Chromatography is a method used for separating ( and identifying) components of a mixture based on how they interact with two phases :
Paper Chromatography
Paper chromatography is a relatively simple and economic separation technique used to separate and identify mixtures of soluble substances, such as inks, dyes, amino acids, or food colourings.
Different substances in the mixture being analysed move at different speeds up the paper because they have different attractions to the paper (stationary phase) and the solvent (mobile phase).
Gas Chromatography (GC)
Gas chromatography is used to separate and identify substances that can be vapourised.
A mixture is heated and turned into a gas.
The substances in the mixture move through a column at different speeds, so they separate.
- Mobile phase: inert gas
- Stationary phase: liquid on a solid inside the column
Retention time: time taken for a substance to pass through the column . This (value) is used to identify the individual components in the mixture.
Here MACHEMGUY gives a very thorough and clear explanation of how GC works.
High performance liquid chromatography ( HPLC)
Watch this video to see how the retention times can be to identify the components in a mixture and how the areas of the peaks produced by the instrument can be used to determine the relative concentrations of each component.