CHROMATOGRAPHIC ADSORDENTS

SILICA GEL

Silica Gel is one of the most widely used chromatographic adsorbents. It is available commercially in a wide range of forms and there are numerous references in the literature to its application in chromatography. Its unsurpassed capacity for both linear and non-linear iso-thermal separations and above all its almost complete inertness towards labile compounds make it a logical first choice as a general purpose adsorbent for column chromatography.

Silica Gel may be regarded as a typical polar sorbent. The relative adsorptivity of different molecular groups or substitutes on silica gel is similar to that observed for other polar adsorbents. The silica gel surface is weakly acidic and there is a tendency towards preferential adsorption of strongly basic substances relative to adsorption on neutral or basic adsorbent. It also finds application in reversed phase partition chromatography. This adsorbent with empirical formula SiO2.xH20 is described variously in literature as silica, silica gel, silicic acid and these terms are essentially synonymous.

Application:- In the separation and purification of steroids, lipids amino acids, dyes, alkaloids, phenolic compounds and pharmaceutical intermediates.

Note:- Silica gels for column chromatography are available in any desired particle size for pilot-plant or plant applications.

SILICA GEL FOR COLUMN CHROMATOGRAPHY

Column Chromatography is today one of the most important and widely used techniques available for the separation and analyses of complex organic mixtures. The original technique has undergone a number of innovations and modifications as regards the nature of adsorbent, techniques of loading and elution etc.

The rapid spread of column chromatography to a wide variety of applications both analytical and preparative, reflects rare combinations of characteristics from these two fields, versatility, exceptional performance and marked simplicity of techniques, apparatus and interpretation.

The purification of chemical substance either naturally occuring or synthetically prepared mainly involves its separation from other chemicals present in the mixture. It is here that the high degree of efficiency of column chromatographic techniques in separating different compound classes, can be effectively made use of.

In its classical form, column chromatography consists in separating the individual components of a mixture by loading the mixture into a column packed with finely powdered adsorbent and then developing the column with a solvent i.e. eluting the individual substance in the mixture by passing a solvent or a mixture of solvents through the column. The individual substances are collected as successive eluent fractions.