Extraction of Caffeine from Tea Leaves

Topics: Liquid-liquid extraction, Caffeine, Solubility Pages: 7 (2197 words) Published: September 9, 2013
Extraction of caffeine from Lipton tea leaves

Maria Gianna Beatrice L. Cancio*, Joe Mari Isabella B. Caringal, Rowena A. Chiang, Patricia Deanne del Valle Department of Biological Sciences, College of Science, University of Santo Tomas, España, Manila, Philippines Abstract

Caffeine was extracted from Lipton tea leaves by multiple extraction techniques namely solid to liquid extraction and liquid to liquid extraction; the purification by sublimation and melting point determination. Three teabags with weight 6.2674g were boiled with water and then extracted with 60 mL DCM; extract was dehydrated with anhydride Na2SO4 then was collected by decanting to an evaporating dish where it was evaporated to dryness. Crude caffeine with a weight of 0.0446g gave out a 0.7116% yield; after sublimation, the sublimate weigh 0 .0009g with a percentage yield of 0.0144%. Melting point determination was the last step where the sublimate was compared to a standard caffeine, where both gave out the temperature range of 228 ̊C – 230 ̊C.

Introduction

Caffeine is a bitter substance found in coffee, tea, soft drinks, chocolate, kola nuts and certain medicines. It has many effects on the body’s metabolism, including stimulating the central nervous system. This can make one more alert and give a boost of energy. [1]

Most people have high tolerance for caffeine and this can be manifested with the cups of coffee one can consume in a day. However, too much caffeine intake can make one restless, anxious, uneasy, and irritable. It may also keep one from sleeping well and cause headaches, abnormal heart rhythms, or other problems. Age and body size can make a difference in effect. A child or a smaller person may feel caffeine’s effects more strongly than an adult or a heavier, taller person. [2]

Caffeine in tea leaves comprises about 5% of its weight.
Extraction is a very common laboratory procedure used when isolating or purifying a product. The principle of extraction depends on the concept of immiscibility between two phases to separate a solute from the other phase. Extraction of caffeine is basically the isolation and purification of caffeine from mixtures like that of tea leaves. Most common extractions in organic chemistry are solid-liquid, liquid-liquid and acid-bases. In this experiment, 2 of these extractions are used; first the solid-liquid, followed by the liquid-liquid extraction.

Solid-liquid extraction is an extraction process by which compounds that are dissolved or suspended in a liquid mixture are separated from other compounds in the mixture according to their physical and chemical properties. It allows soluble components to be removed from solids using a solvent. [3] In this case the soluble component is the caffeine; the solid, tea leaves and the solvent, water. It is afterwards followed by a liquid-liquid extraction.

Liquid-liquid extraction also known as Solvent extraction or Partitioning is a method to separate compounds based on their relative solubilities in two different immiscible liquids usually water and an organic solvent. It is an extraction of a substance from one liquid into another liquid phase. It is performed in a separatory funnel. In this case the water is the water with caffeine extraction and the organic solvent, DCM.

After the extraction steps, purification, the process of separating a substance of interest from foreign or contaminating elements called impurities; was necessary to produce from crude caffeine, a pure caffeine.

Sublimation is one of the purification processes. It is a physical change in which a solid sample is allowed to be converted to its vapour state directly without passing the liquid state. At a point where the vapour pressure equals the atmospheric pressure before melting stage is reached, a compound may vaporize directly without passing the liquid state. Compounds with high vapour pressure are good candidates to sublime under normal atmospheric pressure.

As a...


References: [1] retrieved from http://www.nlm.nih.gov/medlineplus/caffeine.html
[2] retrieved from www.nlm.nih.gov/medlineplus/druginfo/caffeinesystemic202105.html
[3] retrieved from http://www.gunt.de/download/extraction_english.pdf
[4] retrieved from http://www.polaris.nova.edu/~shanbhag/chemistry/oc1labs/caffeine.pdf
[5] retrieved from http://chem-courses.ucsd.edu/CoursePages/Uglabs/143A_Weizman/expt_3N.pdf
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