Question

4. (6 pts) A researcher has extracted malvidin 3-glucoside from grape skins and wishes to ensure that the sample is pure by performing column chromatography. The researcher uses a silica column and 90% ethyl acetate in hexanes for the chromatography system and observes that the colored band at the top of the column does not move significantly as the mobile phase flows. Suggest why the sample is not moving on the column and what the researcher might try in order to speed up the motion of the compound on the column. Structure of malvidin 3-elucoside OH HO. HO -OH OH OH OH 0

Answer 1

The sample exists in salt form which is highly polar ( it behaves as ionic compound) and hence it retains in the mobile phase due to very strong intermolecular forces of attraction and is not movable.

To speed up, choose a highly polar solvent in which the compound is more soluble and runs faster. Dichloromethane and methanol mixture is a suitable solvent system.