Effect on the results of a column chromatography?

Question

what would be the effect on the results of a column chromatography if metanol were not completely removed from the leaf extract before chromatography

Answer 1

I wonder if this question belongs more in the Chemistry section - but then again chromatography is used in the life sciencies pretty much.

Remember that chromatography separates a mixture into its components.  However, oftentimes, a very complex mixture needs to be "cleaned up" by other means prior to the actual chromatography is carried out.  Clean up can be via several means, including liquid / liquid extraction (perhaps enhanced via pH adjustment), precipitation, or other means depending upon the specific mix you have.

If the clean up does not occur, the mix may not separate.  

Remember that the separation occurs due to polarity difference among elements in the mix in most column chromatography processes.  The stationary phase (often a silica) is very polar; the elution solvent is far less polar and as solvent passes over the column, a continual absorption onto the stationary phase followed by dissolution into the liquid phase occurs.  The separation happens because some components have a higher affinity for solvent than others.

If a component that is not cleaned up beforehand is added to the column, it can greatly interfere with the absorption / desorption process that enables the separation.

This is what makes the separation complex especially when you are developing an analytical method in a complex matrix.

For your specific example, I suspect the clean up removes components that would foul the separation.