Chromatography.

Chromatography is applied for separation of one or more biological compounds from a mixture of such compounds. Chromatography is based on two phases of the compounds. One is the stationary phase and the other is the mobile phase. The stationary phase may be solid, gel, liquid or solid liquid mixture.

The mobile phase may be liquid or gases which flow over the stationary phase. In paper chromatography, the cellulose fibres of, the paper is the stationary phase, in thin layer cromatography, the thinly coated gel on plate is the stationary phase and in column chromatography, the packed glass or metal column acts stationary phase. The differential solubility

ability of the individual compounds in the stationary and mobile phase is the basis of separation of compounds. The specific solvents solublise the compounds and when it moves along the stationary phase it carries with it the compounds of differential solubility. The ratio of the distance travelled by the solvent and the compounds of different nature is different depending upon solubility of the compounds. The relative flow (Rf) value of a particular compound over a particular stationary phase is constant under standard condition of temperature, pH and solute concentration. By determining the Rf values the compounds can be identified. Amino acids, sugars, alkaloids, phenolic compounds, plant pigments etc. can be easily separated by chromatography.