Question

In the step gradient separation, four separate fractions were collected. How were these related to the polarities of the column and of the eluting solvent?

Answer 1

  These related to the polarities of the column and of the eluting solvent When you run a column are 
 1) always start with a more non-polar solvent ratio and SLOWLY increase the polarity of the solvent.
1) Columns are generally made with silica which is highly polar, so compounds that are more polar in nature will interact with the silica more than those that are non-polar.
 3) The first fractions to come out should be most non-polar, with each fraction collected after that being more and more polar.
hope this helps

Answer 2

Answer:

The polarity of the fraction will decrease when icreases the elution time. In other words the polarity order would be: 1>2>3>4.

Explanation:

If we use reverse chromatography as a separation method, the stationary phase would be non-polar and the mobile phase would be polar. Also, in the gradient separation process, the polarity of the mobile phase would change. We go from a high polarity to a low polarity, therefore the fractions that are eluted first would have a higher polarity than the ones that interact more with the non-polar stationary phase.

So, the polarity of first the fractions would be higher and would go down as they passed more time on the column.