Chromatography Forum

I just acquired a new Agilent 7890A GC equipped with a TCD, FID, and microECD. We currently have two PLOT columns installed - 30 m x 0.32 mm, 3.0 um and 30 m x 0.32, 1.5 um - with a Dean's Switch between them (i.e., essentially, the columns are sequential) and run nitrogen as our carrier and makeup gas.

Now that our GC system is fully installed, I'd like to start developing our methods for analysis, but I would like to avoid turning the GC off as much as possible. Can anyone recommend flows/temperatures for the inlet, columns, detectors for a standby method (overnight, over weekends)? Should the detectors be turned off while not in use? The air/hydrogen for the FID is only for the flame, so I can turn those gases off completely when the FID is not in use, correct?

Thanks for your help,
GHGirl

When not in use you can reduce the temperatures of everything, I like to keep things above the boiling point of water so no moisture builds up in the system.

You can turn off the air and hydrogen, and reduce the make up flow to maybe 5-10 mL/min for the FID.

I would keep some make up flowing through the other detectors as well, cap them when no column is installed to avoid dust or other contaminants getting inside.

For the inlet you can set it to a split of like 5:1 and a column flow of 0.5 mL/min and that should be sufficient.

Thanks for the helpful response, Aldehyde!

Sure. If you can spare it all of those flows were lowballed, if you can afford it bump them up a bit.

And if helium cost is an issue depending on your assay moving to hydrogen carrier can be helpful (at least keep it in mind for the future, helium prices aren't going down.)

Yes turn the air and hydrogen off when on standby. You can leave the other zones hot if you want, to reduce equlibration when starting up, but for longer-term standby then turn off temps for inlet, detector etc. they will heat up quickly enough anyway.