Welcome Guest Search | Active Topics |

Tag as favorite
Liquid Chromatography Question
Options
Previous Topic Next Topic
Kiha_3659
#1 Posted : Wednesday, July 31, 2019 5:12:37 AM
Rank: Newbie

Groups: Registered
Joined: 5/5/2019
Posts: 2

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
TO whom it may concern,

I had a question regarding the LQ Chromatography Lab Techniques.

In a polar stationary silica phase, and a non-polar mobile phase,
a compound that is more polar has a lower Rf value and moves less than a nonpolar compound.

However, if we change the eluent to be more polar (ie aqueous alcohol), how will the Rf values change?

I heard that the compounds will significantly move faster up, regardless of its polarity.
Would the Rf values change (increase) than a less-polar mobile phase?
Back to top
Report?
INSTR_Katerina_102
#2 Posted : Wednesday, July 31, 2019 5:58:31 PM
Rank: Advanced Member

Groups: Registered
Joined: 6/24/2019
Posts: 250

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
Hi Kiha,

The Rf of a compound is determined by the relative "amount of time" it spends in the mobile phase vs the stationary phase.

When you make the mobile more polar, all compounds tend to have a higher Rf and travel further. This is because the compounds start spending more time in the mobile phase, as the mobile phase starts being less significantly different from the stationary phase in terms of polarity.

Likewise, Rf values are smaller as compounds travel shorter distances with a non polar eluent.

Please let me know if this is unclear.

Cheers,

Katt
Back to top
Report? | Edit by user
Users browsing this topic
Guest
Tag as favorite
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.

Clean Slate theme by Jaben Cargman (Tiny Gecko)
Powered by YAF | YAF © 2003-2009, Yet Another Forum.NET
This page was generated in 0.103 seconds.