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- Posts: 8
- Joined: Tue Jul 11, 2017 9:37 am
I am working with a GC FID 6890 Agilent. The column installed is a 530 um column (BP21 SGE). Our method works with nitrogen as a carrier gas, at a column flow of 1.6 (16 cm/sec), and a split ratio of 1:15. All giving a pressure in the inlet of 1.4 psi and a total flow of aprox 27mL/min.
We have been working with this method for about 3 years.
Slowly, we started noticing problems to keep the pressure at 1.4 in the inlet, until the GC actually gave up. We can not keep a pressure lower than 2psi. This led as well into problems keeping the flame on in the detector. The flows of H2, air and make up N2 are well mantained, but it can not keep the flame on.
This is the isolation of the problem that I have been doing:
- Starting from the detector. The JEt and the FID have been cleaned (by a technitian), and we see that flame can be mantained when instead of the column there is an stopper nut attached to the FID. So we do not think it is the FID itself, but rather leaks upstream from the detector.
- We have also seen that the FID can keep the flame on when the column is installed in the FID, but not connected to the inlet. Instead, we cap the column with a septum in the inlet side. This tells me that the column itself is not damaged.
- When I install the column in the inlet, the detector fails to ingite. I have tried with several pressures in the inlet (2-8-10-25 psi), and the same thing happens. (I can not keep any lower than 2 psi)
This would tell me that the issue might be related to the connection between the column and the inlet, and might be the same reason why we can not keep pressures lower than 2 in the inlet.
- To see if we had porblems in the connection between the inlet and the column I left only a few cm of column in the inlet and capped it with a septum. The inlet could mantain without problems the pressure at 1.4psi. So this tells me that the issue is actually not in the connection between the inlet and the column. So now I do not know anymore.....
Any ideas??
Thanks in advance
Anna