Question

Discuss why different elution solvents are often used in the column chromatography. In what order and why should the elution solvents be used? In this experiment would the separation happen if only 10:90 ethyl acetate/hexanes was used as an eluting solvent? Would the separation happen if 20:80 ethyl acetate/hexanes was used first followed by 10:90 ethyl acetate/hexanes?

I need at least a paragraph response to this!

Answer 1

Different elution sovents solvents are in column chromatography because different slovent have different eluting power.

The “eluting power” of a solvent is largely a measure of how well the solvent can "pull" an analyte off the adsorbent to which it is attached.

There is a series known as Eluotropic Series which is used to determine necessary solvents needed for chromatography of chemical compounds. And, normally such a series progresses from non-polar solvents, such as n-hexane, to polar solvents such as methanol or water. The order of solvents in an eluotropic series depends on

1) the stationary phase and,

2) the compound used to determine the order.

Thus elution solvents should be used because when the eluent adsorbs onto the stationary phase, it displaces the analyte and hence pulls the analyte off from the adsorbent . Therefore, it plays a key role in separation of a mixture of compounds.

Yes, 10:90 ethyl acetate /hexane can be used as an eluting solvent for elution only when it is followed by a more polar eluting sovent.

But the 20:80 ethyl acetate/hexane followed by 10:90 ethyl acetate /hexane can't be used as eluting solvent beacuse it follows reverse/ decreasing / non progressive polarity order of eluting solvent.