Please help! pKa and pH Ionization Question
Hello,
Just a quick question.
I am analysing the group of 2-arylpropanoic acids which are part of the non-steroidal anti-inflammatory drugs (NSAIDs), specifically, ibuprofen, naproxen, ketoprofen, fenoprofen, suprofen and flurbiprofen.
All of these compounds have a propanoic carboxyl acid with very similar pKa's in the range ~3-4. They are being put in a mobile phase which has a pH of 6.3.
Am I right in thinking that the this will cause deprotonation and electrons to become dissociated around this functional group, as it is effectively putting something more acidic into something less acidic/more basic so this would cause them to become ionized?
Thanks for any help!
Just a quick question.
I am analysing the group of 2-arylpropanoic acids which are part of the non-steroidal anti-inflammatory drugs (NSAIDs), specifically, ibuprofen, naproxen, ketoprofen, fenoprofen, suprofen and flurbiprofen.
All of these compounds have a propanoic carboxyl acid with very similar pKa's in the range ~3-4. They are being put in a mobile phase which has a pH of 6.3.
Am I right in thinking that the this will cause deprotonation and electrons to become dissociated around this functional group, as it is effectively putting something more acidic into something less acidic/more basic so this would cause them to become ionized?
Thanks for any help!
The mobile phase always has to be chemically inert (stop it from reacting with solvent/solute) so I'm assuming it somehow stops the two interacting.
Alternatively, I think you're mixing a weak acid with a weak acid. The overall pH should change, but apart from that I think the only thing that will be affected if how much acid is dissociated. It just depends whether the mobile phase is a Bronsted-Lowry acid or base.
Alternatively, I think you're mixing a weak acid with a weak acid. The overall pH should change, but apart from that I think the only thing that will be affected if how much acid is dissociated. It just depends whether the mobile phase is a Bronsted-Lowry acid or base.
Original post by DashStrike
The mobile phase always has to be chemically inert (stop it from reacting with solvent/solute) so I'm assuming it somehow stops the two interacting.
Alternatively, I think you're mixing a weak acid with a weak acid. The overall pH should change, but apart from that I think the only thing that will be affected if how much acid is dissociated. It just depends whether the mobile phase is a Bronsted-Lowry acid or base.
Alternatively, I think you're mixing a weak acid with a weak acid. The overall pH should change, but apart from that I think the only thing that will be affected if how much acid is dissociated. It just depends whether the mobile phase is a Bronsted-Lowry acid or base.
The mobile phase used is THF / Na Citrate in a ratio 10:90.
Oooh, a salt! Buffer solution springs to my mind. When samples contain ionizable compounds, the mobile phase pH can be one of the most important variables in the control of retention in a reversed-phase HPLC (RP-HPLC) separation. However, if it is not controlled properly, pH can be a source of many problems. Since most compounds analyzed by RP-HPLC contain more acidic functional groups, most mobile phases require pH control. For this reason, buffers are widely used.
(edited 10 years ago)
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