Chromatography Forum

Dear all,
we have an inquiry for the purification of an API. This will be done with an Ammonium buffer in the mobile phase, but after purification the counter ion has to be replaced by Sodium (I'm not allowed to provide any details about the type of sample, because of the secrecy agreement)
We never have done this, but I guess this can be done by ion chromatography(?). My question is, how can I test, if really all NH4 is replaced? Also by ion chromatography?

Thanks for all answers

Wolfgang Schräder

If your compound is stable I would just add sodium hydroxide in portions while heating solution of your API in aqueous solution. You can also aerate you solution to help ammonia escape.
You just need to shift equilibria towards formation of sodium salt by removing ammonia from solution

Thank you for this suggestion.
As the substance is heat sensitive, I will try to aerate the solution. However still the second question remains, how can I test, if the Ammonium has been removed completely?

Wolfgang Schräder

if the Ammonium has been removed completely

How completely? 95%, 99%, 99.9% ??? Are there any other nitrogen atoms on the molecule? (if not, it may be as simple as sending a sample out for CHN analysis).