Chromatography Forum

Hi,
I have some questions about the advantages to use heptafluorobutiric acid or perfluoroheptanoic acid instead of TFA in LC/MS (+ESI).
There are significant differences between these reagents regarding ion pairing effect / volatility / ion supression ?
The same for Ammonium TFA versus TFA
Thank you!

Check out:

J Chromatogr A, 937 (2001), 41-47

That paper addresses signal suppression more than chromatography. HFBA and perfluoroheptanoic acid were found to suppress signal more than TFA.

In addition of what MG said and assuming that you do not ask the difference of these ion-pairing reagents in terms of chromatography, all the ion-pairing reagents you mentioned are more volatile in their acid form than the salt form. Actually only TFA can be used in the salt form in low concentrations, all the other are not volatile in the salt form.

For more information see:

http://lcgceurope.adv100.com/lcgceurope ... sp?id=9090

Now in terms of ion-suppression, I have done some work of my own and at least for the analytes and conditions I used I didn't see more ion-suppression for higher chain length ion-pairing reagent than TFA (although it could make some sense from a theoretical point of view).