The MS positive charge has a problem

Previously, the results came out like the left side, but now it comes out like the right side. Negative is normal, but there seems to be a problem in positive MS.

Please somebody help me..

  • Looking at the signal axes for the positive signals.  The one where you gave distinct peaks is much smaller than the other.  Seems like a lot more background signal than before?  Has the MS spray chamber been cleaned recently?  That's where I would start.  Maybe the rest of the HPLC could do with a clean/flush, in case the additional background comes from there.

    What do the background mass spectra look like in both sets of data?


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