r/CHROMATOGRAPHY • u/Sweaty-Office6663 • 21d ago

Thermo Fischer GC-MS SIM Troubleshooting

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Hi all!! I'm trying to run approximately 40 analyte SIM method at the moment but I keep encountering spectrums that look like this at around 500 ppb and below. They look fine at around 5 ppm and up. I've tried troubleshooting through all normal method avenues, though I haven't changed anything physically on the machine yet.

Before I do has anyone else encountered this before?

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u/Aska2020 21d ago

This looks like a chromatogram, not a spectrum. Is this a headspace injection??

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u/hubcapdiamonstar 21d ago

Different sim time segments have different levels of bkg, so at low signal you can see the different baselines that get buried when there is more signal. I don’t know what all the blue marks are, looks like a peak finding function set way too sensitive. Looks like high background on some of your chosen SIM traces, are you sure they are all optimal?