GCMS 7000D peak Broadening


My colleague is working on the GCMS to extract an analyte and its metabolite (she is derivatising in her method). The method has been working until a few weeks ago when just her peak metabolite started to look quite small and broad. She has trimmed the column, she baked it and then changed it, changed the liner, she checked the vials and changed it (just in case was related to the septa). The solution is regularly changed as well. However, the peak still looks the same. Is there something else she can try? 


  • What analyte, metabolite, and derivatization method?  Do you have other analytes that look normal?  A standard to inject to make sure that the system is functioning properly? Have you tried running in MS1 Scan mode instead of MRM?  -- scan 45 to 450, scan time 250 ms, threshold zero.  That test can tell you if there is other stuff coming out at the same time as your peak(s) of interest that might be interfering. MRM only looks at a very few ions but if there is other stuff in there while your peak(s) of interest are eluting it can cause suppression.  If it passes the tune, then the MS is probably not the problem. Chromatographic peak shape issues are sample preparation, sampling, injection port, or column related. 

    Also, please upload the acqmeth.txt file that is in Windows underneath the xxxx.M method subdirectory. That file includes the GC parameters and maybe some recommendations can be made to improve those.

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