is there a general rule of thumb when to use SCX/SAX or WCX/WAX Columns ? (Im working with proteins/peptides).
With proteins it is hard to have a "general rule" about anything, but we can borrow a rule from solid phase extraction: if you are working with strong acids or bases as analytes, choose a "weak" ion exchange resin. If you have weak acids or bases, choose a strong ion exchange resin.
The reason we do this is that if you combined the strong acid/base with a strong ion exchange resin, the interactions would be so strong that the analytes might never come off.
Similarly, the weak-weak combination might not provide enough interacation.
I would start with a WCX/WAX, just to be safe.
thx for your answer,
so this means that peptides can be seen as "weak bases/acids" and proteins are "strong bases/acids"
--> the larger the peptide or protein the higher the probability that it behaves like a "strong base/acid" ?
(due to the higher amount of charged amino acids ) ?
I am not sure I want to make such a general statement. Yes, the number of charges will make a difference, but the type of charge (strong/weak acid/base) should also be considered. However, starting with a weak exchanger is a safe approach, and you can always try something different if you do not get the proper interactions.
ok, thx for your answer !