A technique used to separate and identify the components of mixtures of similar compounds, such as different amino acids or chlorophyll pigments, by selective adsorption. The mixture, dissolved in a liquid or gas mobile phase is passed through another solid or liquid medium the stationary phase. This may be, for example, a column of charged resin (see ion-exchange chromatography ) or a piece of filter paper (see paper chromatography). Some of the compounds in the mixture will pass more slowly through the stationary phase than others, as they are more strongly adsorbed by the solid, or more soluble in the liquid. Consequently, the mixture will separate out. The column, strip of paper, or other material containing the separated components is termed a chromatogram. In some techniques, the compounds are collected as they emerge from the column, or their progress along the column is measured against a known standard. Colourless components of the mixture can be identified by electronic detection, ninhydrin developer, or radioactive labelling. See also gas-liquid chromatography , thin-layer chromatography. |
