Seperating molecules

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13 Terms

1
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What can chromatography be used for?

To separate out and identify biological molecules

2
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What is the mobile phase in chromatography?

Where the molecules can move

3
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What is the mobile phase in paper/thin layer chromatography? Give 2 examples

A liquid solvent e.g ethanol/water

4
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What is the stationary phase in chromatography?

Where the molecules cannot move

5
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What is the stationary phase in paper chromatography?

Chromatography paper

6
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What is the stationary phase in thin layer chromatography?

Thin layer of solid e.g glass

7
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Explain the first step of paper chromatography to separate amino acids

  • Draw a pencil line near the bottom of the chromatography paper

    • Put a drop of the concentrated amino acid mixture onto the pencil line

8
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Explain the second step of paper chromatography to separate amino acids

  • Add a small amount of the solvent to a beaker and place the chromatography paper in it

  • Cover with a lid to stop the solvent from evaporating

9
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Explain the third step of paper chromatography to separate amino acids

  • As the solvent spreads up the paper, the different amino acids move with it but at different rates so they will spread out

10
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Explain the fourth step of paper chromatography to separate amino acids

  • When the solvent has almost reached the top take the chromatography paper out

  • Mark the solvent front with pencil

  • Leave the paper to dry

11
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Explain the fifth step of paper chromatography to separate amino acids

  • Spray the paper with ninhydrin solution to turn the amino acids purple as they’re originally colourless so hard to analyse

  • Do this in a fume cupboard

12
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What do you use to identify the seperated molecules?

Rf values

13
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Rf value calculation?

distance moved by the solute/distance moved by the solvent