7890A/5975C GCMS Pressure Issues

Hi everyone,

In running FAME samples on a DB23 column, I keep getting an error message of "Neither GC nor MS collected, consult logbook". This started with a one time error message of "Front Septum Purge Shutdown", but  it has not popped up since I was first having issues. The logbook gives the error message "Front inlet pressure not ready Run Time 0.20" with every current test run that I do. My injections seem to go fine and my system eventually reaches the correct pressures, but in monitoring the actual vs. setpoint log, I can see that my instrumental pressure is lagging behind the setpoint by about 0.015psi as it climbs in my method. I am running in splitless mode with a full gas tank and max pressure of ~20psi so I am unclear where my issues are coming from and why the pressure incline is so slow. In terms of troubleshooting, here is what I have done so far:

1) Leak tests for inlet/tank/added PTFE tape around joints that may be leaking

2) replaced the front inlet septum, gold/washer, checked the liner (old but barely gets used, <10 samples per month), trimmed the column for clogs 

3) Tuned the MS, run basically every diagnostic test in the service mode and they all came back fine

4) Tried running with and without gas saver on, both had the same issue

Any ideas on what could be an issue/what my next step should be? Thank you!!

  • PTFE is to be used ONLY on pipe thread fittings. It is NEVER to be used on the tank to regulator connection or any Swagelok fittings as it gets in the way of the sealing surfaces. Most people dramatically overtighten Swagelok fittings and cause leaks.  If there is a leak at a Swagelok fitting the best thing to do is to cut it off and remake it with new ferrules.  Do not overtighten it!  1/8" Swagelok only needs to be tightened 3/4 of a turn past hard finger tight to seal properly.

    The electronic pressure control modules need 20 psi or greater supply pressure than the maximum pressure they are required to supply.  So if the inlet goes to, say, 30 psi during the run or during a pulsed splitless method, then the supply must be at least 50 psi or greater.   I set tanks to 80 psi since there is usually a line on the regulator at that pressure. I even use a sharpie and draw a mark over the gauge needle at 80 so that it's easy to see if the needle has dropped.

    0.015 psi lag is pretty normal during programmed runs.  That is a tiny amount of pressure.

    The Split/Splitless inlet needs 20 ml/min or more of total flow to function properly. For a GCMS, the column flow is usually 1.2 ml/min, septum purge at 3.0 ml/min, and split vent at 15.8 ml/min....or higher.  If you are trying to run a split ratio of less than about 13.2:1, flows don't necessarily function properly.  If you are running splitless, the system takes care of the inlet flows for you, but you still need to sweep the inlet quickly at the end of the splitless time, so purge flow at 60 ml/min and then gas saver at 20 ml/min at 2.00 minutes, the default.

    "Neither GC nor MS data collected, consult logbook" means either the system stopped before the solvent delay was over, the filament didn't turn on, the remote start cable got disconnected from the MS, or a number of other possibilities.   If the MS is tuning and the GC is not beeping and shutting down - edit your method to change it to Split, 100:1, save it with a new name, and see if it works then.  Let us know what happens.

  • Thank you so much for your detailed helpful message! I have removed any PTFE not on the pipe thread fittings and made sure nothing is too tight, I keep our helium tank at 80psi (and use the sharpie trick too!).

    My methods are all splitless so the parameters set by the system are: Total flow 18.5mL/min (11.089psi), column flow 0.5mL/min on a DB23 column, septum purge flow 3mL/min, split vent 15mL/min for 0.75 min, and gas saver 20mL/min for 2 min.

    I put in a split inlet liner and tried to run with the 100:1 Split parameters you suggested, but neither the GC nor MS collected again and I had an error message on the GC about "Septum Purge Flow Shutdown". I'm going to edit my method to increase the purge flow and see if that helps, otherwise I am worried that I might have an issue with my EPC.

    Based on my description, does an EPC issue seem like a possibility? I appreciate the help!

  • DB23 column - what dimensions?  Typical Splitless parameters would be - Split vent 60 ml/min at 0.75 and then gas saver 20ml/min after 2 minutes.

    and yes, it sounds like an EPC module issue could be a possibility.  Please call your local Agilent service number and set up a repair visit.

  • Hello, I wanted to update if anybody is following along that the issue is resolved! Those are the splitless parameters I swapped to which helped, but I had someone look at the instrument and it turned out to be an issue with the mass spec, not the GC. The filament on the MS was not working properly which was preventing data from being collected, but after fixing that issue the instrument works well now. Thank you for the help!

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