Paper chromatography

• Chromatography used 2 phases and separates the substances in a mixture to identify the substances
• Two phases

  • mobile phase- where the molecules can move. this is always a liquid or a gas
  • a stationary phase- where the molecules can’t move. solid or thick liquid
• During chromatography the substances in the sample constantly move between the 2 phases- an equilibrium is formed between 2 phases
• The mobile phase moves through the stationary phase and anything dissolved in the mobile phase moves with it. how quickly a chemical moves depends on how it’s distributed between the two phases- whether it spends more time in the mobile or stationary phase
• The chemicals that spend more time in the mobile phase will move further
• The components in a mixture will normally separate through the stationary phase so long as all the components spend different amounts of time in the MobiE phase
• A pure substance will only ever form one spot
• During paper chromatography the stationary phase is the chromatography paper and mobile phase is the solvent
• The amount of time the molecules spend in each phase depends on two things:

  • how soluble they are in the solvent
  • how attracted they are to the paper