Chromatography Forum

We've got a molecular sieve and unibeads dual column setup to test for nitrogen and oxygen in nitrogen tanks. The EP states that column temp is 50C and detector temp can be 50-200C. There's no inlet temp stated. But we have a Gas Valve sampling setup and the inlet is wired to carry He Carrier gas to the valve where sample is then introduced. We have a manually switch to shut off sample gas flow, and push start on the GC simultaneously.

What inlet temp should i set? Currently we have it at 130C the same as the detector. Should the inlet for carrier gas introduction be 50C like the oven? I think the Gas Valve on top of the GC is just ambient temp. Should that have a temperature too? 50C maybe matching the column?

General rule: Tinj>Tcolumn<Tdet. But for N2/O2 it's not important - you can set Tinj from Tambient to 100 C. Tcolumn set 40-50 C, Tdet set 150-200 C. You can have problem with N2/O2 separation, if column is not activated - need to heat column to 300-350 C for about 2 hrs with helium