In: Chemistry
Thin Layer Chromatography (TLC) uses a thin film of silica gel as the stationary phase, ~Si(OH)2 O ~ units. While the mobile phase is designed to be more polar than silica gel, drives the compound within the sample to separate and become distributed across the surface of the stationary phase through capillary wetting.
If the compound is pure, one spot will develop; if it is not pure and a mixture of two or more compounds, separate spots will appear for each compound in the mixture. At least that is the idea. Beacause sometimes it is difficult to get a clean separation between compounds of very similar chemical makeup. After that the polarity of the mobile phase is then adjusted and the experiment is repeated with a new plate. In this way there are more analytical forms of chromatography that have very high resolution compared to tlc.
So these are the reasons due to which mobile is more used than tlc.