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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: xshadow on October 09, 2021, 07:00:56 AM

Title: chromatography resolution and retention
Post by: xshadow on October 09, 2021, 07:00:56 AM

Hi, I have some ""doubts"" about the chemical-phisical meaning of the "retention" contribute that appears in resolution expression:

R_AB= efficiency + selectivity + K_B / (1+ K_B)

Where A and B are two solutes (and B elutes last)
The  K_B / (1+ K_B) is the "retention"

Now looking at its expression I can see that:

a) when K_B >> 1 the retention is K_B/K_B = 1
b) from that formula  it seems that retention goes from 0 to 1.
c) ...so in order to increase retention (and therefore resolution) I need to increase  K_B

is it correct?

Now why should a higher retention time (expressed though a higher K_B  increase resolution???
What is the analitical chemistry "reason" ?!

THANKS :)