How to perform a TLC?

Mechanisms involved

The compound to be analyzed is subject to a competition between:

its adsorption on the stationary phase
its solubilization in the eluent
the adsorption of the eluent on the stationary phase

Diagram of the interactions between the compound to be eluted, the mobile phase and the stationary phase. Between the compound and the stationary phase : adsorption. Between the compound and the mobile phase : solubilization. Between the mobile and stationary phases: adsorption.

Adsorption of the eluent on the stationary phase: the solute is driven by the eluent.

Two types of forces are involved when the eluent drives the solutes by adsorption chromatography:
⇒ Dissolution: solutes tend to dissolve in the eluent and migrate with it.
In this case, it has to be effective enough to outweigh the adsorbent’s adsorption capacity.
⇒ Displacement phenomena: eluent molecules look for the same adsorption sites as solute molecules and thus displace them.