Name ______Lab
CHROMATOGRAPHY OF PLANT PIGMENTS
background information:
Looking at chloroplasts under a microscope or examining a plant leaf, the only color which appears to be present is chlorophyll, a green pigment. However, there are other pigments in a leaf. Yellow and orange pigments, not normally seen are usually present within the chloroplasts. Separating and identifying these substances is a way of analyzing the process of photosynthesis. The pigments which are the most soluble in the solvent will travel the fastest. Chromatography is a method of separating substances from each other.
PROBLEM:
What plant pigments ex: chlorophyll a (blue-green), chlorophyll b (yellow-green), carotene (orange-yellow), and xanthophylls( yellow), will separate on the chromatogram?
HYPOTHESIS: ______
______
Write down your hypothesis as to what plant pigments are present in spinach and which pigment is the most prevalent).
MATERIALS:
Isopropyl alcohol (solvent) Spinach leaf extract Filter paper Test tube Stopper Beaker Scissors Toothpick
Metric ruler Graduated cylinder
PROCEDURE:
1. Cut a strip of filter paper narrow enough to fit inside the t.t. without
touching the sides; 2 cm. shorter than the test tube.
2. Cut an arrow shape at one end and cut two small notches about 2cm
from the bottom. Mark a pencil point in the middle of notches. Write
the groups names at the top of the strip in pencil.
3. Using a toothpick add the chlorophyll extract on the mark. Keep the spot the size of a pencil eraser end.
4. Let spot dry 30 seconds and repeat 10 more times, until dark green.
5. Put 2 ml. of the solvent (alcohol) into the test tube. Place filter paper
strip into the test tube, Make sure the chlorophyll spot is NOT
submerged in the solvent Place stopper on top. Place in t.t. rack.
6. Leave the chromatogram set-up for at least 15 minutes.
7. Remove the strip. Observe the spots of color. Draw a circle around
each spot and label its color
ANALYSIS AND CONCLUSION QUESTIONS:
1. Draw a picture of your chromatogram and label the pigments.
2. Is chlorophyll composed of one or several pigments?
3. What proof do you have? ______
4. Why do you think pencil, but not ink, was used to make marks on the
chromatogram? ______
5. Which pigment in YOUR experiment was the most soluble? ______
6. Which pigment in YOUR experiment was present in the greatest amount.
7. What is the role of Chlorophyll A?
______
8. Many leaves change color in the autumn. How is it possible for this color change to happen? Base your answer on your knowledge of pigments present in the chloroplasts. (HINT: chlorophyll a and chlorophyll b are easily broken down by the cooler autumn temperatures). ______
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