Question

During a column chromatography laboratory experiment, a column is to be run with hexane first, then a hexane/ dichloromethane mixture, then 100% dichloromethane. What will happen if you mix up the hexane and dichloromethane? How can you fix the problem?

Answer 1

The purpose adding hexane first is, since the hexane is non polar solvent, first the less polar compound of the mixture will come first

then by adding hexane/dichloromethane mixture next higher polar compound of the mixture will come out of the column

third by using 100 % dichloromethane higest polar compound of the mixture will come out.

therefore by adding hexane and dichloromethane intially will lead to mixture of compound instead of pure compounds.

To avoid this, either we can distill the hexane and dichloromethane mixture since the dichloromethane is low boiling compare to hexane it come out first, then we can use the pure hexane in the column chormatography

or we add more hexane therefore the polarity of the mixture will comedown