Investigation using TLC to separate photosynthetic pigments

Question 1

Briefly outline a way to use TLC to separate photosynthetic pigments

Answer 1

1) Place plant leaves in mortar
2) Cover leaves with propanone and grind
3) Pour green pigment extract into the funnel into a test tube
4) Pencil line on TLC plate
5) Transfer pigment extract to TLC plate
6) Place TLC plate into the chromatography tank in the fume unit
7) Cover tank with black polythene bag
8) Remove TLC plate and mark position of solvent front
9) Mark position of each coloured pigment

Question 2

What is the TLC plate made of?

Answer 2

Silica

Question 3

What is a risk?

Answer 3

Propanone can cause eye damage
Chromatography solvent can cause lung damage, drowsiness, dizziness, harm to aquatic environment

BOTH are highly flammable

Question 4

Why is a small spot of pigment needed on the TLC plate?

Answer 4

So we can obtain an accurate value for distance measured

Don’t want pigments to overlap

Question 5

Why is propanone used as the extraction solvent?

Answer 5

Separates compounds into their relative solubility’s

Dissolves all pigments

Question 6

Why is the chromatogram run in the dark?

Answer 6

Fades in the light

Question 7

How could you find out whether the separated pigment spots you have observed on your chromatogram are single, pure pigments, or a mixture of 2 or more?

Answer 7

Use different solvent