Chromatography Forum

for anion exchange, i can use TFA, formic acid, acetic acid,
for cation exchange, I can use ammonium carbonate, formate, and acetate.
what is the problem using these buffer, they are very weak?
are they good for ion exchange SPE?

I've used 10 mM NH4OAc as a buffer in WCX (eluted by increasing [H]. It is "volatile" however, if you used a gradient to 0.5 M NH4OAc to elute your column, I have no idea how easy it will be to get rid of that much salt, "volatile" or not.

Honestly i prefer NaCl or LiCl in IEX followed by desalting because the complete removal of the "volatil" buffers is sometimes difficult, especially when peptides are purified. Best experiences (for voltile buffers) in terms of performance i had with ammoniumacetate/carbonate and formate based buffers. For a decent overview of used iex buffer systems in protein purification see:

http://wolfson.huji.ac.il/purification/ ... uffer.html

Anyone have details on "volatilizing" these buffers? Are repeated lyophilizations required, or, can you just put the dry stuff under a vacuum and expect it to "evaporate"?

Normally, we use double lyophilization (2x over night) but even then a acetate signal (if NH4Ac was used) will be found in 1H-NMR. Running it through a desalting column will remove counterions to a great extent (no buffer signal in nmr).
Well, I never tried to use HV line to remove the buffer, but in the end it is the same as lyophilization. The sample will freeze and sublimate over time.

but my analytes are well below 1000Da.
i will elute with buffer from desalting column.

Normally, we use double lyophilization (2x over night) but even then a acetate signal (if NH4Ac was used) will be found in 1H-NMR. Running it through a desalting column will remove counterions to a great extent (no buffer signal in nmr).
Well, I never tried to use HV line to remove the buffer, but in the end it is the same as lyophilization. The sample will freeze and sublimate over time.

Could post some details? Mw, anion exchange cation echange, analytical application, prep run would make it easier to think about the problem.