Extraction of Caffeine

Experiment no. 3

Extraction of Caffeine from Tea Leaves

Dalangin, Yonnalyn

Desierto, Tricia*

Diaz, Luis

Estella, Karhen

Department Biological Sciences,

College of Science, University of Santo Tomas

Espana St. Manila 1008

Group no. 5 2MB

Date submitted: December 13, 2012

Abstract

The experiment shows the process in which a natural product undergoes extraction. Extraction is a separation process, uses two immiscible phases to separate a solute from one phase to another. In this experiment the tea leaves a natural product was used to extract the caffeine to identify the organic compound. Doing the process of isolation and purification, the physical properties of the organic compound will be identified. To characterize the purity of the sample, determination of melting point was performed. Purity is described when the sample is containing a single substance.

Introduction

Caffeine is known to act as a stimulant drug to the brain and the nervous system. It gives the body extra energy and makes a person more alert. It is present in most of the food products such as, chocolate, soft drinks, energy drinks, coffee and tea. However, excessive intake of caffeine makes your body restless, and may not help your body to function well. Although caffeine is safe to consume in moderate amounts, it is not recommended for children. It may have a negative effect on the child's nutrition. Caffeine is commonly found in leaves and plant fruits and naturally occurs in tea. On average, tea leaves contain 3% of caffeine.

This experiment illustrates the separation of a naturally occurring organic compound from the tea leaves using the process of extraction. Caffeine falls under the group of alkaloids, these are chemicals made from plants and consist of nitrogen organic compounds. There are two main types of extraction, the Liquid-liquid extraction which is divided into two types, the Single and Multiple extractions and the Solid-liquid extraction.

Methodology

In a 250 mL beaker, five weighed Lipton tea bags were placed in 100 mL of water. The beaker was covered and was boiled for 5 minutes to easily dissolve the caffeine. After boiling, the excess liquid in the tea bag was squeeze by pressing it with a stirring rod then it was cooled by adding 2 pieces of ice cubes. The extract was transferred in a separatory funnel containing 20 mL of CH2Cl2 that was added. To release the pressure inside the separatory funnel, it was turned upside down and the stopcock was opened. The separatory funnel was swirled to mix the solution, turned upside down to release again the pressure. This procedure was done for three to four times until two layers are visible. The aqueous layer was discarded by opening the stopcock to let it drain, after discarding it, 20 mL of 6m NaOH was added to eliminate the tannins, another compound that is present in the caffeine and converting it into salts. The NaOH layer was discarded and the organic layer was transferred in a 100 mL beaker. One full spatula of anhydrous was added before letting it evaporate. It was covered with a piece of paper with holes, and then was kept in the locker until it dries. Using a spatula, the dried powder was scraped from the beaker then ethanol was added to remove excess powder that was stuck on the sides. Using a water bath setup, it was heated under a hot plate until the powder turns to liquid, and then the beaker was placed in a basin with ice cubes until it crystallized. For the purification of Crude caffeine, capillary tubes were closed at one end by heating it using a Bunsen burner, and then 0.5 cm of standard caffeine was placed in tube 1, the purified caffeine to tube 2. Letting it pass through the glass tubes for several times will prevent the occurrence of air space inside the capillary tube. It will slow down the melting process if air space is present in the substance, this will affect the convection process because the heat will first pass through the air spaces before it starts to melt, so it is important to let the capillary tube bounce inside the glass tube to prevent air space. After doing the capillary tubes, set up for melting point determination was fixed. A thermometer was immersed in a 100mL beaker with cooking oil. Two capillary tubes were attached on the sides of the thermometer to easily read the temperature, a Bunsen burner was used to heat the set up and determine the melting point.

Results and Discussion

Tea leaves 10.3596

Volume of CH2Cl2 20mL x 3 = 60 mL

Crude Caffeine Clear colorless liquid; after evaporation turns into crystallized powder

Pure Caffeine Physical characteristic - white powder

Melting point: 232oC - 234oC

Standard Caffeine Physical characteristic - white powder

Melting point: 230o C- 233oC

Caffeine

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