Flow In saver gas


Which is the correct flow in saver gas for GC/MS? I have it at 20ml/min. 

  • It's not safe for your columns to set the gas saver less than 20 ml/min.   There can be back diffusion of air into the inlet and so into the liner and the column. If the inlet is hot, that oxygen can cause issues with the inertness of the liner. Columns can be damaged by as little as 50ppm oxygen.  The low inlet pressure because the column outlet is at vacuum in a mass spectrometer allow this to happen even easier. The oxygen in the column goes into the source and causes issues inside the hot MS.  20 ml/min is the safest absolute minimum and a bit higher may be a bit safer depending on other settings.   If you want to save helium there are other ways that are better than just trying to turn the flows down.

  • Is this necessary on a GC when it is sitting idle for long periods of time or can I turn off the gas saver and just run a 1.5 ml\min flow to the column?  Currently,  I have a split inlet with a flow of 1.5ml\min, septum purge of 1 ml\min and column flow of 1.5ml\min with a helium carrier gas.  This is strictly when the unit is in standby.  Sometimes we don't run samples for weeks, so want to conserve helium.  Also wondering if it is a straight forward scenario to even convert to high purity nitrogen when in standby mode?  Thx

  • I'd refer to Paul's comments above regarding diffusion of air into the inlet when the inlet total flow gets too low.  Switching to an alternate such as N2 is pretty straightforward.  Agilent even has a helium conservation module for 7890 and 8890 GCs to simplify and automate the process: https://www.agilent.com/en/product/gas-chromatography/gc-systems/helium-conservation-module-for-gc 

Reply Children
Was this helpful?