Hi, I have been doing some ion pairing chromatography, with TBA (tributylamine). Seems now that when i measure in ESI+ there is a huge background of TBA (m/z 186.2) and i can't get it out of the UPLC. Does anyone have experience with this compound on how to flush it out of your system? Any suggestion is welcome!
Cheers, Geert.
Good morning Geert! To get rid of TBA I recommend you flushing your UPLC with a solution of 0.1 % TFA or 1 % FA. We do this regularly (once in a week) with our preparative HPLC system. This system works under alkaline conditions and all kinds of amines used by our chemists (e.g. HATU, DIPEA, TEA ...) are annoying because they produce a high background in the TIC trace. After flushing the system under acidic conditions (1h) the background has been decreased more than three orders of magnitude. That's only a temporary solution but it works. Greetings Markus
Ohhh, no, no, no. Do NOT use TFA!!! You will completely (and irreversibly) kill your negative ion response. Formic acid works fine. Markus is correct; the acidic flush helps. It takes a while to get rid of the TBA. Make sure you change your rough pump oil and give everything a really good cleaning with FA in methanol.
Hi All,
thanks for your comments. I have tried 30% phosphoric acid (advise from Waters), even flushed overnight with that, but no way to get it out. TFA did not help either, nor does 0.1% Formic acid. Mark, the TBA is not contaminating the MS part, it is only the UPLC part, i am almost sure that it is in the pumps, since i shortcut all parts to the MS and when i connected the flow from just after the solvent mixer (binary pump) the signal was as high as when i include the sample and/or column manager. I will give it another try flushing overnight with 1% Formic acid, but should there not also be some organic in there because of the butyl groups?.
Hi Geert, I'm sorry to hear that acidic flushing doesn't help, but maybe I have an ultimate remedy. Disconnect your column and the MS part. Then flush your system with 6M HNO3 (~ 30%). I cross my fingers.
if you have a peak, it means that TBA comes from the LC line, so disconnect the ESI source and use a mild copper solution 0.0001% and run it for 48h at low flow, nothing bind TBA TEA TMA better than Cu. Lambda 560/590 nm. One you are done with the wash rinse the line with milliq water for 48h.
In case TBA is in the background noise, I migh end up it comes from the source. in this case, I would suggest to polish each surface with alumina thin powder. Amines complex superficial metal cations and are subsequently released under the effect of the spray voltage. They are persistent contaminants because the spray voltage can sputter them almost on every metal surface.
Andrea Carra that is a brilliant suggestion! Has anyone here tried this and can they share their observations?
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