CHROMATOGRAPHIC TECHNIQUES



CHROMATOGRAPHIC TECHNIQUES

A brief description on the historical development of the main techniques is listed below:

1:    PAPER CHROMATOGRAPHY

In this method, the dissolved substances are applied as a small spot on a cellulose bound filter paper which is then kept in a container dipped in an organic solvent. The mixture are partitioned between paper (Stationary phase) and organic solvent (mobile phase).

2:     PARTITION COLUMN CHROMATOGRAPHY

In this method, the column is packed with a porous solid of high surface area e.g. silica gel and cellulose which is coated with water (stationary phase). The components of a mixture arc separated by passing an organic solvent (mobile phase) through the column.

3:     ION EXCHANGE CHROMATOGRAPHY

Ionised compounds are separated in aqueous solutions (mobile phase) by virtue of their differences in affinity for ionised compounds which are an integral action of the insoluble solid phase (stationary phase).

4:     THIN LAYER CHROMATOGRAPHY

In this method, the adsorbent (stationary phase) is spread over a glass plate in a thin film of even thickness. The. solvent (mobile phase) moves up the plate by capillary action and.thus affects separation.

5:     GEL FILTRATION

Sephadex contains the aqueous (stationary phase) which is distinguished from the mobile phase by, its immobilization. The components of the mixture are separated according to their size by virtue of the differential distribution between easily displaceable water present in the interbcd space.

6:     GAS LIQUID CHROMATOGRAPHY

A column is packed with a porous inert solid coated with a thin layer of an involatile liquid as the stationary phase. Components of the mixture are separated by being partitioned between this phase and a gaseous (mobile.phase).

7:     ADSORPTION COLUMN CHROMATOGRAPHY

In this method, the separation of a mixture is determined by the differential adsorption of the components on an active solid (alumina, silica gel, stationary phase) as an organic solvent (mobile phase) containing them which passes over and affects separation.

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