Chromatography of leaves

The paper, dipped in the green solution is covered with layers of different pigments

Scientific name: Pigments contained in green leaves are well separated by paper chromatography

YouTube

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Safety

Wear eye protection goggles.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Step-by-step instruction

  1. Cut the leaves into small pieces, put them in a beaker and pour hot water in the beaker for 1-2 minutes.
  2. Pour the water out and soak the leaves in a little amount of isopropyl alcohol until it lightly covers the leaves. So we can obtain concentrated pigments.
  3. Stir the mixture and wait 1 hour. Isopropyl alcohol should become bright green.
  4. Filter the resulting mixture by using paper filter. Leaves should become almost discolored. Transfer a small amount of the solution into a beaker.
  5. Cut a strip of paper and drop it into the beaker with a solution of the pigment.
  6. Remove the strip from the cup when the solvent rises to 1-2 cm from the top edge. We should recieve approximately the chromatogram: 1 - the starting line, 2 - chlorophyll B, 3 - chlorophyll A, 4 - xanthophylls 5 - carotene.

Scientific background

There is a stationary (in this case it's paper) and movable (isopropanol which rises on the paper) phases in any kind of chromatography. The separation of various substances is due to the different affinity for the mobile and stationary phases.During the process of chromatography, equilibrium is established between the free (dissolved in isopropanol) and related with paper molecules, which determines the average speed for each of the substances to be separated.

So, if at any given time 50% of the molecules are associated with the paper and, accordingly, do not move with the flow, the average speed of the substance is equal to half the isopropanol velocity. Chromatography can be conveniently described by a holding factor. This is the ratio of the distance traveled by a substance to the distance traveled by the solvent.

The leaves contain a variety of pigments that can be separated by this method. Therefore, the leaves turn yellow in fall.

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Published on 13 June 2015

  • Fire
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