RP 7

• What is the purpose of chromatography?

  To separate different components in a sample.
• What are the factors affecting the rate of migration of different pigments in chromatography?

  • Solubility
  • Mass
  • Affinity to the paper
• What is the formula for calculating the RF value?

  RF value = Distance moved by pigment / Distance moved by solvent
• Why is it important to find the RF value of a pigment?

  It allows the experimental RF value to be compared to a standard value in a database to identify the pigment.
• What should be considered when measuring the standard RF value?

  The standard value should be measured using the same paper and solvent.
• What is the procedure for using chromatography to separate photosynthetic pigments?

  1. Draw a horizontal pencil line 1cm above the bottom of the filter paper.
  2. Grind up the leaf sample with acetone using a mortar and pestle.
  3. Transfer the pigment onto the pencil line using a capillary tube.
  4. Suspend the paper in the solvent without letting the liquid cover the pencil line.
  5. Remove the paper and mark the solvent front with a pencil line.
  6. Calculate the RF value for each spot.
• What are the hazards and precautions when performing chromatography?

  • Solvents are irritant and flammable.
  • Keep away from naked flames.
  • Wear eye protection and avoid skin contact.
  • Leaf extract may be a biohazard; wash hands after use.