m/z 240.23 contaminant?

[dkloos]

Hi there,

I am trying to get rid of a contaminant from my LC/MS system, but I figured it might help to know what it is. I could not find the mass in our common list of contaminants (PEG, phthalates etc.)

I'm running a simple H2O ACN gradient with 0.1% formic acid with positive ESI (Q-TOF).

Any clues?

Thanks.

[agoupax]

From John W. Dolan May article (http://www.chromatographyonline.com/lcg ... ail/773766):

An extra peak, that is not related to the sample itself, in a gradient run typically arises from one of three sources:

late elution from a previous chromatogram
carryover from a previous injection
contamination of the mobile phase (ghost peaks).

I would suggest you to read the rest of his article, I think it woudl help you to fix your problem.

[Vlad Orlovsky]

peak might be related to column bleed