MIGRATION PHENOMENON

The eluent moves up through the stationary phase, mainly by capillary action.

MIGRATION SPEED

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.

The interactions involved are weak, mainly electrostatic interactions between dipoles, and specific possible interactions such as hydrogen bonds.

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.