Question

4. How is the eluent polarity changing when the solvent is switched from 100% hexanes to 1:1 hexanes : ethyl acetate? What is the purpose of this switch?

Answer 1

Eluent is the solvent which helps to elute the desired/separtaed product from column or chromatographic column.

There are two kinds of eluents non-polar (which elute non-polar substances with them) and polar (which elute polar substance with them).

100% Hexene is non-polar solvent and hence it elutes non-polar substance.

When it is converted to 1:1 Hexane : ethyl acetate it becomes 50%:50% HExane : Ethyl acetate.

SO now eluent (Mobile phase solvent) contains half amount of polar solvent along with half amount non-polar solvent. so some amount of mixture of polar and non-polar substances will be eluted with this mixture.

In totality, Eluent will become more polar.

Purpose of this switch is to elute more polar substance or separate two closely present polar sunstance. 100% Hexane alone can not used as eluent to elute polar substances.