Surface Activity:

In surface activity, it is the property of adsorption that is mostly used for separation. The methods could be chromatographic and non-chromatographic. The chromatographic technique is as follows:

• Liquid-solid adsorption chromatography
• Gas-solid adsorption chromatography

In liquid-solid adsorption chromatography the active adsorbent acts as a stationary phase and the liquid as a mobile phase. The stationary phase could be in the form of a column or a thin layer on a glass plate. Paper chromatography cannot be exclusively categorized as liquid-liquid partition chromatography. It will be justified to put it under the head of adsorption chromatography if the cellulose of the paper is playing an active role as an adsorbent. The high pressure/ high performance versions of adsorption chromatography both on column and thin layer are in use.

In gas-solid adsorption chromatography, the carrier gas along with the volatile components of the mixture flows over an active adsorbent packed within the column. Because of differences in adsorption affinity of the elements, the segregation of the elements takes place. As compared to gas-liquid chromatography in that a liquid is coated over an inert material packed within the column, here in gas solid chromatography, an adsorbent is crammed.