Contamination m/z 118.1230 on a LC-QTOF


Is anyone had struggle with the m/z 118.1230 as a contaminant, in positive ionisation mode on a LC-QTOF?

We do lipidomic and it create a lot of problems on lipids which ionise as an [M+NH4]+ as phosphatidylinositols, cholesteryl esters and triglycerids.

Do you have any idea where it could come from? How we can reduce or eliminate the signal?

Thank you in advance!

Parents Reply
  • Our mobile phase is a mix of MTBE, methanol and acetonitrile. I tested all solvant plus water separately by direct infusion via bottle B in tune mode. The 118.1230 is always present. I tested different batch of ammonium formate and old vs new bottle of solvent. I washed capillary and all part of the source that I have access. I changed column.

    The contaminant is there since 2019 and present in our two LC-QTOF but the problem of adduct begin to be a struggle in the last month. We think that the problem came maybe from the nitrogen.

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