RP7 Chromatography Of Photosynthetic Pigments

Question 1

What is th purpose of chromatography?

Answer 1

To separate different components in a sample.

Question 2

State the factors affecting the rate of migration of different pigments.

Answer 2

• solubility
• mass
• affinity of the paper

Question 3

What is the formula of Rf value?

Answer 3

Distance moved by pigment/ distance moved by solvent

Question 4

What is the purpose of finding the rf value of a pigment?

Answer 4

• experimental Rf value can be compared to a standard value in a database to identify the pigment.
• the standard value should be measured using the same paper and solvent.

Question 5

Outline the procedure of using chromatography to separate photosynthetic pigments.

Answer 5

1. Draw a horizontal pencil line 1cm above the bottom of the filter paper.
2. Add some acetone and use the mortar and pestle to grind up the leaf sample and release the pigments.
3. Use a capillary tube to transfer the pigment onto the pencil line.
4. Suspend the paper in the solvent so that the level of the liquid does not lie above the pencil line and leave the paper until the solvent has run up the paper to near the top.
5. Remove the paper from the solvent and draw a pencil line marking where the solvent moved up to.
6. Calculate the Rf value for each spot.

Question 6

State the hazards and precautions in this practical.

Answer 6

• solvents are irritant and flammable: keep away from naked flames, wear eye protection and avoid contact with skin.
• leaf extract may be a biohazard: wash hands after