PCI tune "Improper masses for mass axis calibration" error code on 5977c

PCI Methane tune "Improper masses for mass axis calibration" error code on 5977c. Seems methane not being detected. Not sure where to go from here after testing out issues below. 

Have tried the following troubleshooting: 

  • Confirmed ms function with EI source.
  • Checked that the masses are correct 17, 29, 41 for methane tune.  
  • No air or water peak
  • Tightened connections
  • checked the lines for leaks. 
  • Used different tune files to see if bad tune file. 
  • Interface tip seal examined and reinstalled.  


-Instrument installed back on 1/10 and tuned

- CI source not used during this time 1/10-3/13

- CI tune on 3/13 and noticed 29 abundance significantly decreased 

- No peaks detected in sample run 3/13

-4/11  methane tune:

  • The methane pressure is 10 to 25 psi?  It must never be higher than 50 psi or will permanently damage the CI reagent gas flow controller.

    The biggest cause of CI tune failures are filament alignment, filament degradation, and normal dirty ion source.  The CI filament is one straight Rhenium wire that must be exactly aligned with the 0.5 mm id hole in the ion source body. If it is even very slightly misaligned the tune may have troubles.  The easiest and fastest thing for you to try is to vent it and replace the CI filament with an EI filament, pump it down, let it thermally equilibrate, and test it again.  The four turn EI filament will have some portion aligned and so that will tell you relatively quickly if that is the issue.

  • Methane at 25 psi. Thanks for suggestion! Will test this out next. 

  • Update: I checked filament and looks fine. Weird when switching from EI to CI source the tune fails 3x in a row and then passes every time after that. This happened twice after switching source. The tunes that pass though do not seem like everything is fine though and again seems like a methane flow issue. Methane is at 2x (~40%) what recommended value is (20%) and show max emission & electron energy values. Purged lines for a longer time per another suggestion but still did not change. Samples run though seem to be working okay though. Any further suggestions would be helpful out side of it being a reagent flow controller issue

  • Try an EI filament, even if you think the CI filament installed "looks" good.   

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