We have a new contaminant in our LC-MS analysis of peptides eluted using 2D LC (high/lowPH RPLC) with an m/z value of 449.1, associated with a peak at 109.1, probably an in-source fragment. Anyone seen this before ?
I considered that, but I would expect to see a ladder of peaks differing by 44 ? It is positive ion mode indeed.
Bart,
can you say whether the signal is singly or doubly charged? What would be interesting as well is how exact is the mass determination (which instrument type did you use)? Triton based contaminants would appear at at 449.287, another option would be Dicyclohexylurea at 449.385. If it is a doubly charged signal, a sodiated Tween based compound would potentially fit. However, as you already mentioned, for Triton as well as for Tween based contaminants you should see more signals with 44 (or 22 m/z for doubly charged signal). The urea might originate from DCC used in peptides synthesis or organic synthesis. Could this be possible based on the samples you ran on the system? The urea signal at 449 originates from a dimer, thus you should also be able to observe the monomer at 225.196 Da, is this the case?
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