m/z shift in quadrupoles
Posted: Mon Sep 16, 2024 4:50 pm
I have the results of a Mass Spec run: MassLynx, SQD, Electrospray (both positive and negative).
Across some peaks, when looking at individual spectra, I see that the m/z of the compound slightly shifts left-right. So when summing the spectra across the whole peak, the resulting isotopic pattern doesn't match the expected one:
And I'm quite sure it's the right compound because it's the right compound. If this happens in the positive mode, there's still negative mode where we can double-check - and oftentimes the pattern there is within the expected boundaries:
My assumption is that the data was noisy, and so these shifts are due to the centroiding. We'll try go get a continuum next time. How common is this? Could there be some configuration on the instrument side that can help remedy this?
Across some peaks, when looking at individual spectra, I see that the m/z of the compound slightly shifts left-right. So when summing the spectra across the whole peak, the resulting isotopic pattern doesn't match the expected one:
And I'm quite sure it's the right compound because it's the right compound. If this happens in the positive mode, there's still negative mode where we can double-check - and oftentimes the pattern there is within the expected boundaries:
My assumption is that the data was noisy, and so these shifts are due to the centroiding. We'll try go get a continuum next time. How common is this? Could there be some configuration on the instrument side that can help remedy this?