I have identified carvacrol and thymol via thin-layer-chromatography and via gas chromatography On a normal silica plate the thymol has a higher Rf-value then carvacrol. The explanation for this would be the position of the hydroxyl-group and the difference size of the nearby methyl or isopropyl group. I think thymol should be more hydrophobic then carvacrol, explaining the less interaction with the silica gel resulting in a higher Rf-value.
The problem is, that the analysis by gas chromatography with a non-polar column shows a different elution profile. I would expect that thymol, according to the higher hydrophobicity, should have a higher retention time then carvacrol. This isn't the case. Carvacrol (27.08 min) elutes after thymol (26.51 min). Is there any explanation I'am not aware or is my thinking simple wrong?