ion pair chromatography

[qfiviera]

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?

[tom jupille]

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.

[Vlad Orlovsky]

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

[qfiviera]

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