Class XI Practical: Physiology - Chromatography to Separate Plant Pigments

Objective

To separate different photosynthetic pigments (e.g., chlorophyll a, chlorophyll b, carotenoids, xanthophylls) from a plant extract using paper chromatography.

Guidelines

1. Pigment Extraction: Grind fresh leaves (e.g., spinach) with a suitable solvent (e.g., acetone or ethanol) and a small amount of sand to obtain a crude pigment extract.
2. Chromatography Setup:
   • Draw a pencil line near one end of a chromatography paper strip.
   • Apply a concentrated spot of the pigment extract onto the pencil line.
   • Place the paper strip in a chromatography jar containing a suitable solvent mixture (e.g., petroleum ether and acetone) ensuring the solvent level is below the pigment spot.
3. Separation: Allow the solvent to ascend the paper, separating the pigments based on their differential solubility and adsorption to the paper.
4. Observation: Once the solvent front reaches near the top, remove the paper and mark the solvent front. Observe and identify the separated pigment bands by their characteristic colors.
5. Calculation (Optional): Calculate Rf values for each pigment.

Expected Outcome

Successful separation of plant pigments into distinct bands on the chromatography paper, demonstrating the principle of chromatography.