-
- Posts: 35
- Joined: Wed Dec 21, 2016 12:38 am
we have been running PAH on our 7820/5977 system for a few years with pretty reliable sensitivity (2-250 ppb).
The past few months have been another story, with lower area counts, some PAH standards dropping out entirely at the lower concentration.
The mass spec side seems ok after cleaning the source, replacing the EM, and now getting good tune reports.
Still no joy.
So the GC has undergone many maintenance procedures - new column, liner, ferrule, septa clean the inlet body with solvent, replace split vent cartridge. No improvement.
About all I can think of to try on the GC is replace the inlet G1544-80570, in case ours is too far gone with active sites.
While waiting for that part I started leak checking again, and saw that the service mode Inlet Leak Check showed a small leak.
At 15 psi, the total flow is 3.7 and the column flow is 1.5. An Agilent engineer I spoke to said this is close to spec and would not cause a loss of area counts in some PAH, rather it would affect all of them if there were a large leak.
Is this right? I can't find the allowable limits for this test anywhere and without a leak tester it is hard to find small leaks.
If there's any thoughts on what direction to go here, I would greatly appreciate it.
thanks!