Chromatography

Describe the method for chromatography - 6 marks

1. Draw a pencil line near the bottom of the chromatography paper.

2. Place a small spot of the dye/ink mixture on the pencil line.

3. Put a small amount (about 20cm³) of solvent (usually water) in a beaker.

4. Place the paper in the solvent, making sure the spot is above the solvent level and that the bottom of the chromatography paper is only just touchign the surface of the paper

5. Put a lid on the beaker to reduce evaporation.

6. Leave the solvent to travel up the paper for about half an hour.

7. Remove the paper before the solvent reaches the top.

8. Mark the solvent front with pencil.

9. Allow the paper to dry.

10. Compare the separated spots or calculate Rf​ values.

Key safety/accuracy points:

• Use pencil, because ink would dissolve.

• The spot must be above the solvent, so it does not wash into the solvent.

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