Sunday, September 12, 2010

Chromatography is Just a Metaphor for Stains and Skid Marks

Chromatography once meant "color writing" but now it's just an analytical tool in chemistry.   Chromatography started out with scientists dipping paper in solutions of crushed plant juices.  Capillary action drew the solutions up the paper--just like the quicker-picker upper Bounty paper towel does.  Things in the solution-called analytes- lag behind the wetness line creeping up the paper.  You may have even seen this phenomenon if you've ever found an old paper coffee filter with annular stain rings.
Anyway, the phenomenon gets interesting if there are two or more colored substances in the solution which form two separate rings. In theory you can dry the filter and cut the paper up, isolating the two substances.  Voilà, chromatography!

In paper chromatography, the paper is what's called a stationary phase and the water is the mobile phase. Analytes flit between the two phases to different extents-whence the separation.  Nowadays there are a ton of different chromatographies--column chromatography, thin layer chromatography, high pressure chromatography, gas chromatography, chiral chromatography--but they all rely on similar principles.


  1. What a hell of a title.

    I remember when in an assaying procedures class the new young hotshot carbohydrate biochemist when on and on about the new GCMS machine we were able to use.

    I don't blame him. Lord, was that a cool advance to the state of the field.

  2. Oh GC-MS is truly remarkable. As an analytical tool I think only fluorescent dyes do more remarkable things.