[John]

Im doing a Column Chromatography: Separation and Purification of Fluorene and Fluorenone in lab. Ive been asked the following question.

Hexane is the first solvent, and dichloromethane is the second solvent used for the separation of fluorene and fluorenone.  Why would it be unwise to use dichloromethane first?  What would happen?

I know that hexane is the least polar eluant (solvent) but I dont now what difference it makes which goes in first? Don’t fully understand the mechanics of this procedure…I’ve never done, or seen it!

[Smrt guy]

The idea of using a less polar solvent first is to elute the less polar component (or at least get significant separation) first before switching to the more polar solvent.  If you start with the more polar solvent you will elute the two components together (i.e. you will not get a separation).

[John]

OK...Thanks for the info! I've never seen this done so its a bit tricky to visualize.