Leak in GC/MS

[MrGC]

To be on the safe side vent MS prior to removing the nut.

Vent.

If you had a capillary column attached - which would restrict any air flow in - then I'd say different.

Thank you! So switching from column to the nut I'm using to isolate the MS would be okay...
Is it really primarily due to the turbo pump or is there any other reasoning?

[Peter Apps]

VENT for sure.

If you just remove the nut and ferrule you will get a huge inrush of lab air which is bad for the turbo, might carry ferrule fragments to places you don't want them, and will have to be pumped out anyway.

If you vent the chamber will fill with helium (assuming yours is plumbed like mine) and so the only air that gets in is the bit that diffuses down the transfer line while you get the column threaded and sealed.

Peter

[MrGC]

A big thank you to everyone who replied to this thread. The leak is finally gone. It's really a great and interesting forum

Does anyone, by the way, have experience with the use of high vacuum grease on the o-ring of the analyzer chamber? I heard some people complain about contaminants occurring in the measurements. (Probably because of too much applied grease I'd assume)

[Consumer Products Guy]

I'd stay away from grease.

[Bigbear]

If you have an Agilent system, we have had leaks where the transfer line attaches to the vacuum box. The leak would "decrease" with a cool transfer line. The fix is replacing the O-ring that seals the transfer line.