TLC of photosynthetic pigments

Question 1

What is thin layer chromatography (TLC) used for in photosynthesis? (1)

Answer 1

Used to separate photosynthetic pigments

Question 2

What are the mobile phase and stationary phase in TLC? (2)

Answer 2

1. Mobile phase = A liquid solvent that moves,
2. Stationary phase = A solid plate with a thin layer of gel (the chromatography plate) where the pigments cannot move

Question 3

How are photosynthetic pigments separated using TLC? (2)

Answer 3

1. The solvent moves up the TLC plate, carrying the dissolved pigments,
2. Different pigments travel different distances, separating them on the plate

Question 4

How is the Rf value calculated in TLC? (1)

Answer 4

Rf value = Distance travelled by the pigment spot ÷ Distance travelled by the solvent

Question 5

What is the first step in the TLC experiment for separating photosynthetic pigments? (2)

Answer 5

1. Crush the leaf (e.g., spinach) with anhydrous sodium sulphate and propanone,
2. To extract the pigments

Question 6

How do you prepare the chromatography plate with the pigment? (3)

Answer 6

1. Draw a horizontal pencil line near the bottom of the plate,
2. Build up a single concentrated spot of liquid pigment from the plant extract,
3. Letting each layer dry between applications

Question 7

What happens after the pigment is applied to the plate? (2)

Answer 7

1. Stand the plate in a beaker of solvent, making sure the point of origin is just above the solvent level,
2. Cover the beaker to prevent evaporation and allow the solvent to develop

Question 8

How do you finish the TLC experiment? (2)

Answer 8

1. Mark the solvent front with a pencil when the solvent reaches near the top,
2. Then calculate the Rf values to identify the pigments by comparing them to a database