My GCMSMS sensitivity has decreased dramatically, there are no leaks, the source was cleaned, and the column is relatively new. The auto tune report compared with the instrument was working at optimal condition is the abundance has decreased from 18,947,928 to 7,532,691 for m/z 69, and the Max gain factor has decreased gradually from 3000 to 268 despite source cleaning. Does this have anything to do with the Electron Multiplier?
I agree with Poojary and Bhattacharyya....but i would like to ask how long you have your system and is it on a 24 hours working? thirdly what do you analyze most?
But generally when the sensitivity decreases you can increase detector voltage and tune to see if there is any improvement...i use a Shimadzu GCMS QP-2010 Ultra.
In my case last time, the problem was caused by filaments. Try to install two new filaments. Somewhy, 1 new and 1 old filament did not work properly on my 5973N MS. Another reason may be poor contact between filament and wires. When I had this problem on a newer 5975C with a transparent window, I could see the very poor light from the working filament. Another problem may be caused by a very dirty repeller. Problem with electron multiplier typically cause extra noise, total signal does not drop.
Did you check the vacuum? small leakage can also decrease sensitivity.
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