Chromatography is a technique used to separate the components of a mixture. It can be used as an analytical technique to gain information about what is present in a mixture, or as a purification technique to separate and collect the components of a mixture. 9.1: Prelude to Chromatography A mixture of ferrocene and acetylferrocene is purified with column chromatography. 9.2: Chromatography Generalities Chromatography in the organic chemistry laboratory can be classified into several broad categories: Thin-lay chromatography, Column chromatography and gas chromatography. These techniques follow the same general principles in terms of how they are able to separate mixtures, and so will be discussed collectively in this section. Details specific to each technique will then be further discussed in their own sections. 9.2A: Overview of Chromatography 9.2B: General Separation Theory 9.3: Thin Layer Chromatography (TLC) Many students enter organic chemistry having already done a form of chromatography in their academic career, either in grade school or in general chemistry. Most likely, this will have been paper chromatography (Figure 2.4), as the materials are cheap but still effective. Paper chromatography can be used to separate the dyes in pens, markers, and food coloring. Thin layer chromatography (TLC) is an extension of paper chromatography and uses a different stationary phase. 9.3A: Overview of TLC 9.3B: Uses of TLC 9.3C: The Retention Factor 9.3D: Separation Theory 9.3E: Step-by-Step Procedures for Thin Layer Chromatography 9.3F: Visualizing TLC Plates 9.4: Column Chromatography 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. 9.4A: Macroscale Columns 9.4B: Microscale (Pipette) Columns