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GC/MS Leak (Intuvo 9000+5977B SQMSD)

lewastro

Hello,

I am having a problem with GC/MS system leaking (Intuvo 9000 with 5977B SQMSD).

Pretty much out of nowhere, a leak in GC side appeared. MS rules out, as it was enclosed - and leak is non appearing, both in AWL check and simply while profiling air masses. Most usually, with AWL check, there used to be about ~2-3% N2+O2 in system. Now the N2 is jumping ~15-25% and O2 to about 5-7% - nothing was changed prior to it. Leak can't be detected inside GC using air canister, neither with hexane - while profiling appropriate masses for both.

Using the GC "Leak and Restriction" test, system shows unstable (jumping), about 0.1ml flow rate towards restriction.

What has been changed so far:

  • Gas Filter (Big Universal Trap);
  • Septum;
  • Liner and its O-ring;
  • Guard Chip (split/splitless);
  • All compression bolts (except for guard chip);
  • Column and MS Line gaskets (polyimide, 350°C).

Appreciate all the suggestions and ideas, thank you!

  • 0 in reply to paulsalverda

    Thank you for the suggestion regarding the GasSaver flow. Are there any recommended intervals for that function - or that depends solely on total flow of the inlet? It seemed a bit for a smaller side (as in 15ml/min) but didn't know if that would be enough or not.

    About the column. Are there any other points why you would you recommend using narrower column instead of 0.32mm one? Or is it solely because of higher sensitivity for MS using lower column flow rate?

    Thanks!

  • 0 in reply to lewastro

    There are a few ways to use GasSaver. If you're using the inlet in Split mode, the GasSaver should be turned on as soon as you know for sure that all of the sample has exited the inlet and is on the column. Two minutes is typical, but it could be shorter, especially if running very high split flows.  If using the inlet in Splitless or Pulsed Splitless mode or ramping the temperature of an MMI inlet, the GasSaver time must be longer. Too low a GasSaver flow fakes operators into thinking there is an air leak. 

    Or, set the Gas Saver time to after the run is already complete.  Then Gas Saver will be ON when the GC is not running but OFF during the run, ensuring that the flows are sufficient.    If you need to save even more helium, consider purchasing a Helium Gas Saver module for your GC so that nitrogen is used all of the time that the instrument is not running samples.

    The smallest volume injected of the lowest concentration of the cleanest sample possible results in the least amount of inlet, column, and MS maintenance.  A narrower bore column has lower loading capacity and makes sharper peaks. The smallest peak of interest only needs to be 3x to 5x taller than the average background baseline.  Too many have huge peaks and then wonder at the associated maintenance.

  • 0 in reply to paulsalverda

    Very informative insights about the GasSaver! Concerning my peaks of interest - they are highly symmetrical and not overloaded, but I guess I could push it into the lower side, so the sensitivity would be higher.

    If I would have any technical questions in the future, could I contact you? Thank you very much!

  • 0 in reply to lewastro

    Post questions on the community. I'm one of the folks answering. You can also call the toll-free number in your country and talk to someone on the phone.

    and you are welcome!

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