18/03/2026
Question 2: Experiment to Show Green Leaves Contain Three Pigments
Procedure:
1. Obtain a fresh green leaf (e.g., spinach) and cut it into small pieces.
2. Place the leaf pieces in a mortar, add a small amount of sand and 10 ml of acetone (or ethanol) as a solvent, and grind thoroughly to extract the pigments.
3. Using a capillary tube, apply a concentrated drop of the extract on a chromatography paper strip about 2 cm from one end. Allow it to dry and repeat spotting several times to get a concentrated spot.
4. Suspend the paper strip in a chromatography jar containing a small amount of solvent (e.g., petroleum ether and acetone mixture) such that the spot is above the solvent level. Cover the jar.
5. Allow the solvent to rise up the paper until it nears the top. Remove the paper and mark the solvent front.
6. Observe the separated pigments under visible light and also under ultraviolet light (if available) to see fluorescent bands.
Expected Results:
· Several distinct bands of different colours appear on the chromatogram. Typically, four pigments are visible: carotene (orange-yellow), xanthophyll (yellow), chlorophyll a (blue-green), and chlorophyll b (yellow-green). However, the question specifies "three pigments," so you may focus on the three most prominent ones (often carotene, xanthophyll, and chlorophylls) or note that sometimes the chlorophylls separate into two. Under normal conditions, at least three bands are clearly seen.
· The pigments separate based on their solubility and affinity to the paper.
Conclusion:
The green leaf contains multiple pigments, including chlorophylls and carotenoids, which can be separated by chromatography. This demonstrates that leaves have more than one pigment, contributing to photosynthesis and light absorption.
