chromatography

chromatography
    n 1: a process used for separating mixtures by virtue of
         differences in absorbency
    

Chromatography \Chro`ma*tog"ra*phy\, n. [Gr. ?, ?, color +
   -graphy.]
   1. A treatise on colors [archaic]
      [1913 Webster]

   2. (Chem.) an analytical and preparative technique for
      separating substances by differences in their selective
      adsorption to solids, by passing a liquid over the solid,
      to which the substances to be separated have usually been
      adsorbed in a preliminary step. The major variations are
      column chromatography, in which the substances to be
      separated are adsorbed to a column with any of a wide
      variety of adsorbing solids in powdered or granulated
      form; paper chromatography, in which the solids are
      applied as a spot at one end of a strip of absorbent paper
      (such as filter paper), and the liquid is percolated
      through the paper by capillary action; and thin-layer
      chromatography (TLC), which is similar to paper
      chromatography, but the adsorbent material is, instead of
      paper, a thin layer of finely powdered material, such as
      cellulose or silica, on a backing of glass or plastic,
      called a TLC plate. A modern version of {column
      chromatography} is high-performance liquid chromatography,
      usually referred to as HPLC.
      [PJC]