Paper Chromatography

Chromatography is a technique to separate molecules based on their size and solubility as they are transported by a flow of solvent. In paper chromatograph the solvent wicks into a piece of paper by capillary action. A mixed sample of chemicals such as a plant extract is placed as at dot at the bottom of the paper. Smaller molecules which are more soluble move with the solvent front up the piece of filter paper. Large molecules get left behind. Eventually the compounds separate into distinct spots.

Paper chromatography procedure
  • Grind up a whole plant leaf or flower in a clear solvent so that chemicals will be dissolved in the solvent.
  • Make a spot of the mixture on a piece of filter paper.
  • Dip the end of the filter paper in the solvent.
  • The solvent will wick up the paper by capillary action and carry the plant chemicals with it.
  • Each chemical will travel at different rate and so the chemicals will separated as they move up the sheet.

Column Chromatography

In column chromatography a large volume of solvent is passed down a tube containing some gel. The sample is placed at the the top of the column. After a certain amount of time the chemicals separate and a portion of solvent that comes out contains a high proportion of the desired chemical. Column chromatography is used to purify larger samples sometimes for manufacturing.