I suspect you have a leak between BF valve and open split. This way you basically have no He flow into the open split but air diffusing in. Opening the BF does hardly flush the capillary leading to the open split because the leak is too large. Can you put m/z 40 on the first cup to get a readable value and Ar spray the system downstream of the BF?
Von: Stable Isotope Geochemistry [mailto:[log in to unmask]] Im Auftrag von Jeff Salacup
Gesendet: Donnerstag, 20. Oktober 2016 19:31
An: [log in to unmask]
Betreff: [ISOGEOCHEM] GC-TC-irMS leak
Me again. We've got a large leak somewhere. With the GC split in and the backflush closed we get a slowly increasing Ar signal starting around 400 sec and terminating a minute or so later at a full 50 V. Opening the BF and pulling the GC split out results in a slowly decaying Ar signal that can take an hour to really leave the system.
I initially troubleshot it down to the BF. A flow check at the BF vent suggested it wasn't closing and removing it from the flow path got rid of the problem. So I ordered a new one and installed it. It opens and closes but the problem remains.
I've removed the column from the flow path and the problem remains.
The reactor is new... twice now, just to double check.
The inlet liner ferrule is new.
What am I missing?
Two things are infinite: the universe and human stupidity; and I'm not sure about the universe. - Einstein
Jeff Salacup, Ph.D.
Stable Isotope & Biogeochemistry Lab Manager