Effectiveness of Acetic Acid for Ion Pairing

[Jimi]

Hey All

I want to ask about the effectiveness of Acetic Acid as an ion pairing agent: for proteins or for small molecules with a positive charge.

My sense is that acetic acid (or to be more precise, the acetate ion) does pair, though not as well as something like TFA. And, as a result, one needs to use a higher concentration. But that ultimately it will work, just at a higher concentration.

Please let me know what your experience has been. And what concentration levels have you found to be necessary.

Thank You

[Vlad Orlovsky]

Ion-pairing properties of TFA are overrated. It forms a "pair" but it is not increasing retention of small basic molecules and retention increase for peptides is not that great either. In my opinion you need to go to at least C4 to see any effect on retention