Shutting down Agilent 597x overnight

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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We had to shut down all of our instruments recently due to a scheduled power outage, so all the GC-MS systems were vented and powered down.

My colleagues and I had a difference of opinion regarding the vent valve. I usually open the vent valve to properly vent the analyser then closing it before leaving the system powered off overnight. Mainly I'm concerned about oil vapour being sucked back into the analyser chamber from the (off) roughing pump and contaminating the thing.

However, they wanted to keep the vent valve closed the whole time to maintain vacuum in the analyser and avoid introducing atmosphere (and thus air/water) into the thing. What would you do in this instance?

Also, I noticed that some of us don't switch off the GC interface/transfer line heater before venting. What are the negative effects if that's not done? It suggests to do it in all the Agilent manuals and also the software.
As long as your rough pump's check valve is working properly there shouldn't be any back flow of oil.
I don't open the vent valves on my 5973,5,7 series for a power shut down. they can hold vacuum for more than a day or two.
Steve Reimer wrote:
As long as your rough pump's check valve is working properly there shouldn't be any back flow of oil.
I don't open the vent valves on my 5973,5,7 series for a power shut down. they can hold vacuum for more than a day or two.


I usually don't worry about it also. If you worry some, then you could increase the carrier flow to 3-4ml/min and it won't take too long to flood the analyzer with Helium (I would not do it if using hydrogen though) which will help reduce the pressure difference at the rough pump valve and still maintain an inert and dry atmosphere inside the analyzer chamber.

Cooling the interface heater is always recommended by Agilent because of burn hazard if you are working inside the analyzer, such at removing the source for cleaning or wiping out the analyzer, ect. I rarely cool it if I am not changing the column.
The past is there to guide us into the future, not to dwell in.
I also think you can leave the vent valve shut. But for a recommendation you could tell us what kind of rough pump you are using: oil or scroll-pump

I guess you have a two stage oil pump and it should be fine with that.

And do you use a turbo or a diffusionpump as a high vac? The diffusions I remember were sometimes more tricky
Applicationspecialist GC, GCMS/(MS) at ThermoFisher
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