Split line testing for Agilent 7890B GC

HI All,

I did a test as specified below to check if there is any issue with the Split Vent. There is a pressure build up when I closed the hole with my finger. Does that indicates the valve is broken and I need to call the Agilent to fix it?

Would this affect the RSD(%) of injections? I am having an issue with my injection repeatability. 

Troubleshooting a Leak in a Split/Splitless Inlet - Articles - GC Portal - Agilent Community

Thank you



  • Please upload the acqmeth.txt file that is underneath the instrument run method subdirectory.  There are many parameters that can affect reproducibility.  What sample type? What solvent? How much are you injecting? What method of injection?  and more....

  • Hi Paulsalverda, thank you for your reply. The issue with high RSD has been resolved with the completion of annual GC maintenance by Agilent. The actual root cause was not identified. 

  • Hello Kris, this valve is normally open and if you put a flowmeter on this vent line you should measure what is shown on the inlet Split Flow setting (in split mode) or Purge Fow (in Splitless mode).  If Gas Saver is enabled and active it should measure what is programmed in the method for Gas Saver Flow.  The only time this vent is fully closed is during Splitless Injections, during the initial portion of the run.  When the Purge Time is reached in Splitless mode this vent will open again at the Purge Flow, and then reduce again to the Gas Saver flow if enabled.  When the valve is open and you block the port, the pressure should rise.  Chances are the issue was caused by liner, septa, and gold seal active sites or slight leakage in the septum if it had many injections.  Split vent trap is also replaced during a PM service.  The trap can also cause some injection variability if contaminated, it can lead to excessive back pressure when injecting in the split mode..  Hope this helps. 

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