FID parameters

[Krismo]

Hi!
We have GC/FID with 2 injectors and 2 detectors, which we will use one at a time, and my question is, what parameters should have detector that is not in use? Should flame be on as well or is it enough to raise temperature in detector and establish column flow?

Best regards,
Krismo

[Peter Apps]

If the detector has nothing to detect you do not need to have the flame on. iow, keep the detector temperature at its working value, with carrier flow through the column.

Peter

[larkl]

I'll second Peter's recommendation. Keep it hot, leave the flame off, and keep flow through the column.

[Krismo]

Thank you for your answer. After second detecor was installed a problem occured. Althogh i have only minimum column flow in unused column, i cannot use make-up gas 45 ml/min in detector that is in use, flame will not go on. If i change make-up gas flow to 10 ml/min it will lit. This is much lower than recommended, can i work like that?
Regards,
Krismo

[Peter Apps]

Hi Krismo

Unless there is something seriously wrong with the installation of the gas lines, the carrier flow in the second (unused) column has nothing at all to do with the gas flows to the first (used) detector.

45 ml/min is higher than I would expect for make-up and will give you problems in igniting the flame, but you should not need to go as low as 10 ml/min. Check that the flow of hydrogen and air are correct, both as set on the GC and as actually delivered to the detector, and measured with a flow meter.

You can run with the makeup at 10 ml.min, but the problems that you describe are symptoms of other things being wrong, and you need to troubleshoot fully.

Peter