Is there a method for the separation of Zwitterions on Atlantis PREMIER BEH C18 AX? - WKB114573

ENVIRONMENT

• Zwitterions
• Atlantis PREMIER C18 AX

ANSWER

With quaternary amines and sulfates/phosphates, it is almost impossible to suppress ionization of these strong groups. If there are basic and acidic groups ionized, the compound becomes much more polar and might require the use of HILIC columns. If the molecule is hydrophobic enough, it might be analyzed by RP. Being able to turn on or off the ionizable group is the best approach for this phase; trying to promote anion exchange for small polar acids would be desired. We have an example of manipulating the retention of AMP across pH in the application note 720006742en (see attachment), because this molecule has two acidic pkas and a basic pka. As for primary amines, when ionized they would be repulsed on this chemistry, so retention would be challenging. Depending on the molecules' pka, if they can be neutralized (operating at elevated pH), this phase could work (operating in the pH 8-10 range).

Another alternative could be cationic exchange. It would be a good approach when the bases are charged. The HSS C18SB stationary phase may provide some benefits for these types of molecules at low pH. This is an example comparing this phase with other HSS C18 bonded phases. The SB stands for selectivity for bases (not stable bond), and it's an unendcapped T3, so there are more residual silanols, which provide some additional retention/selectivity for ionized bases.

ADDITIONAL INFORMATION