Ion at every mass

Hi 

I have a 7890/5975C that has scans that come out like this. This started months ago. I have cleaned the source, inlet, replaced the copper tubing for my carrier gas and checked the manifold many times. My tune report looks normal aside from a bit of moisture. I haven't been able to find any leaks. Multiplier gain is low. Filaments are new. Ions also appear in the TIC as well. Where could this be coming from? I've capped the detector and it appears to go away. Could this be an issue with the electron multiplier? Am I missing something? This is a relatively new instrument to me. 

 

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  • What is the complaint?  The tune shows 166 peaks - a typical number. Air and water are less than 5% of 69 - decent but not perfect. The tune numbers look pretty good. My only worry would be the precursor on 69. I would change the quad polarity to NEG, save the tune file, then tune again and see if the tune ion peak shapes are more symmetrical.

    If you scan lower than 45 you will always see a bit of air/water. Maybe not much, but always some.  The 44 is pretty high, too. 44 is CO2 and is typically a very small percentage, 0.03%.  It is also seen coming from the graphite/vespel ferrule on the transferline.  

    What is your acquisition threshold?   With your current electron multiplier setting and tune parameters it should be maybe 1000.... so that any peaks lower than 1000 are discarded.  That's sort of a typical number/range, too.  

    Do you need to scan lower than 45? Most applications do not need to see peaks of interest with ions lower than that.

    And let us know!

  • My concern is that it also shows up in the TIC. There is quite a bit of noise in the chromatography.

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