I am a Ph.D. student. I am working with GC-IRMS. We have MAT 253 IRMS along with Ultra trace GC. and GC interfaced with IRMS through GC combustion III.

Recently I had a problem of really high water background after doing maintenance e.g. changing the oxidation catalyst and replacing the septum and liner. However, other backgrounds, e.g., Argon and nitrogen were ok. I tested the instrument for leak check but could not find any leak with Ar gas. After two days, over the weekend, the filament (box and trap values) turned to be zero. I suspected that the filament was broken and we replaced the filament. after replacing the filament, we turned on ion source again after some time, and box ad trap values showed up again. but unfortunately, it went to zero again after 2 minutes. Now this process is continued of showing up of box and trap values and turning off in 2 two minutes.

We changed the nafion membrane two years before.

did someone face the same problem? or can someone suggest any solution regarding this?

I would be very grateful.