Chromatography relies on two different ‘phases’:
The different dissolved substances in a mixture are attracted to the two phases in different proportions. This causes them to move at different rates through the paper.
Separation by chromatography produces a chromatogram. A paper chromatogram can be used to distinguish between pure and impure substances:
A paper chromatogram can also be used to identify substances by comparing them with known substances. Two substances are likely to be the same if: