Thick-layer chromatography is performed on a preparative scale in the same gener

Question

Thick-layer chromatography is performed on a preparative scale in the same general fashion as TLC but the plates have much thicker layers of silica or alumina. Relatively large amount of a mixture are spotted in a virtual band along the origin (many spots are placed side by sied). The plates are then developed in the usual fashion. Suppose a 75:25 mixture of A (Rf = 0.80) and B (Rf = 0.40) is run. Draw the developed chromatogram you should expect to see. How can A and B be recovered from the plate?

Explanation / Answer

This is hard to draw on here, so I'm not going to try. However, all you need to do is draw a picture of a TLC plate (just a rectangle) that is 10 cm in height. At 4 cm, put a spot on the middle of the plate, and at 8 cm put another spot above the first one. You should have 2 spots in the middle of the plate, one above the other.

To recover the compound from the plate, simply scratch off the silica gel from the plate, and extract the residue with an organic solvent which the compound is soluble in.

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