Hello, I was doing Thin Layer Chromatography (silica gel) and I said that if you
ID: 1035100 • Letter: H
Question
Hello, I was doing Thin Layer Chromatography (silica gel) and I said that if you had spotted non-polar and polar solutes on the silica gel given a polar solvant, the non-polar solute willt travel the furthest since the polar solute will want to stay at the bottom where the stationary phase is the polar solvent. This was marked correct by my professor.
However, given the same two solutes and a non-polar solvent, my professor claimed that the non-polar solute will travel the most on the silica gel.
Why is this so? Should not the non-polar solute stick closer to the bottom since it is attracted to the non-polar solvent?
Explanation / Answer
A competition is set up between the silica gel plate and the development solvent for the spotted material. The very polar silica gel tries to hold the spot in its original place and the solvent tries to move the spot along with it as it travels up the plate.
The polar solute will have greater interaction with the silica gel than that of non-polar solute. Hence, the case.
Extra:
The outcome depends upon a balance among three polarities - that of the plate, the development solvent and the spot material. If the development solvent is polar enough, the spot will move some distance from its original location. Different components in the original spot, having different polarities, will move different distances from the original spot location and show up as separate spots.
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