Miina Härma Gymnasium

Which type of my family regular teas (black, green and rosehip)

has the highest level of caffeine in it?

Diana Toodo

Extended Essay

Chemistry

Word count: 3087

Tartu 2012

2

Table of Contents Table of Contents .................................................................................................................................... 2

Abstract ................................................................................................................................................... 3

Introduction ............................................................................................................................................. 4

Research question and hypothesis.......................................................................................................... 6

Effects of caffeine on human physiology and behaviour ........................................................................ 7

Procedure (method description) ............................................................................................................. 8

Results ................................................................................................................................................... 11

Analysis .................................................................................................................................................. 12

Conclusion ............................................................................................................................................. 15

Evaluation and limitations ..................................................................................................................... 16

Bibliography ........................................................................................................................................... 17

Appendix 1 ............................................................................................................................................. 18

Appendix 2 ............................................................................................................................................. 19

3

Abstract

This essay explores one research question, which is: Which type of my family regular teas

(aqueous solutions of black, green and rosehip tea) has the highest level of caffeine in it?

Three different sorts of tea are taken under observation in here. Caffeine is extracted by using

two solvents – initially (boiling) water and then chloroform (CHCl3).

Water with tea bags or smashed tea leaves is being boiled on a stove. The time water was

being boiled was 15 minutes. Tea is put into a separatory funnel along with chloroform.

Chloroform is used under fume hood – under proper ventilation and every precaution is being

used (proper gloves, masks and glasses). Since CHCl3 is a very intoxicating – those

precautions were necessary. After the extraction part was done – I had to prove, that the

substance I extracted was caffeine – for that I did TLC (Thin-Layer Chromatography) and

watched the results under UV-lamp (Caffeine absorbs UV-light and gives off visible light).

The maximum amount of caffeine was found in black tea, and the minimum amount was

found in rosehip tea, which was almost caffeine-free. It was also found that green tea has

quite big amount of caffeine in it – which for me was a surprise, since I thought that green tea

was supposed to be the natural tea, which does not have that much caffeine in it.

Word count: 224

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Introduction

Caffeine is a chemical called an alkaloid. Caffeine is a stimulant, that is most widely used in

the World. It is present in coffee, tea, chocolate and colas. It is legal and unregulated almost

everywhere, it is estimated, that in North America 90% of adults consume caffeine

daily.1Sometimes caffeine found in tea is also referred as theine.

Tea and coffee have been popular beverages for centuries now, primarily because they

contain caffeine. It stimulates respiration, the cardiac muscle, and the central nervous system,

and is a diuretic (promotes urination).2 Consuming caffeine in either small or large amounts

has different kinds of effects. Consuming it in small amounts enhances one’s mental energy,

it acts as diuretic, increasing the volume of urine; it can cause dehydration. Consuming

caffeine in high amounts can cause anxiety, irritability and insomnia, it can also cause

dependence (caffeinism, latin coffeinismus3 )– witch side effects are headaches and nausea.3

Then again caffeine is often included in the formulation of headache pills and other

medications1. Which brings me to a conclusion that small amount of caffeine is beneficial,

but too much is not beneficial. Effects of caffeine are dependent on people’s body weight, age

and the amount of caffeine they have daily.

Caffeine is found in plants – but why do plants produce caffeine? I found the answer to that –

caffeine paralyses and kills insects (caffeine acts as pesticide)2, which means that plants

protect themselves by producing caffeine.

Extraction is a process that can be used to determine the content of a certain substance within

a solution.4 There are several caffeine extraction techniques, and every one of them is

different from the other one (some of them are more difficult and, others are not so difficult

and duable in school terms).

1 C.Brown and M.Ford; Pearson Baccalaureate, Higher Level Chemistry developed specifically for the IB Diploma, 2009, p 642-43 2 http://tophqbooks.com/books/176032 3 Medicine Dictionary (finnish – ’’Lääketieteen termit’’), Medicina, 2004 4 http://www.oxford.net/~mavarod/portal/school/caffeine

5

As I said before, caffeine is an alkaloid, more exactly caffeine is called trimethylxanthine

(systematic name is 1,3,7-trimethylxanthine). The chemical is also known as coffeine, theine,

mateine (found in mate), guaranine (found in guarana)2, or methyltheobromine. Caffeine is

also soluble in water and in many organic compunds. Melting point of caffeine is 238°C and

sublimation point is 178°C. Caffeine is a white, odorless powder, but it does have a slightly

bitter taste5.

Fig. 16

The purpose of my experiment with caffeine is to find out which tea sort has the most caffeine

in it. I am interested in it, because everyone I know, who have done this experiment before,

have had different results – and so, I wanted to find it out myself – so I would know, which

tea I should drink, if I want to be more energetic for some time (I know that caffeine is not the

only stimulant in tea, but it is still the main stimulant). I chose to do the experiment with tea,

not coffee, because there are many people who even do not know that there is any caffeine in

tea.

For extracting caffeine I decided to use initially water and then chloroform for solvents – it is

the most simple method, I found – and it is doable at school terms, although for chloroform

some precautions have to be used (fume hood, gloves, a mask and glasses). The first solvent

that I use is water – I will make almost a regular tea (amount of tea will be a little bit bigger

so the caffeine amount would be also bigger). The second solvent, after the water is

chloroform, with a chemical formula CHCl3. Chloroform’s boiling point is at 61.15 – 61.70

°C14.

5 Edited by Gene A. Spiller, Ph.D, D.Sc., FACN; Health research and Studies Center and Sphera foundation, ’’Caffeine’’, Los Altos, California; CRC Press LLC, 1998 6 http://coffeaconsulting.com/assets/images/Caffeine%20molecule.png – Caffeine Molecule

As it is seen in the picture, caffeine contains heterocyclic rings (containing carbon and nitrogen) and a tertiary amine group. In addition caffeine contains two amide groups.1

6

Research question and hypothesis

My research question is : Which type of my family regular teas (black, green or rosehip) has

the highest level of caffeine in it? I chose this question due to my personal interest in the

subject. Since I had no idea, which tea sort has the highest caffeine – I deduced my hypothesis

from my own logic – I say that due to the fact that black tea, is the hardest sort of tea, it has

the highest level of caffeine in it and the lowest level of caffeine is in rosehip tea, because it is

a herbal tea. I chose 3 different sorts of tea – black tea, green tea and rosehip tea. I chose

those sorts, because these are the main sorts me and my family consume daily.

7

Effects of caffeine on human physiology and behaviour

By referring to human physiology, I mean how caffeine affects our organism’s functions (e.g

processes as nutrition, movement, and reproduction).7 Effects of caffeine depend on the

quantity of caffeine one consumes ( normal dose of caffeine usually does not have negative

effects, but has greatly positive effects on behaviour (exceptions are caffeine-sensitive

persons), while excessive dose may have great negative effects ).8 As the article referenced

above states, caffeine increases alertness and reduces fatigue; and increases anxiety in some

individuals. High doses of caffeine in the late evening will increase the time taken to go to

sleep (for some individuals) – but since some people are really at controlling their caffeine

intake, there is no strong evidence relating level of caffeine consumption to sleep problems.

Main effects on human physiology are increase in blood pressure by contracting the heart and

blood vessels in non-habitual users. Effects usually subside after three to four hours. Heavy

caffeine consumption raises (by about 2 mmol/L) the plasma levels of homocystine, which is

a risk factor for heart disease. Intakes of more than 5 cups per day have shown to raise

cholesterol levels by 0.5 – 1.0 mmol/L (20 – 40 mg/dL). Caffeine stimulates gastric secretion.

Some individuals are sensitive to caffeine and suffer ill effects such as acid indigestion,

heartburn, abdominal pain, gas or constipation. It increases urination (acts as diuretic). Liver

metabolism is affected by caffeine – it increases the level of cyclic AMP (adenosine

monophosphate) and decreases the level of branched chain and aromatic amino acids in

plasma. Caffeine consumption is also a risk factor for osteoporosis9, also tremor is a common

side effect on caffeine consumption. Caffeine in doses more that 3 cups per day can result in

male or female infertility. All of this paragraph was refered from the University of

Delaware’s Department of chemistry and biochemistry’s website10

7 http://www.medterms.com/script/main/art.asp?articlekey=8223 8 Article by A.Smith, ’’Effects of caffeine on human behavior’’, Center for Occupational and Health Psychology, School of Psychology, Cardiff University, UK, September 2002, published by Elsevier Ltd; http://intraspec.ca/Effects-of-caffeine-on-human-health.pdf, 1243,1244 and 1251 9 Medicine Dictionary (finnish – ’’Lääketieteen termit’’), Medicina, 2004, p 552 10 http://www.udel.edu/chem/C465/senior/fall00/Caffeine/Physiological.htm, ’’Physiological effects of caffeine’’

8

Procedure (method description)

Method description was mostly taken from chemistry lab called ’’Caffeine extraction from

tea’’ made by University of Pittsburgh at Bradford11, but it was altered a little – due to

absence of some devices at my school.

Table 1 – apparatus and chemicals

Apparatus for Part 1 Apparatus for part 2 Apparatus for part 3 Apparatus for

vertification of

caffeine

Large beaker (about

500 ml-s)

Chloroform Hot water bath TLC-plates

Tea bags or smashed tea

leaves (different sorts of

teas)12, Scale

Separatory funnel Stove/Gas burner Watch glass

Water Regular filter paper Scale Chloroform

Stirring rod

Stove/Gas burner

Decanting glass or a

flask

Decanting glass Decanting

glass

Stove, Timer Tripod Tripod Pencil, ruler

Regular filter papers

Hot pads

Oven gloves

Solution from part 1

Stirring rod

Solution from part 2 Caffeine

powder (from

part 3)

Erlenmeyer flask (125

ml), 100ml graduated

cylinder

Caffeine tablets Pipette

11 http://www.upb.pitt.edu/interior3Default.aspx?menu_id=42&id=7501 CHEM-023 Extraction of Caffeine in Tea 12 Black tea (Ahmad Tea London, Ceylon tea); Green tea (Pickwick, Pure green) and Rosehip tea (Lipton, Rosehip)

9

Method description

Part 1 of the experiment: Dissolution of caffeine in water

1. Obtain a beaker (500 to 1000ml)

2. Weigh tea bags or smashed tea leaves (about 10g) and place them in a beaker,

write down the actual weigh

3. Add 200ml of water to the beaker

4. Boil the water, which has tea bags in it, for about 10 to 15 minutes while stirring

occasionally (on a boiling point)

5. Cool the solution for about 15 minutes - You have to steep the tea for so long,

because then it will release more caffeine, as the caffeine content in tea depends on

the time the tea is steeped (especially in hot water)13

6. Squeeze tea bags of the liquid and dispose of the bags.

7. Using regular filtration, filter the solution through regular filter paper to remove any solid particles.

Part 2 of the experiment: Transfer of caffeine from water to chloroform

Chloroform has to be used under hood – do not breath in any fumes!

1. Transfer the solution obtained from the end of part 1 to a 500ml separatory

funnel, add 90ml of chloroform.

2. Allow the chloroform to settle to the bottom (wait for a few minutes). It settles to the bottom, because it is much denser in water and insoluble in it. Then, carefully drain the chloroform layer into a beaker (or a flask). Dispose of the aqueous top layer.

3. Filter the chloroform/caffeine solution through regular filter paper using regular filtration. This will allow the chloroform to filter through but will trap any residue. Transfer the solution to a 125ml flask (or a decanting glass).

13 http://www.thefragrantleaf.com/caffeine.html

10

Part 3 of the experiment: Crystallization of caffeine

1. Using a hot water bath in the fume hood, place the chloroform solution

over the boiling water. Boiling point of chloroform is 61.15 – 61.70 °C14

2. Evaporate the solution down to about 20ml and then remove from the heat. 3. Weigh a clean decanting glass and record its weight.

4. Place the decanting glass over the boiling water bath, fill it with a portion of the concentrated caffeine solution, and evaporate it. Repeat this process until all the concentrated solution is gone.

5. Remove the decanting glass from the water bath and let it cool. Wipe the moisture from the bottom of the decanting glass.

6. Reweigh the beaker and calculate the amount of caffeine.

Verification of Caffeine –using thin-layer chromatography and UV-lamp (ultraviolet

light lamp)

1. Take a little of the caffeine powder obtained from the previous experiment

and mix it with 10ml of chloroform

2. Put a few ml-s of chloroform in a small decanting glass

3. Take a TLC plate and mark a straight line (with a pencil) at the height of 1

cm, take a sample of caffeine-chloroform solutions with a pipette and place

a small spot on the TLC plate (at the height of 1 cm)

4. Place the TLC plate in a small beaker and cover it with a watch glass

5. Wait for about 10 minutes (meanwhile watch how the solvent travels up the

TLC plate)

6. To check if the substance you got from the last experiment is really

caffeine, UV-lamp is needed. Put the TLC-plate under the lamp and if the

substance shines, it is caffeine.

7. For further control TLC is carried out with caffeine tablets – if the solvent

travels up to the same height on TLC-plate, then the substance obtained

earlier (from part 3) is caffeine

14 http://www.general-anaesthesia.com/people/chloroform.htm

11

Results

Table 2 – data of results

Green Tea Black Tea Rose-hip Tea

Weight of tea

bags/smashed tea

leaves (in g-s,

uncertainty ±0,01g)

1. 11.06

2. 11.07

3. 11.06

1. 11.06

2. 11.06

3. 11.06

1. 11.07

2. 11.06

3. 11.06

Amount of water

used for brewing (in

ml-s, uncertainty ±

1ml)

1. 300

2. 300

3. 300

1. 300

2. 300

3. 300

1. 300

2. 300

3. 300

Amount of

chloroform used (in

ml-s, uncertainty ±

1ml)

1. 75

2. 75

3. 75

1. 75

2. 75

3. 75

1. 75

2. 75

3. 75

Amount of caffeine

received (in mg-s,

uncertainty ±10mg)

1. 140

2. 130

3. 140

1. 190

2. 200

3. 180

1. 40

2. 30

3. 30

Following observations were made during the experiments:

1) Tea was brewed for 15 minutes on a stove, then it was put on a table to cool down for

15 minutes also.

2) During the filtration a little of the tea must have got lost in a filter paper.

3) Tea was stirred with a stirring rod after every 3 minutes (5 times per one repetition)

12

Analysis

In black tea, there is in average 190 mg-s of caffeine, in green tea ≈ 137 mg-s and in rosehip

tea ≈ 33.3 mg-s.

In order to calculate how many times more caffeine is in one tea sort compared to another, I

have to do as follows: take the amount of caffeine in one sort of tea and divide it with the

amount of caffeine in the other sort of tea.

Example calculation:

Black tea vs green tea: 190 mg / 137 mg ≈ 1.4 (it means, that there is 1.4 times more caffeine

in black tea, than in green tea)

Relations between the caffeine amounts of different types of tea

Black Green Rosehip

Black 1 1.40 5.70

Green 0.70 1 4.10

Rosehip 0.18 0.24 1

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Graph

Relation between the amounts of caffeine in different types of tea

On the y-axis of

the graph, you can see the amount of caffeine in mg-s and on the y-axis, you can see the type

of tea

Verification of caffeine

Picture was taken, when TLC plates with 3 sorts of tea were under UV-lamps (from left to

right: TLC plates with caffeine extracted form green tea, black tea and rosehip tea). Caffeine

absorbs UV-light and gives off visible light. It is called fluoresence.15 Since all the substances

with multiple bonds glow under UV-lamp – further control was needed. TLC was conducted

with caffeine tablets (Cofi-Tabs; Vitabalans oy) to check if the solvent travels up to the same

height on TLC-plate as the solvent obtained from tea – and it did.

15 http://www.xula.edu/chemistry/documents/orgleclab/14Caff.pdf

0

20

40

60

80

100

120

140

160

180

200

Black tea Green tea Rosehip tea

14

The percentage of caffeine in tea

The equation for calculating the percentage of caffeine in tea is as follows15:

amount of caffeine recovered (g)

percentage of caffeine = ---------------------------------------- x 100%

weight of tea (g)

Percentage of caffeine in black tea (average value of caffeine in mg-s / average weight of tea

x 100%) = 0.19/11.06 x 100% = 1.72%

Percentage of caffeine in green tea = 0.136 / 11.063 x 100% = 1.22%

Percentage of caffeine in rosehip tea = 0.033/11.063 x 100% = 0.30%

15

Conclusion

Not very broad-based conclusions can be made, due to the fact that only 3 sorts of tea were

used (due to my personal connections – these are the tea sorts my family consumes daily).

Taking in consideration all the sources of errors, the experiment has gone successfully and the

hypothesis was right. I was actually quite surprised to find out that rosehip tea contains

caffeine at all, since it is said that it is caffeine free16. But maybe it is only in some brands and

mine happened to have caffeine in it.

From my results, it is seen that the highest level of caffeine from these three types is in black

tea, followed by green tea, and the lowest level of caffeine is in rosehip tea. However, to get

more accurate and reliable results, many improvements can be made ( which will be discussed

in the next chapter ). As it is seen on the picture provided above (on the page 13 ), the

substance on the TLC plates does glow under a UV-lamp – therefore I deduce, that it is

caffeine (although there was other stuff amongst caffein also, because there wasn’t a concrete

mark, there was an oval trace on the TLC plate). My calculations about how many times

more caffeine is in one sort than the other, show the following results: in black tea, there is

1.39 times more caffeine than in green tea, and 5.71 times more caffeine than in rosehip tea;

in green tea the amount of caffeine accounts for 72% of the amount, which is in black tea and

in green tea there is 4.11 times more caffeine than in rosehip tea and in rosehip tea, where is

the lowest level of caffeine, the amounts account for 18% (of the amount in black tea) and

24% (of the amount in green tea) respectively. Percentages of caffeine in tea are 1.72 , 1.24

and 0.30 from black to rosehip respectively. Also, the caffeine I extracted was not 100% pure

caffeine – the purest caffeine I got from black tea (it was really white, just as pure caffeine has

to be17), but in green tea, the caffeine powder was greenish, and in rosehip tea, it was a little

reddish – but it still contained mostly caffeine, because fluoresence occurred under UV-lamp.

16 http://ic.steadyhealth.com/health_benefits_of_rosehip_tea.html 17http://www.camh.ca/en/hospital/health_information/a_z_mental_health_and_addiction_information/caffeine/Pages/caffeine_dyk.aspx

16

Evaluation and limitations

Random errors could have occurred in the quantities of substances taken in use at the

beginning. Water and chloroform are subject to random error of ± 1ml from the measuring

cylinders and weight of tea bags/smashed tea leaves is a random error of ± 0,01g. As the

amounts of caffeine in one sort of tea varied for about 20 mg-s (0.02g) and not more, then it is

not a major source of concurrence – although in milligrams it seems a lot, it is actually only

0.02g (since the scale accuracy was 0.01g it is actually a really little concurrence).

In the first part of the experiment, after the tea was boiled and cooled down, the tea bags were

squeezed, which means that some of the liquid (which contains caffeine) remained behind in

the wet tea bag. This is the source of error, which is quite impossible to avoid (there is no

way that all the tea can be squeezed out of the tea bags). For more accurate results only tea

bags or only smashed tea leaves (these are preferable, due to the point written above) should

have been used. In my experiment with black tea, smashed tea leaves were used but with

green and rosehip tea, tea bags were used (which can be a source of error, because in smashed

tea leaves and tea bags – there might be different amounts of caffeine – this is one factor, that

should have been controlled, but was not).

Since chloroform has quite low boiling point (about 61.15 – 61.70 °C14) it was easy to

remove it by evaporation14. Since it is commonly known fact that books are more reliable

than websites, the books which were used for investigation were probably more trustworthy.

Usually I tried to find two or more websites with the same information, so it would be more

reliable. However, I did not find at least two pages for every fact, so some claims may be

doubtful.

One more limitation of this experiment is that I did not actually get to know, what is the

amount of caffeine in regular tea cup (hardly someone puts 5 teabags in their cup) – but since

I did not phrase my research question like that (how much caffeine is in REGULAR tea cup),

it is just a minus for me, and actually not for this experiment. There are many improvements

for this experiment – to get more broad-based results more tea sorts should be taken (white

tea, chamomile tea and/or peppermint tea etc.) and only tea bags or smashed tea leaves should

have been used.

17

Bibliography

Websites

1) http://coffeaconsulting.com/assets/images/Caffeine%20molecule.png (collected

16/08/12)

2) http://www.general-anaesthesia.com/people/chloroform.htm (collected 16/08/12)

3) http://tophqbooks.com/books/176032 (collected 16/08/12)

4) http://www.upb.pitt.edu/interior3Default.aspx?menu_id=42&id=7501 CHEM-023

Extraction of Caffeine in Tea (collected 14/05/12)

5) http://www.caffeineguru.com/all-about-caffeine/ (collected 16/08/12)

6) http://www.camh.ca/en/hospital/health_information/a_z_mental_health_and_addiction

_information/caffeine/Pages/caffeine_dyk.aspx (collected 20/09/12)

7) http://www.xula.edu/chemistry/documents/orgleclab/14Caff.pdf (collected 20/09/12)

8) http://www.oxford.net/~mavarod/portal/school/caffeine (collected 20/09/12)

9) http://ic.steadyhealth.com/health_benefits_of_rosehip_tea.html (collected 20/09/12)

10) http://www.thefragrantleaf.com/caffeine.html (collected 20/09/12)

11) Article by A.Smith, ’’Effects of caffeine on human behaviour’’;;

http://intraspec.ca/Effects-of-caffeine-on-human-health.pdf , 1243,1244 and 1251 (

collected 14/10/12)

12) http://www.udel.edu/chem/C465/senior/fall00/Caffeine/Physiological.htm,’’Physiolog

ical effects of caffeine’’ (collected 14/10/12)

Books

1) C.Brown and M.Ford; Pearson Baccalaureate, Higher Level Chemistry developed

specifically for the IB Diploma, 2009, p 642-43

2) Medicine Dictionary (finnish – ’’Lääketieteen termit’’), Medicina, 2004

3) Caffeine, edited by Gene A. Spiller, Ph.D, D.Sc., FACN; Health research and Studies

Center and Sphera foundation, Los Altos, California; CRC Press LLC, 1998

18

Appendix 1 Variables

Independent variable Type of tea (black, green or rosehip)

Dependent variable Amount of caffeine (in mg-s) obtained

Controlled variable(s) The amount of reactants used ( in each

repetition ) – measuring correctly and

considering errors every time

The time tea was brewed and cooled down –

physical control , e.g timer was used

For every type of tea at least 3 measures have

to be done – to get more accurate results

19

Appendix 2 Pictures of the experiment

Above you can see a picture of part 1 of the experiment – tea has just been put on a butan gas

burner to boil.

Above you can see part 2 of the experiment – chloroform layer is at the bottom of the

separatory funnel.