Three types of chromatography are routinely used in the organic chemistry teaching labs:
1.Column Chromatography
2.Thin Layer Chromatography (TLC)
3.Gas Chromatography (GC)
In these (and all types of) chromatographies, a mixture is separated by distributing the components between a stationary phase and a mobile phase. The mixture is first placed on the stationary phase (a solid or a liquid) and then the mobile phase (a gas or a liquid) is allowed to pass through the system.
1. Column chromatography:
The stationary phase is a powdered adsorbent which is placed in a vertical glass column. The mixture to be analysed is loaded on top of this column. The mobile phase is a solvent poured on top of the loaded column. The solvent flows down the column, causing the components of the mixture to distribute between the powdered adsorbent and the solvent, thus (hopefully) separating the components of the mixture so that as the solvent flows out of the bottom of the column, some components elute with early collections and other components elute with late fractions.
2. Thin Layer Chromatorgraphy:
The stationary phase is a powdered adorbent which is fixed to a aluminum, glass, or plastic plate. The mixture to be analyzed is loaded near the bottom of the plate. The plate is placed in a reservoir of solvent so that only the bottom of the plate is submerged. This solvent is the mobile phase; it moves up the plate causing the components of the mixture to distribute between the adsorbent on the plate and the moving solvent, thus separating the components of the mixture so that the components are separated into separate "spots" appearing from the bottom to the top of the plate.
2. Gas Chromatography:
The stationary phase is a high-boiling liquid. (Think of it as a viscous oil, or waxy substance.) This high-boiliing liquid is packed into a long, narrow glass or metal column. The mixture to be analyzed is loaded by syringe into the beginning of this column. The mobile phase is an inert gas which continuously flows through the column. The components of the mixture distribute between the stationary high-boiling liquid (these components are either condensed or absorbed on the high-boiling liquid) and mobile gas (vapor) phase moving through the column. The gaseous mixture flows through a detector at the end of the column and if it has been successfully separated, the components show as different 'blips' or peaks on a recorder.
