Chromatography Forum

Hello,

im trying to prep a GC-MS for a upcoming installation of a pyrolyzer. However I cannot get the leak under control. The leak check of the system shows me a persistent 7-9 % leak on the system. The step I have taken so far:

- Check pressure of vacuum: Amazing, 37 mTorr foreline pressure and 5E-8 Torr high vac
- Check system with Restek leak detector: nothing
- Check gas lines with detector: nothing
- shut down MS, remove column, do bubble test: He is flowing
- plug up column end with septum, do leak test of GC: system is tight.
- Replace MS side ferrule: no improvement
- Check system with leak detector again: nothing
- refill cal standard: no improvement
- put system into manual tune, spray with "freeze 75" compartment by compartment, no correponding peak shows up

I am at the end of my wisdom here. I'm supposed to hand in my dissertation in spring and still have measurments to do. Someone please save me!

Found the problem finally. I was very close to opening the MS. Tried to increase split flow to see what happens with the leak. Turns out someone set the gas saver flow to 0 mL/min. So the system was pulling air through the split assembly. After I shut it on again the leak reduced to 0.3%.