Chromatography involves any laboratory technique used to
separate a mixture into its fundamental components. The mixture is first
dissolved in a fluid (gas or liquid). This is called the mobile phase. This
fluid then goes through a structure called the stationary phase. The stationary
phase has certain properties that facilitate the separation of the mixture in
the fluid phase. As the fluid phase travels through the stationary phase,
differential partitioning causes the constituents to travel at different
speeds, thus causing the separation.
Chromatography serves two main purposes in a lab
environment: preparative or analytical. Preparative chromatography is a form of
purification in that it separates the components for a more advanced use. For
example, a chromatography technique might be used to separate DNA from the
other components of a cell in order to perform further analysis on a sample of
pure DNA. Analytical chromatography serves to demonstrate the relative
proportions of components in a mixture. A lot of times, a single chromatography
procedure will be both preparative and analytical.