Chromatography Forum

I would like to explore using hydrogen as a carrier on our fid instruments currently using helium. is it possible to plumb the front fid detector with hydrogen and leave the rear detector with helium on a old 5890? this way i can still run the rear detector while doing method development on the front.

I'm confused: for your future changeover to hydrogen carrier, you still have hydrogen going to the detector. If you use any helium in the detector then, that would be as make-up gas, or you could use nitrogen for that.

So I think you want the carrier to be hydrogen for one inlet and to be helium for the other inlet. If so, inide the panel on the left side of the 5890, just run separate helium and hydrogen tubing to the appropriate inlet controls.

We run helium as carrier, and our 5890 units have a "tee" fitting inside that panel so one line feeds both inlets.

Unless you want to have method development and routine running simultaneously (which might be tricky !) the the easiest is to use a 3-way valve upstream of the GC to select either hydrogen or helium to go to the carrier gas input connector. You will have the same gas in both columns at any given time, but you will only be using one of them at a time so this will not matter.

Peter

I agree with the consumer products guy. We use hydrogen carrier, nitrogen make-up and reduce the fid hydrogen by the amount supplied from the column flow. It is all a matter of plumbing to maintain helium carrier to the other column and detector.