Extraction Of Caffeine From Tea Leaves Analysis Essay Example

would be better. After that, the side of the beaker was cooled in running tap water for two minutes. An ice cube might also help to cool more the sample. The tea extract was transferred in a separatory funnel containing 20 mL of dichloromethane/DCM/methylene chloride and the caffeine was extracted. The pressure inside was released constantly. The extraction of DCM lower layer was drained twice into a clean flask. All DCM portions were combined. The H2O layer was discarded. A 20 mL 6M NaOH solution was also used to wash the caffeine and must be discarded also. A half spatula of anhydrous Sodium sulfate (Na2SO4) was used to drain DCM layer which must be transferred in a clean, dry flask. Sodium sulfate was swirled and was allowed to settle. The DCM extract was concentrated to dryness over a boiling water bath. The weight of solid was recorded.

For the purification process, the crude caffeine was transferred in a filter tube with a filted inner test tube serving as “cold finger” and into a hot air bath for at least 35 minutes. Col finger was constantly refilled with ice water. The caffeine was scraped off in the cold finger and into a weighed Aluminum foil. The % yield was calculated. For the summary of the procedure, here is a clearer presentation of the sequence of steps:

• Results and Discussion
• Experimental Proper Pure Caffeine was extracted and purified by means of solvent extraction and sublimation.

Firstly, solvent extraction was done with the use of Methylene chloride/ Dichloromethane/ DCM as extracting solvent. DCM is an organic compound. It is a colorless, volatile liquid. It is not miscible with water but

it is miscible with many organic solvents. Thus, it has been commonly used to decaffeinate coffee and tea. Sodium hydroxide solution was also used to wash away further impurities in the decaffeination of the tea. Another compound, anhydrous sodium sulfate, was mixed to the extracts. Sodium sulfate is a white crystalline solid used as a drying agent.

The sodium sulfate removes any water and water soluble salts that are retained in the dichloromethane or accidentally transferred during decantation. Solvent extraction is a method used to separate compounds based on their relative solubilities in two different immiscible liquids. It is an extraction of a substance from one liquid phase into another liquid phase. It is a basic technique in chemical laboratories, where it is performed using a separatory funnel. Some solutes can be extracted from one phase to another without the need for a chemical reaction.

This is the simplest type of solvent extraction. When a solvent is extracted, two immiscible liquids are shaken together. The more polar solutes dissolve preferentially in the more polar solvent, and the less polar solutes in the less polar solvent. [3] All these extracting solvents and desiccant were carried out to assure that pure caffeine will be obtained from the process. For the purification process, sublimation was done. A cold finger is a piece of laboratory equipment that is used to generate a localized cold surface.

It is named for its resemblance to a finger as is a type of cold trap. Typically, a cold finger is used in a sublimation apparatus. Sublimation is the process of transition of a substance from the solid phase to the gas phase without passing through an

intermediate liquid phase. [4] After extraction and purification, a white, glistening needle-like pure caffeine was obtained. B. Calculations As seen in the Table 1 below, there is a great difference between the weights of the crude and pure caffeine. The former got 0. 0580 g while the latter got 0. 092 only, having a 0. 0488 difference. The very small accumulation of caffeine may be the cause of little time of heating the cold finger. Also, the group suspects that the boiling of the tea leaves in the first part of the experiment may also be one of the causes. The boiling tea bags might have less squeezed out or not that boiled well, resulting to little caffeine content.

A. Extraction Brand of Tea Leaves Lipton Yellow Label Tea Weight of Tea Leaves6. 44 g Volume of CH2Cl260. 0 mL B. Purification Weight of Crude Caffeine0. 0580 g

Physical Characteristics of crude caffeineYellowish, powdery form Weight of Empty Vial27. 0952 g Weight of Pure Caffeine + Vial27. 1084 g Weight of Pure Caffeine 0.0092 Physical Characteristics of pure caffeineWhite crystals/glistening needles % caffeine0. 143 % Table 1. Results from the Experiment

Conclusion

Caffeine from tea leaves was extracted by means of solvent extraction with the separatory funnel containing DCM, 6M NaOH solution, and anhydrous Na2 SO4 solution that are mixed with the extract sequentially. It was then purified with the use of cork-fitted tube as the cold finger.

Pure caffeine has the characteristics of odorless, white, fleecy masses, glistening needles or powder. The calculated % yield (% caffeine) was 0. 143%.

References

1. http://www. oxford. net/~mavarod/portal/school/caffeine. html
2. http://www. scienceteacherprogram. org/chemistry/Paul00-2. html
3. Chang, Raymund. (2011). General Chemistry: The essential concepts, 6th Ed. McGraw-
   

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