high nitrogen and oxygen value on tune

[erasmus1967]

Good morning. Today I changed the big trap helium in the Agilent GC(7890A)/MS(5975C), but as before, I continue to have a high nitrogen (47.8%) and oxygen (12.7%) value on tune. I tried change the helium tank, the septum and the liner but nothing. I think it's an air leak, What can I do?

[Consumer Products Guy]

I think it's an air leak

I think so too.

I'd block off the MSD at its inlet in the GC oven, and see what that shows. That should isolate whether such leak is in the MSD or the GC.

[AICMM]

Same idea, slightly different. Disconnect the column at the inlet (cold) and plug it with a septa. Means you don't have to vent the MS. Then spray with dust off or dry ice or isopropanol and look for appropriate ions.

Best regards,

AICMM

[Consumer Products Guy]

Same idea, slightly different. Disconnect the column at the inlet (cold) and plug it with a septa. Means you don't have to vent the MS. Then spray with dust off or dry ice or isopropanol and look for appropriate ions.

Best regards,

AICMM

Good idea.