For University of Illinois chemistry professor William Pirkle, chromatography is like a soap-opera wedding. Imagine, he says, a happy couple who stop and talk to well-wishers standing on the church steps before leaving for their honeymoon. One of the newlyweds encounters an old flame--the true love--and then parts from his or her beloved.

Alas, where there once was togetherness is now a separation. In chromatography, explains Pirkle, what separates disparate entities in a chemical mixture, such as a cell extract of thousands of proteins or a sample of water with different pollutants, is the attraction of its component members for a surer thing--a solid. Depending upon the strength of this relationship, the different parties will separate from each other at varying rates.

In chromatography parlance, a chemical mixture is dissolved in a gas or a liquid called the mobile phase, which pushes the sample through a cylindrical glass or Plexiglas...

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