Folw control of each two column contected in one injecror

[jimmyhu]

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

[chromatographer1]

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.