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Name: Mark John G. Girasol Date of Experiment: 20 Nov 2012

Groupmates: Stephanie O. Palacios

Denise Mae Q. Rosales

Date Submitted: 4 Dec 2012

Experiment No. 1

ISOLATION OF CAFFEINE FROM TEA

I. INTRODUCTION

Pure caffeine is a white, tasteless substance that makes up as much as 5% of the weight of

tea leaves. Structurally (as seen in the figure below), it is closely related to the purine bases,

guanine and adenine, found in deoxyribonucleic acids (DNA). Caffeine causes cardiac and

respiratory stimulation and has diuretic effects as well.

Several plants i.e., tea leaves, coffee beans, kola nuts, cocoa beans contain caffeine in

varying percentages. Cola soft drinks contain 14-25 mg of caffeine per 100 mL, and a sweet

chocolate bar weighing 20 g contains about 15 mg of caffeine. In tea however, the amount of

caffeine depends on the variety and where they are grown. Commonly, tea leaves contain about

3-5% caffeine by weight. Coffee, on the other hand contains only about 2%, yet a cup of it

Caffeine Purine


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contains 3.5 times as much caffeine as does a cup of tea. How does this happen? Coffee beans

are ground extremely fine while tea leaves are simply dried and directly added with water. As a

consequence, there is more ground coffee in one cup than does tea.

II. MATERIALS AND METHODS

6 bags Alokozay Black Tea (1 teabag 2.5g) 12.58 g sodium carbonate (Na2CO3) 30 mL chloroform (CHCl3) 1 pinch sodium sulphate (Na2SO4) 1 pinch sodium chloride (NaCl)

There were two parts of the experiment: the extraction and the distillation processes. The

first one was divided into solid-liquid and liquid-liquid extractions, the sequence of doing which

is in order.

In the solid-liquid extraction, six bags of Alokozay Black Tea weighing at about 2.5 g

were placed in a 400-mL beaker together with 12.58 g of Na2CO3 and some boiling chips. 175

mL of distilled water was added. The mixture was heated for 10 minutes. The liquid was

decanted to a 250-mL Erlenmeyer flask and was let cool to room temperature.

The second half of the extraction part was the liquid-liquid extraction. After the liquid in

the previous half was cooled, it was poured to a separatory funnel. It was added with 30 mL


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chloroform. It was gently shaken and the air that accumulated inside was released once in a

while. The clear chloroform layer was carefully collected in a 250-mL Erlenmeyer flask.

Addition of another 30 mL portion of chloroform was conducted. A pinch of Na2SO4 was added

to the pooled extract and then together, they were swirled gently. There was a remaining impure

chloroform layer filled with bubbles. A pinch of NaCl was added to it and then collected to the

same flask. Using a cotton ball as a filter, the extract was transferred to storage bottle.

The second part of experiment was the distillation process. Using the devised distillation

setup, the extract was distilled. It was also made sure at the same time that the temperature

should not exceed 60C. The distillate was collected in a beaker. The residue transferred in a

pre-weighed evaporating dish, which was not totally free of the distillate, was heated on a water

bath further drying it up until greenish crystals were seen. The evaporating dish together with the

crystals were cooled and weighed.

III. RESULTS AND DISCUSSION

Table showing the data gathered

Weight (g)

Tea bags 15

Evaporating dish 32.9504

Evaporating dish + caffeine crystals 33.1019

Caffeine yield 0.1515


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%caffeine yield =

100%

=0.1515 g

15 g 100%

= 1.01%

Chloroform was chosen to be the solvent because caffeine is soluble in it, and in itself is

immiscible in water, thus isolating caffeine from water-soluble impurities. It also has a lower

boiling temperature than caffeine, so it is easily distilled.

The idea of the extraction is to eliminate to hot water all water-soluble components and

impurities in tea that contribute to an additional mass of caffeine. This is to make caffeine as the

only one exclusively soluble to chloroform while the rest to water. Caffeine is readily soluble to

chloroform, but then, tannin, another component in tea, also is slightly soluble in chloroform.

We want to separate caffeine from the tannins by having the caffeine dissolved in

chloroform and the tannins in the water. The addition of Na2CO3 turns these tannins into salts

that do not dissolve and ionize in chloroform but in water and eventually becoming free from

caffeine. There is one practical disadvantage in converting the tannins to their saltsthey

become anionic surfactants. Surfactants cause water-insoluble substances to form emulsions with

water through adsorbing themselves to individual caffeine molecules, thus stabilizing the


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molecules. Emulsion is a suspension of one liquid to another. This is depicted by the bubbles

formed between the chloroform and aqueous layers. The chloroform-caffeine mixture should be

eliminated from the emulsion. The emulsified molecules formed are too small to be filtered.

Shaking of the separatory funnel increases the collisions of the molecules and thus coagulating

them. Another technique is adding NaCl, an ionic substance which is adhered to the adsorption

layer and sequentially attracting more emulsified molecules, thus, again, coagulating them.

Through these, bubbles were eliminated and a purer chloroform layer, free of tannin, was

extracted.

It should be noted, however, that when draining the extract, the stopper should be

removed. Otherwise, the stopper establishes a pressure inside the separatory funnel, so instead of

being drained, the extract remains inside. By removing the stopper, the pressure is released and

the liquid is free to flow.

The extraction should be done with two portions of chloroform because of its low

distribution coefficient (K25C = 8.36). If K


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The chloroform layer extracted is not 100% free of the aqueous portion. Traces of water

should be eliminated and the addition of Na2SO4 could do this for us. Water interferes with the

distillation process since water has a higher boiling temperature than chloroform, therefore, it is

not distilled.

The distillation process eliminates the chloroform through difference in volatility.

Chloroform has a lower boiling temperature (60C) than caffeine, so the chloroform was readily

distilled. The portion left in the distilling flask is the one that contains caffeine. It was further

heated until caffeine crystals showed.

IV. CONCLUSIONS

The method used in the isolation of caffeine from tea includes two parts: the extraction

and distillation. The extraction process is further divided into solid-liquid and liquid-liquid

extractions. In solid-liquid extraction, the other components of tea are eliminated using water as

the solvent. In the liquid-liquid extraction, chloroform was used to dissolve caffeine and to

separate it from water. Chloroform and caffeine are then subjected to distillation for separation

due to the difference in their boiling points. Since chloroform has lower boiling point, it

evaporated faster. The remaining liquid was then heated, thus evaporating the residual

chloroform and leaving the caffeine crystals.

The percent caffeine yield in Alokozay Black Tea is 1.01%.


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V. COMMENTS

The mass of tea used was 15 g instead of 20 g. This, as hypothesized, could contribute to

a greater negative constant error than if 20 g of tea was used. This is because if a portion of it

was spilled, the decrease in actual percentage is greater than if the same amount was spilled in

the latter condition, thus is less accurate.

The green pigmentations in the caffeine crystals were due to the dissolved chlorophyll.

Chlorophyll is also soluble in chloroform and since there was no measure conducted in order to

isolate it, it added to the yielded caffeine crystals. Same is true with some organic molecules that

might still be present together with the yielded caffeine.

VI. REFERENCES

Brown, T., LeMay, H.E., Bursten, B., Murphy, C., Woodward, P. Chemistry the Central Science

11th

Edition. Pearson Education, Inc.. 2009

Shanbhag. Caffeine Extraction. 2006. Retrieved from

http://www.polaris.nova.edu/~shanbhag/chemistry/oc1labs/caffeine.pdf

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