Chromatography Forum

Hello,

Does anyone have experience removing or otherwise dealing with impurities from ion pairing agents used in chromatography?

I'm using cetrimonium bromide (CTAB) with a C18 column. As organic composition increases, several impurities elute. The impurities in CTAB accumulate onto the column from the mobile phase at high aqueous composition and appear as peaks as organic composition increases.

I'm purchasing the highest purity CTAB I could find but I don't know how pure it will be.

Thanks,

Better/worse/same if the organic phase is allowed to be more minutes at the end of the run to wash such stuff off the column, before the re-equilibration step ?

Go through the link provided below... You might get good inputs on your query..

http://www.chromatographyonline.com/rea ... st-peaks-0

This is one of the reasons why ion-pair reagents and gradients are not not a happy combination. Aside from getting the highest purity material as you plan, the only other suggestion is to keep the pre-gradient equilibration time between injections constant so the impurities will be consistent from run to run, and tweak the conditions so the impurities don't interfere (yeah, right!).

Mixed-mode columns where IP is attached to the surface is always an option. No need for extensive equilibration, all methods can be MS-compatible and there is no need to dedicate either column or system for ion-pairing reagent use. We have columns with basic IP attached to the surface (Coresep SB, Heritage MA). What kind of acids you are trying to separate?