Question

What is the effect of changing the mobile phase's polarity on a column chromatography compared to a thin layer chromatography? could you tell from the TLC on the effect on the seperation from column chromatography?

Answer 1

Note that the more polar the solvent, the faster compounds elute, regardless of the compounds polarity. This means changing the solvent polarity cannot change the order compounds elute from a TLC or column. This may seem non intuitive, as it would seem that a polar solvent would move a polar compound farther than a nonpolar compound.
To help visualize this concept, consider that solvents will compete with compounds for sites on the stationary phase. A less polar solvent will not compete well, allowing the compounds to remain bound to the stationary phase, resulting in slow elution. A polar solvent will compete well with molecules and will occupy sites on the stationary phase. This will force compounds into the mobile phase, and result in faster elution/increased travel distance.