5973 MS Leak... (Please help)

Hi there, I have problem with MS unit 5973. main issue is air leak (N2 > 300). ratio N2:O2 is about 3:1.

I Isolated MS from GC. it confirmed leak occured around MS but i have no idea where to begin to  find where the leak..

Im kinda new for this MS.  please help me... share your experience with me .

Thanks with regards.

  • Grab a can of duster and scan for m/z 51 using manual tune. Spray around the mass analyzer door and where the column connects to the MS. Also check around the vent screw as well. A new o-ring or a VERY light coating of high vacuum/stopcock grease should solve your leak. You shouldn't be able to observe any physical amount of grease on the o-ring, holding a gloved finger up to the silicone grease tube opening and giving a slight squeeze will be more than enough for the entire analyzer door.

  • Check the CAS number on the air duster can and then look up an EI spectrum for that compound to make sure you are looking at the right ions. And make sure the air duster DOES NOT contain a bittering agent. It may be necessary to purchase it from a scientific supply company to get some without bittering agent. But 70 eV is corrrect: open manual tune, set it to either scan from 40-100 or profile on the masses you expect from the air duster. Spray the common leak sites (analyzer door, transfer line, vent valve) and look for response. If you need to spray the inlet keep in mind the leak test gas would need to travel through the column and it may take ~1 minute or so until you see any response. If you are spraying up-stream of the column I recommend doing 3 short pulses of spray with 1-2 seconds in between each pulse as it is easier to see the pulses and confirm that yes this is the leak testing gas after it traveled through the column.

Was this helpful?