F324 Unit 4: Chromatography

  • Created by: Saoirse
  • Created on: 08-06-14 13:25


  • Chromatography is an analytical technique that separates components in a mixture
  • During chromatography a mobile phase sweeps a mixture over a stationary phase
    • Stationary phase is fixed in place and does not move
    • Mobile phase moves in a definite direction
  • Different components have different affinities for a stationary and mobile phase
    • S.P. interacts with components in the mixture and slows them down.
      • Greater the interaction, the more components are slowed down - so components move over at different speeds + are separated

In Thin Layer Chromatography (TLC): S.P is a solid, M.P is a liquid

In Gas Chromatography (GC): S.P is liquid or solid on solid support, M.P is a gas.

Efficient separaration depends on 2 main factors:

  • Adsorption for a solid S.P
    • This is the process by which a solid holds the molecules of a gas solute as a thin film of the surface of a solid.
  • Solubility for a liquis S.P

Thin Layer Chromatography:

  • S.P is a solid: thin layer of an adsorbent e.g silica gel or alumina
  • M.P is a liquid solvent

Producing chromatogram:

  • As the solvent rises it meets the spot of sample and the components in mix are swept along with the solvent.
  • Separation is acheived by adsorption - some components bind strongly, some weakly and the result is different components are separated and travel different distances up plate.
  • Each separated component is seen as a spot on the TLC plate. Use colours or UV radiation to show up by fluorescence.



No comments have yet been made