Description: The purpose of this experiment is to determine the types of pigments found in various vegetation. The students will gather plants, soak them in acetone and use coffee filter strips to separate the pigments. Then the students will determine the pigments found in each type of leaf. The pigments found in spinach leaves, lettuce leaves and marigold leaves are all different. Paper Chromatography is a technique that enables us to separate plant pigments. The pigments found in plants vary and the process of chromatography is important in the detection of the types of pigments found in each.
Needed Materials: Acetone fingernail polish remover, test tubes or other empty containers (enough for 5 containers per group), felt tip markers, coffee filters, pigment guide, masking tape, scissors, spinach leaves, mum leaves, iceberg lettuce and leaves of various plants found in your schoolyard.
Safety Rule: Avoid inhaling the vapors from the acetone and spilling it on your clothing.
Procedure:
Student Information: The following information will provide you with the steps for conducting your plant chromatography experiment. It is important to hold all of the variables constant except for those that are being manipulated. Constant (or controlled variables) would be such things as: the length of the filter paper strip, the amount of time the paper is left in the solution, the amount of acetone in the container, the size of the container being used, etc. Manipulated (or independent) variables would be those things that we change to see if the response will be different, such as: type of plant being studied. The responding (or dependent) variable for this experiment will be the different pigments found in each of the different types of vegetation.
The reporting form for this experiment is set up so that you can determine how many different kinds of vegetation you would like to use, the kind of container you would like to use and how long your strips of filter paper will be. Also remember that a good scientific experiment is repeated a minimum of three times. Therefore, your data will be more accurate if you conduct several experiments that are exactly the same and then compile an average of your data before submitting it.
Procedural Steps for Conducting the Investigation
- 1. Collect two different plants from your schoolyard. You are going to test these two plants along with the spinage, mum leaves, and iceburg lettuce.
- 2. Label each container with the kind of plant you are testing.
- 3. Place a different leaf in the bottom of each test tube and crush it.
- 4. Pour about 2 cm. of acetone (fingernail polish remover) into each of your test tubes.
- 5. Let this sit twenty-four hours.
- 6. Cut five strips out of the middle of a coffee filter.
- 7. Place the end of one coffee filter strip in each of the test tubes. The solvent will travel up the paper, and as it does, it will dissolve and deposit the separate pigments.
- 8. After twenty-four hours, check your results.
- 9. Remove the strips of paper from the test tubes and lay them on dry paper towels that are labeled with the type of plant extract found on that strip.
- 10. Use a magnifying glass and a pigmentation guide to determine the types of pigments in each extract.
Discussion Questions
- What were your conclusions for this experiment?
- What could you infer based on your conclusions?
- How would you design this experiment differently the next time?
- What types of pigments were found in each type of plant?
- Did the color of the leaf affect the pigments found it them?
- If the answer to the above question is “yes”, which leaves had the most variation in the kinds of pigments found in them?
- Did certain leaves have the exact same pigments?
- If the answer to the above question was “yes”, were the leaves similar in other ways?
- Do you think the amount of sunlight a plant receives affects the pigments found in the plants? How could you test your predictions experimentally?
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- Would you expect to find the same results year round? How could you test your predictions experimentally?
