Chromatography Forum

Intense positive ions m/z 102 and 239 show up in reversed-phase LC/ESI MS, don't know where they come from. They were observed before (after washing with organic solvent, normally will be decreased significantly), but get pretty intense since yesterday. In our usage, different mobile phases are used including ACN, MeOH, H2O, ammonia formate/acetate, triethylamine. I used fresh ACN, MeOH to wash for pretty long time, no help. Changed some connection tubings and cleaned the ESI source, no help either. Your advice is greatly appreciated.

What is your column?

Most possibly it is not due to the column since I took the column off, these two ions are still there.

James,

102 is from triethylamine and once you have used a column that contains triethylamine is not very easy to get rid of it. Here is an article below for your reference... Good luck!


Rutters H, Mohring T, Rullkotter J, et al.
The persistent memory effect of triethylamine in the analysis of phospholipids by liquid chromatography/mass spectrometry
RAPID COMMUNICATIONS IN MASS SPECTROMETRY 14 (2): 122-123 2000

Thanks a lot, Kostas. This perfectly explains my case since I also use ion trap MS.

Now have to clean this out. The paper shows very extensive work. Some of my research need the basic additives. Since TEA is not good at all according to this manner, I am considering hexylamide, which is also good for my separation and does not see much significant ion suppression. Wonder if you happen to know if hexylamide also has such "memory effect". Again, great thanks.

Do you really mean hexylamide or hexylamine? I have used hexylamine with better success in triple quadrupole instruments so it should be better with ion traps as well. The m/z is also 102 so you'll better use a column that hasn't seen triethylamine before, otherwise you might end up to the same conclusions.

If you end up trying it, let me/us know how it worked with an ion-trap instrument.