Column chromatography is an extension of thin layer chromatography (TLC). Instead of applying a sample on a thin layer of silica or alumina, a sample is deposited on a cylinder of adsorbent and solvent is continually applied with pressure until the components completely drain from the cylinder. With this modification, components can be not only separated but collected into different containers, allowing for purification of mixtures. Column chromatography (also known as "flash chromatography"), is frequently used in research settings, as is evidenced by its common occurrence in the procedural sections of journal articles.
- 2.4A: Macroscale Columns
- The same underlying principles of thin layer chromatography (TLC) apply to column chromatography. In fact, a TLC is always run before performing a column to assess the situation and determine the proper solvent ratio. There are a few variables which aren’t applicable to TLC, but which affect the separation of components in column chromatography. These include the column diameter, quantity of adsorbent used, and solvent flow rate.
- 2.4B: Microscale (Pipette) Columns
- A macroscale column is much too big for very small quantities of material (< 20 mg). Instead, a column can be constructed using a disposable Pasteur pipette.