Why do ten molecules of toluene that enter a GC column at exactly the same time not reach the detector at the same time? Why are London Dispersion forces of the sample molecules strongly influencing GC measurements? And why are they negligible in TLC experiments on silica gel? I have no idea how to answer the first question. The second question I'm thinking deals with the fact that the stationary phase in TLC, silica gel is polar, while the stationary phase in GC is relatively non polar. So in GC there are more weak interactions, nonpolar to nonpolar and in TLC there are stronger interactions, polar-polar aka dipole-dipole interactions.