AnsweredAssumed Answered

GC/MS leak while inlet pressure and column flow keeps fluctuating

Question asked by lmarsan on Nov 6, 2018
Latest reply on Jun 10, 2019 by m4esti

Hi everyone!

First of all, I would like to thanks in advice any answer to the problem specified below. Also, I'd like to mention that I'm a GC beginner (my Ph.D. started 4 months ago) so I apologize in advance for any so-obvious question.

At our lab, we've been experiencing some problems with what we assumed to be a gas leak. Under normal conditions, a He bottle lasts approx. 6 months; taking into account that during the summer season we didn't run any sample and that the He bottle was replaced in June, this doesn't seem to be a regular thing. Also, it can be observed how the needle of the pressure gauge slightly fluctuates while the device is on. In the end, %N2 reached a higher value than normal (7.5) when autotuning, which led us to an air leak.

Once we started to replace and adjust any consumable that could affect this, we came to a point where inlet pressure and column-1 flow was fluctuating during so long (well, technically it never settled). We checked leaks but we didn't see anything. Anyway and according to what the manual says as well as I could read many threads in this website, I already replaced almost every consumable that could affect to that fluctuation:

  • Gold ring.
  • Liner + o-rings.
  • Septums.
  • Split vent cartridge.

Once we replaced the last one, we finally observed that both pressure and column-1 flow stabilized. BUT, the needle from pressure gauge still fluctuates a bit.

I read in some forums that it could be a welding problem, or even worse: one related to the EPC.

What else I have left to do?


GC Model: Agilent 6890N attached to an MS Agilent 5973.


Thanks again for the help.


Best regards,