Chemistry Project to Determine the Caffeine in Tea Samples
Determination of Caffeine in Tea Samples
Name: Ankit Bahuguna Class: XII-A
Acknowledgements
First of all I would like to thank my cousin brother Mr. Neeraj Naithani, Research Scholar, Department of Chemistry, IIT Roorkee, for his contribution in this study. I would also like to thank my Chemistry Teacher Ms. Rampal for providing a helping hand in making this project titled “Determination of Caffeine in Tea Samples”.
Disclaimers: The errors, idiocies and inconsistencies remain my own.
Certificate
It is hereby certified that the original and genuine research work is carried out to investigate about the subject matter and the related data collection, and has been completed solely and satisfactorily by this student regarding the project titled “Determination of Caffeine in Tea Samples”.
Introduction
Tea is the most commonly and widely used soft beverage in the household. It acts as a stimulant for the central nervous system and skeletal muscles. That is why tea removes fatigue, tiredness and headache. It also increases the capacity of thinking. It is also used for lowering body temperature. The principal constituent of tea, which is responsible for all these properties, is the alkaloid caffeine. The amount of caffeine in tea leaves varies from sample to sample.
Originally it was thought that caffeine is responsible for the taste and flavour of tea. But pure caffeine has been found to be a tasteless white substance. Therefore, the taste and flavour of tea is due to some other substance present in it. There is little doubt that the popularity of the xanthene beverages depends on their stimulant action, although most people are unaware of any stimulation. The degree to which an individual is stimulated by a given amount of caffeine varies from individual to individual.
For example, some people boast their ability to drink several cups of coffee in the evening and yet sleep soundly; on the other hand there are people who are so sensitive to caffeine that even a single cup of coffee will cause a response bordering on the toxic.
The xanthene beverages also create a medical problem. They are dietary stimulants of the CNS. Often physicians face the question whether to deny caffeine-containing beverages to patients or not. In fact, children are more susceptible than adults to excitation by xanthenes.
For this reason, tea and coffee should be excluded from their diet. Even cocoa is of doubtful value. It has a high tannin content - may be as high as 50 mg per cup.
After all, our main stress is on the presence of caffeine in xanthene beverages and so in this project we will study and observe the quantity of caffeine varying in different samples of tea leaves.
Theory
The most important methylated alkaloid that occurs naturally is caffeine. Its molecular formula is C8H10N4O2. Its IUPAC name is 1,3,7-trimethylxanthene and its common name is 1-methylated theobromine.
Purely it is a white, crystalline solid in the form of needles. Its melting point is 123°C. It is the main active principle component of tea leaves. It is present in tea leaves up to 3% and can be extracted by first boiling the tea leaves with water, which dissolves many glycoside compounds in addition to caffeine. The clear solution is then treated with lead acetate to precipitate the glycoside compounds in the form of lead complex. The clear filtrate is then extracted with chloroform, which extracts caffeine because it is more soluble in it than water.
Uses of Caffeine
- In medicine, it is used to stimulate the central nervous system and to increase the flow of urine.
- Because of its stimulating effects, caffeine has been used to relieve fatigue. But it is dangerous and one may collapse if it is not consumed within a certain limit.
- Caffeine is also used in analgesic tablets, as it is believed to be a pain reliever. It is also beneficial in migraines.
Effects of Caffeine
- It is a psycho-stimulant.
- It improves physical and mental ability.
- Its effect on learning is doubtful but intellectual performance may improve where it has been used to reduce fatigue or boredom.
- When administered internally, it stimulates the heart and nervous system and also acts as a diuretic. On the contrary, excessive use is harmful to digestion and long-term use leads to mental retardation.
Procedure
- First of all, 50 grams of tea leaves were taken as a sample and 150 ml of water was added to it in a beaker.
- The beaker was heated up to extreme boiling.
- The solution was filtered and lead acetate was added to the filtrate, leading to the formation of a curdy brown coloured precipitate.
- Lead acetate was kept on being added until no more precipitate formed.
- The solution was filtered again.
- The filtrate so obtained was heated until it was reduced to 50 ml.
- The remaining solution was allowed to cool.
- After that, 20 ml of chloroform was added to it.
- Two layers appeared in the separating funnel.
- The lower layer was separated.
- The solution was then exposed to the atmosphere in order to allow the chloroform to evaporate.
- The residue left behind was caffeine.
- It was weighed and the observations were recorded.
A similar procedure was performed with different samples of tea leaves and the quantity of caffeine was observed in each.
Observations
1. Red Label Tea (Brooke Bond)
| Measurement | Value |
|---|---|
| Weight of china dish | 46.60 gms |
| Weight of china dish with precipitate | 47.20 gms |
| Amount of caffeine | 0.60 gms |
2. Yellow Label Tea (Lipton)
| Measurement | Value |
|---|---|
| Weight of china dish | 46.60 gms |
| Weight of china dish with precipitate | 47.15 gms |
| Amount of caffeine | 0.55 gms |
3. Green Label Tea (Lipton)
| Measurement | Value |
|---|---|
| Weight of china dish | 46.60 gms |
| Weight of china dish with precipitate | 47.05 gms |
| Amount of caffeine | 0.45 gms |
Result
- Quantity of caffeine in Red Label tea is 60 mg per sample of 50 gm.
- Quantity of caffeine in Yellow Label tea is 55 mg per sample of 50 gm.
- Quantity of caffeine in Green Label tea is 45 mg per sample of 50 gm.
Graph: Bar graph comparing caffeine content (mg) across Red Label, Yellow Label, and Green Label tea samples (plotted from data above).
Order of quantities of caffeine in different samples of tea leaves:
Red Label > Yellow Label > Green Label