Illustrated Glossary of Organic Chemistry

Chromatography: A method for separation of components in a mixture, based on differences in attraction (retention) of these components for a mobile phase (a phase that flows) and stationary phase (a phase that is immobile). In gas chromatography, the mobile phase is a gas (called the carrier gas; often helium) and the stationary phase is a solid or high boiling point liquid. In HPLC, the mobile phase is a liquid and the stationary phase is a solid.  When the stationary phase is held in a tube of some sort (as in gas chromatography and HPLC) the method is called column chromatography. Other stationary phases can be used, such as paper (in which case the technique is called paper chromatography).

Schematic representation of a gas chromatograph.
The column is shown in red.
A modern gas chromatograph.

Schematic representation of an HPLC instrument.
The column is shown in red.
A modern HPLC instrument.

  Click on the image to view a YouTube video demonstrating column chromatography being used to separate colored compounds. Note the different colored bands, caused by different compounds in the mixtures.