How does it work?
The eluent moves up through the stationary phase, mainly by capillary action.
Each compound of the sample moves at its own speed behind the solvent front. The speed with which the solutes move, and therefore their separation, depends on two forces:
- The forces of attraction of the adsorbent on the solutes
- and the driving forces of the eluent which tend to extract them.
Generally speaking, the stationary phase is more polar than the mobile phase (when the latter is made of organic solvents): low polarity compounds migrate faster than polar ones.