Chromatography of photosynthetic pigments
Technical & Teaching Notes
Introduction and context
In this practical, students use Thin Layer Chromatography (TLC) to separate photosynthetic pigments from grass.
They take measurements from and observations of the chromatogram to suggest the possible identity of each pigment
separated.
It is interesting for students to see the range of pigments that can be separated from our ubiquitous “green grass”,
highlighting the importance of separating molecules to see what is present. In this method an organic solvent is used
for extraction and for running the chromatogram, so pigments that run successfully are the non-polar, membranebound, photosynthetic pigments not the polar, vacuolar, anthocyanin colouration pigments.
As well as comparing the photosynthetic pigments present in different plant species or varieties, extension activities
could include comparing photosynthetic pigment extraction with anthocyanin extraction and the possibility of
identifying photosynthetic pigments from other non-plant sources.
Safety Notes
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The solvents used to extract the pigments from the leaves and run the chromatogram are highly flammable.
Ensure that there are no naked flames or other sources of ignition in the laboratory.
Wear eye protection when using the solvent.
Avoid inhaling vapour as much as possible by minimising the quantity of solvent used and minimising the
escape of the vapour.
Ensure laboratory is well-ventilated.
The vapours may cause drowsiness or dizziness.
Check CLEAPSS guidelines (Hazcards 45A and 85) for further guidance on the use, preparation, and disposal of the
extraction and running solvents.
Apparatus – per chromatogram
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1 x Thin Layer Chromatography strip ~ 13mm x 67mm*
Glass specimen vial (~2cm x 7.5cm) / universal vial
Cork / bung for glass vial, cut in half lengthways
Pestle and Mortar
0.5g fresh grass leaves (from a succulent grass lawn ~5 pinches, or other green plant material)
Dissecting scissors
Silver sand – a pinch
Propanone – approximately 2cm 3
2x Plastic pipettes (3cm3) one for propanone and one for the running solvent
1cm3 (approx.) running solvent (5 cyclohexane: 3 propanone: 2 petroleum spirit 80-100°C by volume) – per
chromatogram depending on glassware used
Plastic micro-pipette tip/ fine glass pipette
White tile
Pencil & ruler
*TLC plates are commonly available as 40mm x 80mm plates (50 per box), each plate can be economically cut into 3
strips lengthways to provide a plate for each student - adjust in length to fit your vials (see supplier details below).
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 1
Other apparatus for extension activities
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It may be possible to extract carotenoids from other plant material using this method (e.g. carrots, maize,
dandelions, buttercups, bananas, sweet potatoes, cantaloupe melons, tomatoes)
It may be possible to extract anthocyanins from red or blue fruits, flowers and leaves but a different extraction
and running solvent would be required as these anthocyanins are much more polar molecules (CLEAPSS has
suggestions for anthocyanin extraction solvents). Strawberries or the leaves of Coleus sp. could be used.
It may be possible to extract carotenoids from egg yolks or butter using this method and a comparison of the
types of carotenoids found in eggs from hens reared in different conditions (e.g. barn, free range, corn fed)
may be an interesting investigation.
Suppliers
TLC plates
Thin layer Chromatograph plates are available from standard school science suppliers; we recommend the Macherey
Nagel POLYGRAM brand, product code 805021. Costs for these vary between suppliers, but average around £40 for
a pack of 50 plates (cutting the plates into 3 gives an end cost of around 25p per run). See for example Timstar
http://www.timstar.co.uk/ch44017-chromatography-tlc-plates-polygram-pre-coated.html .
Chromatography vessels:
Glass specimen vials or wide necked McCartney vials are ideal, but any glass vessel or approx. 2x7.5cm will suffice.
Drosophila culture vials are also ideal for this purpose. Cork stoppers/bungs (if available) are easiest to split in half
lengthways to hold the TLC plate.
Teaching Notes
General practical tips
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Selecting the plant material – grass is suggested, partly as this is ubiquitous so students will see it regularly
and may relate this back to their chromatogram. Also because it produces a good range of different pigments
when developing the method. Any plant material can be tried and it may be useful to trial different species to
see what works well at the time you are carrying out the practical. Spinach can work well, we suggest using
bagged ‘organic’ spinach (‘organic’ leaves tend to be freshest, and not pre-treated with bleaches).
Time frame to collect data – The extraction of the photosynthetic pigments should only take 2-3minutes, the
spotting on the TLC plate will take a further 3 minutes or so depending on the rigour of drying between each
spot and the number of spots re-applied. The chromatogram will take a couple of minutes to set up and then
about 8 minutes to run. Removal of the chromatography plate, marking the location of the solvent front and
each pigment spot should be done quickly ideally within a minute.
Drying and concentrating spots – the results are clearer if the spot is small and concentrated. The
chromatogram will still show the spread of pigments if there is a bit of spreading but students should try their
best to make the spot as small and as concentrated as possible (~3 mm dia. max).
Solvents can be dispensed using plastic pipettes, students should be encouraged to use the minimum
volumes required – just enough to produce a liquid in the bottom of the mortar and just enough running
solvent to so it will touch the chromatography plate in the glass vial.
Measuring the solvent front – the front starts evaporating immediately on removal of the plate from the glass
vial. Within a couple of seconds the solvent front shrinks lower and will disappears within a few more seconds.
Students need to be made aware that recording the location of the solvent front is a critical point in the
practical.
When to stop the chromatogram – running the chromatogram for longer gives better separation of the
pigments but it is critical to stop the chromatogram before solvent front reaches the cork/bung – further than
this will prevent measurement of the solvent front, so Rf values cannot be calculated. Time spent running the
chromatogram is not critical as the calculation of Rf values standardises this, however students should keep
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 2
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an eye on their chromatogram and remove it when the location of the solvent front is approaching the cork
bung.
Measuring distances – measuring the distance each pigment spot and the solvent front has travelled to the
nearest mm is an appropriate level of accuracy. If spread widely the centre of each pigment spot should be
used to determine the distance each pigment has travelled. As some pigments fade each pigment band
should be recorded lightly by pencil on one side of the plate.
Rf Values – The Rf values obtained by students may be dependent upon the specific TLC plates used, the
temperature of the laboratory and the age of the running solvent. Accompanying Student Notes give a
suggested range of Rf values for each photosynthetic pigment using this method, these ranges may vary
under different conditions.
Students may need to be taught or reminded about:
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Calculating Rf values
Polar and non-polar molecules
Calculating percentage error
Notes on student tasks
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As a minimum students should extract the photosynthetic pigments from grass, measure the distances the
pigment spots and the solvent front have travelled, calculate Rf values and use these values, as well as colour
observations, to make suggestions for the identity of each pigment spot.
This activity should take about 20mins in total.
Extension activities:
o Students could run several chromatograms simultaneously with minimal increase in the total practical
time - different students could carry out extraction of different plant materials with all extracts then
available to all students.
o Students could consider the relationship between Rf value and molecular structure for each of the
photosynthetic pigments. This protocol uses a non-polar extraction and running solvent. The solvent
extracts relatively non-polar molecules such as the photosynthetic pigments embedded within the
thylakoid membrane of chloroplasts. It is straightforward to explain the relative Rf values of the
different carotenoids based on their molecular structure as well as the relative Rf values of the
chlorophylls and pheophytins based on their molecular structure. It is more difficult to develop
suggestions to explain the relative Rf values of the different carotenoids in comparison to the different
pheophytins and chlorophylls. (see the “Background information” section for further discussion of the
categories of photosynthetic pigments and their molecular nature)
o One potential extension is to compare extraction of both the relatively non-polar photosynthetic
pigments and the polar anthocyanins (used by plants for colouration). A different extraction and
running solvent would be needed to extract anthocyanins. Extending the practical in this way would
help encourage students to think carefully about the nature of chromatography, how it separates
molecules. It also helps students to make the link between the chemical nature of the pigments and
how this determines how they can be extracted (and their Rf value with a particular solvent).
Additionally links can also be made between the function and location of the pigments in plant –
photosynthetic pigments being non-polar due to the functional requirement that they are membranebound, with anthocyanins being polar as they are accumulated in the watery contents of the vacuole.
o Further potential investigations could be to study the carotenoids found in egg yolks. Using grass as a
standard it could be possible to make suggestions regarding which carotenoids may be present or
absent in egg yolks. It may also be possible to compare barn reared, free range and corn fed hens
eggs to see if there are differences in carotenoids present. Maize may be used as a comparison. It
may also be possible to incorporate work with a colorimeter to investigate quantities of pigments
present.
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 3
Possible questions for students
1. Follow the protocol and answer the following questions
Name the method of chemical separation you have used.
What species did you investigate?
Why is it important to use an organic (non-polar) solvent and not a polar one like water?
What is the sand for? How could you prove that the pigments came from the plant material and not the sand?
Why is it important to mark positions in pencil rather than pen (particularly that starting position of the concentrated
extract)?
Why is repeated application of the plant extract onto the same spot required?
Why is it important to let the spot dry in between each repeated application of the plant extract?
Why is it important that the spot of plant extract is above the surface of the solvent when the chromatography plate is
placed in the vial?
Why is it important that the chromatogram is stopped before the solvent front reaches the top? What would happen to
the pigment spots if the chromatogram was left running for a long time?
Why is it important to mark the solvent front quickly?
Why is it useful to mark the positions of the pigment spots or take a photograph of the chromatogram soon after it has
been run?
How accurate is your measurement of the distance the solvent front has travelled and how far each pigment spot has
travelled (to the nearest 1cm, 0.1cm, 0.01cm or something different)? (Consider the limitations of the ruler you’re
using and the difficulty in locating the exact position of the solvent front or centre of the pigment spot).
How do you calculate an Rf value?
How could you modify the equipment/experiment, only very slightly in order to get more accurate measurements of the
Rf values for each pigment?
What is the percentage error in the Rf values you get for each pigment spot?
What safety precautions did you, and the class as a whole take when using the solvent? Include ways in which you
reduced the amount of solvent that evaporated into the air.
2. The findings from your investigation
How many different pigment spots did you obtain?
Have you managed to identify any pigments? If so which ones and how confident are you about their identity? What
factors affect your confidence (both positively and negatively)?
Is it possible to have an Rf value greater than 1? Explain.
Does it matter if different chromatograms are run for different lengths of time? Explain.
What could be done to confirm the identity of each pigment if the results were unclear or if two molecules were a
similar colour and/or their Rf values were very similar?
If you were interested in the concentration of each pigment in the plant material what practical technique could you
use?
3. The Biology of photosynthetic pigments and exploring the photosynthetic molecules
Where, exactly have you extracted the photosynthetic pigments from?
How does the fact that these pigments dissolve in an organic (relatively non-polar solvent) help explain the precise
location of these pigments in plant cells?
Assuming that the distance the pigment travelled is based on the solubility of the molecule in the organic solvent
suggest what might be concluded about the differences in structure between different pigments.
What is the role of these photosynthetic pigments in photosynthesis?
Why is it useful for a plant to have several different photosynthetic pigments?
How do the molecular structures of chlorophyll a and b differ? Explain why chlorophyll a has a larger Rf value than
chlorophyll b? (show molecular structures) (clue: relatively non-polar solvent = mobile phase and a relatively polar
stationary phase = the TLC plate).
How do the molecular structures of the chlorophylls vary in comparison to the pheophytins explain why the
pheophytins have a larger Rf value than the chlorophylls? (show molecular structures) (clue: relatively non-polar
solvent = mobile phase and a relatively polar stationary phase = the TLC plate).
How does the molecular structure of beta-carotene explain why it has such a large Rf value? (show structure) (clue:
relatively non-polar solvent = mobile phase and a relatively polar stationary phase = the TLC plate).
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 4
How do the molecular structures of the 3 different xanthophylls explain why they all have relatively small Rf values and
how do the 3 different structures explain the order in which these pigments appear in the chromatogram? (show
structures and give clue as above. Also extra information is likely to be required: Hydroxyl (OH) and epoxy (C-O-C in a
triangle) groups are polar groups and the hydroxyl group is more polar than the epoxy group.
4. Exploring pigments in other biological material
Other plant pigments called anthocyanins are not membrane bound, relatively non-polar molecules, but are pigments
that are polar and dissolved in the watery contents of plant vacuoles. What would you need to do to modify this
experimental method in order to investigate anthocyanins in leaves of flowers?
Design an experiment to determine whether the red of strawberries and the red of tomatoes is the same pigment
molecule.
If you got a pigment spot from one of the strawberry or the tomato but not the other it might be possible that the
pigment from the one without the spot is still the same molecule but is held more tightly within the cells or organelles
and so just didn’t move up the chromatography plate. What other reason could there be for a pigment not moving from
the original location and what could you do to further investigate if this was the case?
Do some research into colour pigments in the natural world. Investigate keywords such as carotenoids, carotenes and
xanthophylls, flavonoids, anthocyanins, and anthoxanthins. Pick 3 interesting facts to share.
Design an experiment to determine whether the yellow of hen egg yolk is the same molecule as any of the yellow
pigments found in grass. Extend the design of this experiment to be able to investigate whether eggs from hens
reared in different conditions (e.g. barn, free-range, corn fed) have different pigments in their yolks. Incorporate into
the design a way to see if the yellow pigment in this corn (sweet corn/maize) is different to any of those found in grass.
You could also research this online.
Would it be possible to use this experiment to see if artificial “yolk-yellowers” are added to the feed of some hens?
Would it also be possible to use this experiment to see if supplements of the natural “yolk-yellowing” pigments are
added to the feed of some hens?
How could quantities of pigments in egg yolk be investigated rather than just presence or absence of a particular
pigment?
Science & Plants for Schools: www.saps.org.uk
Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 5
Getting learning value from the practical
It is important to consider the purpose of practical work in Biology lessons and the following information provides
suggested areas where this practical can be used to help students develop their practical, mathematical and subjectknowledge-based skills and understanding. The latter part of this section shows how this practical (or an extension of
it) can also be used to meet some of the A-level specification requirements for the Use of apparatus and techniques
as well as the Common practical assessment criteria (CPAC).
PRACTICAL SKILL DEVELOPMENT
You should be able to:
 use a pestle and mortar to extract photosynthetic pigments from plant material
 follow instructions carefully to successfully produce a chromatogram of photosynthetic pigments from the plant
extract
 accurately measure the distance between the solvent front and the original concentrated extract spot as well as the
distance between each pigment spot and the original concentrated extract spot
 calculate Rf values for each of the pigment spots
 Compare calculated Rf values with those of known pigments to suggest the identity of each molecule
 record Rf values, observations and suggested identity of pigments in a suitable table
 use information about the nature of each molecule to explain their Rf values relative to other similar molecules
EXTENSION TO PRACTICAL SKILL DEVELOPMENT
You should be able to:
 suggest ways to improve the accuracy of the Rf values calculated
 suggest factors that would need to be controlled, and/or modifications to the method if comparisons of pigments
from different sources were to be made
 describe a suitable control experiment to ensure that the pigment come from the plant extract and not from other
equipment or chemicals used in the process
 design an experiment to investigate the possible presence of both polar and non-polar pigments in different plant
extracts (e.g. comparing tomatoes and strawberries)
 design an experiment to explore the pigments in hen egg yolks and how this may relate to how the hens are reared
and/or what they are fed
 design an extension to the main experiment, or any of the others mentioned above to investigate the concentration
of particular pigments rather than just their presence or absence
MATHS SKILLS DEVELOPMENT
You should be able to:
 calculate Rf values for each of the pigment spots
 calculate the percentage error in the measurements taken
EXTENSION TO MATHS SKILL DEVELOPMENT
You should be able to:
 work out a range for each Rf value that would include the true Rf value for that chromatogram
 calculate the percentage error in the Rf values calculated
ASSOCIATED SUBJECT KNOWLEDGE DEVELOPMENT
You should be able to:
1. State the precise location of the pigments involved in photosynthesis within the leaf
2. Name 5 photosynthetic pigments (or types of pigment) found in leaves
3. Outline the role of the leaf pigments in photosynthesis
4. Explain how the terms “light harvesting systems”, “photosystems” and “reaction centres” are related
5. Explain why many plants have a variety of photosynthetic pigments
6. Describe how to conduct chromatography to separate pigments from a leaf, explain importance of each step
7. List 3 characteristics of the solute (in this case a pigment) that influences how far it travels during
chromatography, and for each describe the effect it has
8. Describe how to calculate the Rf value for a particular substance
9. Explain how a chromatogram can be used to identify an unknown substance
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 6
RECORDING EVIDENCE OF STUDENTS’ WORK
Students can use the worksheet provided to produce evidence of their work in this practical that can contribute to their
practical skills accreditation.
MEETING ASPECTS OF THE USE OF APPARATUS AND TECHNIQUES
The full practical can allow students to meet various components of Appendix 5c of the GCE AS and A level subject
content for biology, chemistry, physics and psychology (DfE, April, 2014) in bold (with clarification where needed):
1. Use appropriate apparatus to record a range of quantitative measurements (to include mass, time,
volume, temperature, length and pH).
2. Use appropriate instrumentation to record quantitative measurements, such as a colorimeter or potometer.
3. Use laboratory glassware apparatus for a variety of experimental techniques to include serial dilutions.
4. Use of light microscope at high power and low power, including use of a graticule.
5. Produce scientific drawing from observation with annotations.
6. Use qualitative reagents to identify biological molecules.
7. Separate biological compounds using thin layer/paper chromatography or electrophoresis.
8. Safely and ethically use organisms to measure:
a. Plant or animal responses
b. Physiological functions
9. Use microbiological aseptic techniques, including the use of agar plates and broth
10. Safely use instruments for dissection of an animal organ, or plant organ.
11. Use sampling techniques in fieldwork.
12. Use ICT such as computer modelling, or data logger to collect data, or use software to process data.
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 7
MEETING ASPECTS OF THE COMMON PRACTICAL ASSESSMENT CRITERIA (CPAC)
Competency
Practical Mastery
Follows
written
procedures
Correctly follows instructions to carry out the
experimental techniques or procedures.
Applies
investigative
approaches
and methods
when using
instruments
and
equipment
Correctly uses appropriate instrumentation,
apparatus and materials (including ICT) to carry
out investigative activities, experimental
techniques and procedures with minimal
assistance or prompting.
Caries out techniques or procedures methodically,
in sequence and in combination, identifying
practical issues and making adjustments when
necessary.
Identifies and controls significant quantitative
variables where applicable, and plans approaches
to take account of variables that cannot readily be
controlled.
Selects appropriate equipment and measurement
strategies in order to ensure suitably accurate
results.
Evidence from this practical / or
opportunity to train students in this
skill using this practical
Observational evidence from the teacher.
Positive outcome for the student’s
chromatogram.
Being able to answer questions about the
procedure.
Use of pestle and mortar, running the
chromatogram and measuring Rf values.
Follow procedure – set up the
chromatography plate in the glassware
appropriately, adjusting during trial if
necessary.
If comparing between plant
species/varieties then running on the
same plate or ensuring the same protocol
is followed. Standardising extraction
method.
Can answer questions about modifications
to increase the accuracy of the Rf value
measurement and to clarify the
identification of the different pigments.
Can answer questions about the risks from
this practical and the safety precautions
taken.
Safely uses a
range of
practical
equipment
and materials
Identifies hazards and assesses risks associated
with these hazards when carrying out
experimental techniques and procedures in the
lab or field.
Uses appropriate safety equipment and
approaches to minimise risks with minimal
prompting.
Identifies safety issues and makes adjustments
when necessary.
Evidence from actions that minimise use
and evaporation of the extraction and
running solvent.
Makes and
records
observations
Makes accurate observations relevant to the
experimental or investigative procedure.
Accurate descriptions of colour and
measurements of distances the solvent
front and the pigments travel.
Measurements and observations from the
chromatogram taken and recorded and
used appropriately to make suggestions
about the identity of the pigments.
Report writing packages (e.g. Word).
Internet search engines.
Researches,
references
and reports
Obtains accurate, precise and sufficient data for
experimental and investigative procedures and
record this methodically using appropriate units
and conventions.
Uses appropriate software and/or tools to process
data, carry out research and report findings.
Sources of information are cited demonstrating
that research has taken place, supporting
planning and conclusions.
Referencing in final report or presentation.
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 8
Background information
The learning outcomes document for this practical summarises the key background information relating to the
chromatography of photosynthetic pigments.
Rf value terminology – The definition of an Rf value, based on how it is calculated, is consistently applied throughout
the literature however what the “R” and the “f” stand for varies from source to source. You may find it referred to as
“relative front”, “rate of flow”, “retention value” or “retardation factor”.
Below is information about the different pigments that may be useful when discussing the reasons behind the relative
distances the different pigments travel in the chromatogram.
The chlorophylls (a and b) and pheophytins (a and b) are very similar molecules (figure 1A-C). They all have a
porphyrin-like ring structure (a complex ring of carbon atoms with 4 Nitrogen atoms near the centre) with a long
hydrophobic hydrocarbon tail. The chlorophylls have a magnesium atom at the centre of the porphyrin-like ring
whereas the pheophytins are missing the magnesium atom and have two hydrogen atoms instead. As well as the
magnesium and nitrogen atoms there are some oxygen atoms around the ring that contribute to the polar nature of
this part of the molecule. The absence of the magnesium atom in the pheophytins makes them less polar than the
chlorophylls and so they have a larger Rf value in the solvent used here. Chlorophyll b and pheophytin b have one
more oxygen atom around the ring than their a equivalents, making them more polar than their a equivalents, so they
have smaller Rf values than their a equivalents.
Pheophytins used to be considered solely as breakdown products of chlorophyll, however, they are now considered to
be early electron acceptors of photosystem II (they may still be breakdown products as well).
Carotenoids are a group of molecules with 40 carbon atoms arranged, mostly, linearly, often terminating at each end
in a 6 carbon ring. The linear component has alternating carbon-carbon single and double bonds. These molecules
act as both antenna pigments and photoprotective agents as well as giving colour to plant structures. The carotenoids
are split into two groups: the carotenes (hydrocarbons) and the xanthophylls (molecules that also contain some
oxygen atoms). The carotene in grass is mostly beta-carotene (figure 1D) and, being a hydrocarbon, is non-polar and
so has a very large Rf value. The xanthophylls most abundant in grass, are lutein, violaxanthin and neoxanthin (figure
1E-G). Being xanthophylls they all contain oxygen atoms, making them polar so they have relatively small Rf values.
The least polar of the 3 common xanthophylls is lutein with one hydroxyl group at each end of the molecule only,
therefore lutein has the largest Rf value of these 3 xanthophylls. As well as the two hydroxyl groups that lutein has,
violaxanthin has two epoxy groups (carbon-oxygen-carbon in a triangle). Neoxanthin has 3 hydroxyl groups and one
epoxy group. Epoxy groups are polar, but not as polar as hydroxyl groups so neoxanthin is the most polar of the 3
xanthophylls and therefore has the smallest Rf value of these 3 molecules.
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 9
A
B
C
D
E
F
G
Figure 1: A: chlorophyll a; B: Chlorophyll b; C: pheophytin a; D: Beta carotene; E: Lutein; F: Violaxanthin; G:
Neoxanthin.
(Images A-E and G: Wikimedia Commons / Public Domain, Image F: author – Yikrazuul
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Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 10
)
Sample data
Figure 2: A chromatogram from grass
The Chromatogram to the left (figure 2) and the table below shows data collected from grass picked
from an amenity lawn outside the laboratory in July, using propanone as the extraction solvent, no
sand, and the suggested running solvent (5 cyclohexane: 3 propanone: 2 petroleum ether 80100°C). It was run for about 8mins and photographed very soon after removal from the running
solvent. The solvent front travelled 44mm.
Pigment colour
Bright yellow
Grey
Pale Brown
Blue green
Yellow
Green
Pale yellow
Pale yellow
Distance
pigment has
travelled / mm
41
20
16
12
11
10
7
3
Rf value
0.93
0.45
0.36
0.27
0.25
0.23
0.16
0.07
Suggested identity of the pigment
Carotene
Pheophytin a
Pheophytin b
Chlorophyll a
Xanthophyll – Lutein
Chlorophyll b
Xanthophyll – Violaxanthin
Xanthophyll – Neoxanthin
Further Investigations
As mentioned within this document there is scope to develop this practical in a range of directions including:
 Investigating the presence of carotenoids in other plant material (e.g. carrots, maize, dandelions, buttercups,
bananas, sweet potatoes, cantaloupe melons, tomatoes).
 Investigating the presence of carotenoids in animal products (e.g. egg yolk and butter) and possibly
comparing eggs produced by hen reared in different conditions (e.g. barn, free range, corn fed).
 Comparing the pigments extracted using polar and non-polar solvents to investigate and compare
anthocyanins and the photosynthetic pigments (e.g. comparing the red of tomatoes (lycopene, a non-polar
carotenoid) and the red for strawberries (an anthocyanin), or investigating both photosynthetic pigments and
anthocyanins in Cloeus spp.)
References
Davies, K. (ed) (2004) Plant pigments and their manipulation. Annual Plant Review, Vol. 14.
Tomkins, S. P. and Miller, M. B. (1994), A rapid extraction and fast separation of leaf pigments using thin layer
chromatography. School Science Review 75 (273), 69 - 72. (Available from the SAPS website)
Acknowledgements
Protocol and support materials re-developed by Dr Chris Graham, Long Road Sixth Form College, Cambridge and
Gail Webdell, Faculty of Education, University of Cambridge. Based on an original protocol developed by Stephen
Tomkins, Homerton College, Cambridge, and Barry Miller, Douglas Ewart High School, Newton Stewart.
Science & Plants for Schools: www.saps.org.uk
Chromatography of photosynthetic pigments – Teaching and Technical notes: p. 11