Has anyone seen a 114 adduct in ESI(-)? I am having a hard time figuring out what could form this. The mobile phase contains methanol and NH4COOH/HCOOH. The standard was sent to us in denatured ethanol.

Thanks

Is there any chance you have some residual TFA in your system? I have seen TFA adducts before (114).

Thanks for the idea. I checked, and it has been a couple months since TFA has been run on the system, though, and it has never been used on the column.

TFA will stick forever in a vacuum degasser if you have one. On my system, I usually segregate 2 channels for TFA only and the other 2 for other mobile phases. Of course, same for columns, but you said that your column had never seen TFA.

Another hand up for 114 adducts being TFA in ESI-.

We use a number of water-acetonitrile LC-MS methods which employ TFA, and it's been a considerable length of time since I could use the mass spectrometer for a sample infusion (usually in a solvent mix of H2O/ACN or H2O/MeOH) in negative-ion mode and not see peaks at m/z 113, 227 [M-H]-, [2M-H]- etc... often the base peak is due to TFA, which may not have been through the LC in a week!

Anonymous (Mar 23) mentions TFA can hang around in a vacuum degasser (the system is a Waters 2795), but where does it manage to hide in the mass spectrometer? We disconnect the LC from the MS, and perform infusion from a microlitre syringe via a length of silica capillary... the capillary and MS probe are flushed a number of times before introducing a sample, typically with the solvent used to prepare the sample. The spectrometer is a Micromass ZMD4000.

If anyone has suggestions for evicting TFA from the entire system that would be greatly appreciated!