Chromatography Forum

I am working with a mixed mode strong cationic exchange and reversed phase sorbent to remove unwanted (various mostly basic) interferences. The substance I want to analyze is retained by reversed phase mechanism only. In order to achieve a very clean eluate I have started to play with basified washing steps, before locking the interferences to the sorbent by 2% formic acid. I have two questions:

1) Does basified washing steps (0.1M NaOH) reduce the efficiency of the resin to bind the interfering substances when washing with 2% Formic acid? Maybe Na+ would interfere with ion exchange?

2) I have to acidify the sample with H3PO4 before loading (release analyte from proteins). Basifyfing the sample increases viscosity, so that is not an option. Would do you thing, will the shift low pH-high pH-low pH work?


Regards,
AK

1) Does basified washing steps (0.1M NaOH) reduce the efficiency of the resin to bind the interfering substances when washing with 2% Formic acid? Maybe Na+ would interfere with ion exchange?

Probably not, but if it's a concern, you could use LiOH instead (Li+ is the most weakly bound of common cations).

2) I have to acidify the sample with H3PO4 before loading (release analyte from proteins). Basifyfing the sample increases viscosity, so that is not an option. Would do you thing, will the shift low pH-high pH-low pH work?

Without knowing any details about what you are doing, it's impossible to tell.

Without knowing any details about what you are doing, it's impossible to tell.

Well. I am simply wonder if the resins can handle pH switching without loosing efficiency. The cartridge is an Waters MCX.