column chromatography [L, columna + Gk, chroma, color, graphein, to record] , the process of separating and analyzing a group of substances according to the differences in their absorption affinities for a given absorbent as evidenced by pigments deposited during filtration through the same absorbent contained in a glass cylinder or tube. The substances are dissolved in a liquid that is passed through the absorbent. The absorbates move down the column at different rates and leave behind a band of pigments that is subsequently washed with a pure solvent to develop discrete pigmented bands that constitute a chromatograph. The cylinder of absorbent is then pushed from the tube, and the individual bands are either separated with a knife or further diluted with the pure solvent and collected in the bottom of the tube for analysis. Effective column chromatography depends on the selection of the appropriate absorbent and solvent and a flow rate that is slow enough to allow complete diffusion of the absorbates from the solvent to the absorbent and the slowing of the absorbates according to their different affinities for the absorbent. Compare gas chromatography, ion exchange chromatography.
