Chromatography Forum

Hi all,
please excuse me if this seems like a dumb question:

Im currently using a Agilent GC 6890. I have a front inlet CoC that is using a MS detector and a back inlet with a split/splitless using a PFPD.

Im currently only using the front inlet and detector, so whats going on at the back? what conditions should this be set to in order minimize He use? I realize that some gas flow must be going to the column in the back to keep it safe from getting ruined (I have it set at .5 ml/min), but not sure about the flows at the inlet? The back detector and inlet are used very sparingly! Maybe once a month.

Here are the current conditions I have set for my idle split/splitless inlet (I've included the back column conditions as well), while I run samples on my front inlet+detector:

Mode:Splitless (should this be set to split?)
Temp: 55 (is this too low?)
Pressure: .4
Purge time: 0
Purge flow: 3
Total flow: 23.5
Gas Saver (on)
Column flow: .5
Column pressure: .4
Velocity: 4
Constant velocity
*The back detector is not lit and its corresponding gasses are shut off.

Thanks for any advice/suggestions

Hello

If you use back channel once a month I'd recommend to remove column and cap inlet/detector with blank nut. (pressure and temp for inlet can be off, you can leave low flow for makeup gas in detector)
For S/Sl inlet and FPD you don't need a lot of time to set up/stabilize column so it is better to remove column and install it when you need it.

Regards

Tomasz Kubowicz