Ion 44 baseline

Hi! We are actually having some issues with my GC-MS. Some months ago started appearing an annoying ion during all the TIC, the m/z = 44. Some threads comment that could be some air leak. we have checked all the possible parts of the chromatograph and seems not to be that. Also, the autotunes are apparently correct and they do not show me any leak. 

On the other hand, ions 18 (water), 28 (nitrogen) and 32 (oxigen) are very high. I'll attach to this post some screenshots with a blank TIC. The peaks of the blank TIC are due to the m/z = 28 (nitrogen). We want to solve this problem because some peaks appear under the baseline and it is quite annoying.

 

Thank you for your attention!

attachments.zip

Top Replies

  • hello ,

     

    1) to see when/how the unwanted peaks come:

                   please create an extracted TIC once: Chromatogram > Extract ion chromatogram > type in all masses (18, 28...)

    EXAMPLE:

      

    now we can see if…

Parents
  • hello ,

     

    1) to see when/how the unwanted peaks come:

                   please create an extracted TIC once: Chromatogram > Extract ion chromatogram > type in all masses (18, 28...)

    EXAMPLE:

      

    now we can see if it is a unique entry or if it changes during the run.

     

    2) how is the inlet EPC set:

          ~ which inlet? (S/SL, MMi...)

          ~ which mode? (S, splitless...)

          ~ which total flow? or is GasSaver on?

                  

          ~Background:

            Some inlets, although leak free, tend to increase N2 values if the total flow during the run is very low.

               Simulation: manual tune > SCAN.

                 Now set the total as it is in run mode,

                   if nothing is found: increase the temperature of the GC

           

    3) For leak search @MSD a spray is mandatory:

          (aero duster spray or) electronic freeze spray down to -45°C (inside ACQ: manual scan: profile on mass 83)

          Then ferrules are not stressed too much, because many users have already destroyed the MS transferline by preventive "over" tightening.

     

             typical spray (hopefully this will not be seen as advertising here ;-) ) 

       

    regards, M

Reply
  • hello ,

     

    1) to see when/how the unwanted peaks come:

                   please create an extracted TIC once: Chromatogram > Extract ion chromatogram > type in all masses (18, 28...)

    EXAMPLE:

      

    now we can see if it is a unique entry or if it changes during the run.

     

    2) how is the inlet EPC set:

          ~ which inlet? (S/SL, MMi...)

          ~ which mode? (S, splitless...)

          ~ which total flow? or is GasSaver on?

                  

          ~Background:

            Some inlets, although leak free, tend to increase N2 values if the total flow during the run is very low.

               Simulation: manual tune > SCAN.

                 Now set the total as it is in run mode,

                   if nothing is found: increase the temperature of the GC

           

    3) For leak search @MSD a spray is mandatory:

          (aero duster spray or) electronic freeze spray down to -45°C (inside ACQ: manual scan: profile on mass 83)

          Then ferrules are not stressed too much, because many users have already destroyed the MS transferline by preventive "over" tightening.

     

             typical spray (hopefully this will not be seen as advertising here ;-) ) 

       

    regards, M

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