Chromatography Forum

I have a question. When you first use a column with ion pair reagents, I realise that it never becomes the same again. You should work after with acid ion pair or basic ion pair. Is there any wahsing method that solves this problem?

A mix of methanol and 25 mM sodium dihydrogen phosphate is as good a choice as any. The methanol displaces the hydrophobic part of the IP additive and the buffer provides counterions for the charged part.

The catch is that there is no guarantee: the amine and ammonium IP reagents can stick tightly to silanols, while things like the alkyl sulfonates can contain long-chain impurities which are sufficiently hydrophobic to be difficult to remove from the bonded phase. My mantra is "columns are cheap; my time is valuable"; I'd rather dedicate columns than waste time on something that may or may not work and risk the consequences if it doesn't.

and I would rather use a column where ion-pairing reagent is attached to the surface...like in mixed-mode chromatography. Primesep is equivalent of combination RP column+IP reagent. In case of MM you don't need to worry about residual memory of the column related to IP reagent

thank you both. And tom, dedicating columns and buying others is what we do in our lab. We think equal.