Column Chromatography - basics

A day in the life of a synthetic organic chemist.

Column chromatography is a separation method based on the same principles as thin-layer chromatography; see my previous video on this subject for more information: http://www.youtube.com/watch?v=1rt25dy_hxw

Note that unlike TLC, column chromatography is not an analytical method, but a preparatory one; not qualitative but quantitative. You use it to purify a mixture, not determine what it's composed of. Nonetheless, column chromatography is practically always accompanied by TLC'ing the fractions to determine the compounds in them and therefore, their composition and purity.

The method employs a gel of a stationary phase in an eluent through which the compounds in a mixture may pass at variable speed. They are pulled through the solids by use of more eluent sitting on top of the stationary phase, with the polarity and properties of the eluent designed around separating any impurities as well as possible from your target compound. The eluent (with any compounds in solution) drips out at the tap at the bottom of the column and this is collected in small containers as fractions of the column. This allows you to test all the fractions for which compounds are in them, and when you know this, you can take the fractions which contain ONLY your product and discard and that contain impurities. Combination of these pure fractions and consecutive removal of the solvent will then yield your product in a pure fashion.

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• synthetic
• organic
• chemistry
• column
• chromatography
• TLC
• thin
• layer
• reaction
• mixtures
• impurities
• preparatory

[jjacobs126]

Do you have advice on separating carboxylic acids? I am currently working with a compound that is a dicarboxylic acid and I have a really hard time getting it through the Silica. Any advice?

[ElsjeMay]

Loving the voice :p