How does thin layer chromatography work?
The other commonly used stationary phase is alumina – aluminium oxide. The aluminium atoms on the surface of this also have -OH groups attached. Anything we say about silica gel therefore applies equally to alumina. What separates the compounds as a chromatogram develops? As the solvent begins to soak up the plate, it first dissolves the compounds in the spot that you have put on the base line. The compounds present will then tend to get carried up the chromatography plate as the solvent continues to move upwards. How fast the compounds get carried up the plate depends on two things: • How soluble the compound is in the solvent. This will depend on how much attraction there is between the molecules of the compound and those of the solvent. • How much the compound sticks to the stationary phase – the silica get, for example. This will depend on how much attraction there is between the molecules of the compound and the silica gel. Suppose the original spot contained two compounds – one o
