to 12% tannin acid (also known as tannic acid), as well as about 0.6% pigment, cellulose and
protein
and so on.
in order to extract caffeine from tea leaves, the appropriate solvents (e.g. chloroform, ethanol, benzene, etc.) are often used to extract continuously in fat extractors, and then the solvent is steamed out, i.e. coarse caffeine. Crude caffeine also contains alkaloids and impurities that can be further purified using sublimation.
extraction: an operation in which a substance is used to achieve separation, extraction or purification by means of differences in solubility or distribution ratio between two insoluble solvents.
sublimation: it is one of the
to
solids and organic compounds. Some substances have a fairly high vapor pressure in the solid state, when the
heats
without entering the liquid and directly vaporized, the vapor meets the next condensation into a solid, a process called sublimation. Sublimation products have a high purity, this method is particularly suitable for purification of moisture-prone solutions or with solvent decomposition of substances.
sublimation is a method of purifying solid organic matter. Sublimation allows the removal of hard-to-volatile impurities or the separation of solid mixtures with varying volatility. Sublimation can often obtain a higher purity product, but the operation time is long, the loss is also larger.
experiment used direct sublimation to extract caffeine from tea.
direct sublimation method is to break the tea in the container directly heated to 110 degrees C to 160 degrees C, caffeine sublimation, after cooling, collection and crystallization, to obtain pure products.main
reagents
:raw lime powdermain equipment: 1. evaporative dish
2. Alcohol lamp
3. tripod
4. Glass rod
5. scale
6. asbestos mesh
7.
. Filter paper 8. Cotton
9. Research
10. ResearchExperimental material:
teaexperimental steps: 1. 10g tea, 3.5g raw lime mixed into powder, placed in an evaporative dish on the alcohol lamp small fire roasted to light yellow, so that all water removed.
2. After cooling, the powder on the side of the evaporative dish is wiped off with filter paper to avoid contamination of the product when sublimation.
3. Cover the evaporative dish with a piece of filter paper with many small holes (with a pin), then cover the appropriate size glass
flepper
on top, the neck of the funnel stuffed with a little cotton, reducing vapor escape.
4. Sublimation is heated by a small fire of alcohol lamps on asbestos networks. The resulting vapor
through
small holes in the filter paper, which are cooled and condensed on the filter paper holes or funnel walls. When white hairy crystals are observed on the paper holes, stop heating and let them cool themselves, if necessary, the outer wall of the funnel can be cooled with a damp cloth. When steam is not available in the funnel, the funnel and filter paper can be unwraveled, and caffeine attached to the paper and around the vessel can be carefully scraped and collected. Weigh and calculate yield.Notes:
Life Sciences Experimental Technology Forum 1. In addition to absorbing water, the role of raw lime can also neutrally remove some acidic impurities (such as niacin), mixed into raw lime to be uniform, grinding to be carefully and well-balanced.
2. The key to this experiment is sublimation, sublimation process to control the temperature. Be sure to heat a small fire, slowly heat up, preferably the tip of the flame of the alcohol lamp just touch the asbestos net, slowly heat 10-15 minutes. If the flame is too large and heats up too quickly, both the filter paper and caffeine will be carbonized and blackened, making the product yellow (decomposed). If the flame is too small and heats up too slowly, it will waste time, and some of the caffeine has not yet sublimation, affecting the yield.
3. When scraping off caffeine, be careful to prevent mixing with impurities..