A chromatographic method in which the components of mixtures are separated according to their different partition coefficients. Any substance dissolved, at a given temperature, in two immiscible solvents has, at equilibrium, a certain characteristic proportion dissolved in each solvent. The ratio of the amount of solute in one solvent to that in the other is the partition coefficient. In column partition chromatography the column contains some hydrophilic substance, e.g. silica or starch granules. Water is tightly bound to the surface of the granules and acts as the stationary phase. A solvent immiscible with water, e.g. butanol or phenol, and carrying the mixture to be separated is then passed through the column. This is the mobile phase. Those components of the mixture that are more soluble in water will pass through the column more slowly than those that are less soluble in water but more soluble in the mobile phase. The components are separated by collecting and analysing small amounts of the eluate (the liquid passing from the bottom of the column) as it emerges from the column. Mixtures of amino acids are often separated in this way. * Paper chromatography is a particular kind of partition chromatography in which the hydrophilic cellulose of the paper holds the water and acts as the stationary phase. |
