Question

Chromatography is used in many different ways in the workplace to analyze medical, environmental, and industrial samples, for example. How does it accomplish this in terms of physical and chemical interactions?

Answer 1

Understand that all chromatographic techniques use a stationary phase and a mobile phase. The stationary phase is commonly made up of silica or alumina. The mobile phase is a solvent and it should be selected with respect to the compounds to be seperated or identified.

I shall use silica as the stationary phase. Silica is a lattice with -OH groups. This makes the silica polar. Thus when a compound mixture is added to, say a column chromatograph, the more polar compound is adsorbed more into the stationary phase than the less polar (or non-polar) one.

Then the mobile phase is less polar (non-polar) when compared to the stationary phase. It desorbs the less polar (non-polar) compound and pushes it down the column.

Hence, the less polar (non-polar) compound travels faster in the coulmn than the less polar one. This seperates the two compounds in a mixture. This is the basic physical and chemical mechanism which lies behind all chromatographic techniques.