Chromatography

• Chromatography is used to separate and identify 2 substances in a mixture.

  • Mobile phase = The moving molecules. Always a liquid or gas
  • Stationary phase = The still molecules. Always a solid or thick liquid
• TLC = Thin Layer Chromatography

  Stationary phase = thin layer of solid

  Mobile phase = Solvent

  1. Draw a line near the bottom of the plate
  2. Put some of the solvent in a beaker and dip the bottom of the plate into the solvent
  3. The solvent will start to move up the plate with some chemicals from the mixture
  4. Eventually, you will see the different chemicals separate out, forming spots at different places on the plate
  5. Remove the plate from the mixture before the solvent reaches the top, and mark the distance that the solvent has moved

  
• Paper chromatography

  Stationary phase = a sheet of chromatography paper

  Mobile phase = solvent
• Rf = distance travelled by solute / distance travelled by solvent
• Gas chromatography

  Mobile phase = unreactive gas

  Stationary phase = viscous (thick) liquid

  1. Unknown mixture injected into a long tube covered with the stationary phase
  2. The mixture moves along the tube with the mobile phase until it comes out the other end, in intervals
  3. The time is takes to travel through is called the retention time
  4. The retention time for each chemical is different, and thats how they are identified