Understanding Silica Gel Column Chromatography Desiccant Better

Definition of Column Chromatography

One of the oldest methods in practice to separate mixtures, whose different components adsorb at different levels, is column chromatography. In the column chromatography process, the compound  that has to be separated is passed through a vertical column containing a stationary as well as mobile phase. The stationary phase is the solid desiccants like silica gel and aluminium oxide. As the compound moves through the vertical (usually glass) column, components get adsorbed at their designated levels. At the end of the chromatography process, all we need to do is collect the isolated elements and continue with the individual research.

Principle of Column chromatography

The division of components by adsorption at different levels depends on two factors- 1) activity of the adsorbent used like Silica Gel, Alumina and 2) the polarity of the solvent. There can be two scenarios in this case. First, when the solvent's polarity is low and the adsorbent is quite strong and powerful. In such a situation, the separation results will be far from satisfactory.  In the second case,  both the polarity of the solvent used and activity of the adsorbent are equally high. This also will not yield the desired results. There will be incorrect results of compound separation if the second scenario occurs. The lesson we can take away from these experiments is that the separation and isolation of constituents is not always perfect and generate the desired outcome.

Silica gel column chromatography 

The most popular chromatography desiccant used in the purification industry nowadays is Silica Gel. Column chromatography using Silica Gel makes use of a glass column with the chromatography desiccant covering one-third of its length. Next, the tube is inserted into the designated solvent. At this point one must make sure that there are no air bubbles in the tube. As the mixture, which has to be purified passes through the column the component with lesser polarity will suck up first. Then comes the next constituent and the process continues till the separation is completed. 

What is Silica Gel Mainly Used to Separate?

This polar chromatography adsorbent is little acidic and hence will mostly adsorb basic components rather than a basic one. Silica Gel adsorbent finds use in the breakup and purification of substances like steroids, lipids, amino acids, dyes, alkaloids, phenolic compound and pharmaceutical intermediates. This chromatography desiccant has also displayed immobility for labile compounds, thus qualifying it to conduct all types of column chromatography.