Required Practical 7 - Use of chromatography to investigate the pigments isolated from leave of different plants.

Question 1

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

Answer 1

• Solubility
• Mass
• Affinity to paper.

Question 2

What is the purpose of finding the RF value of a pigment.

Answer 2

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 3

Outline the procedure of using chromatography to separate photosynthetic pigments.

Answer 3

• Draw a horizontal pencil line 1cm above the bottom of the filter paper.
• Add acetone and use the pestle and mortar to grind the leaf sample and release the pigments.
• Use a capillary tube to transfer the pigment onto the pencil line.
• Suspend the paper in the solvent so the solvent doesn’t lie above the pencil line.
• Remove the paper from the solvent when it has run up the paper to a pencil line 1cm from the top.
• Calculate the RF value for each spot.

Question 4

State the hazards and precautions in this practical.

Answer 4

• Solvents and 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 use.