Chromatography Forum

I use a HP 6890 GC equipped with FID and HP ChemStation Rev A.06.03 software.

If I install two columns in one injector (say, front), and connect each of these two columns with two different detectors (both front and back are used), how can I control the velocities (or flow rates) of these two columns (they have different length, ID, and thickness)?

Any help would be greatly appreciated!

Jimmy

Any adjustment to the head pressure will cause BOTH columns to change in flow. One can place a precolumn restrictor before the wider ID column to change its flow to the desired flow rate once the smaller ID column flow is set correctly.