Chromatography Forum

Hi Everyone,

I have an issue with a loss of sensitivity with a Agilent 7890 that's equipped with a OI PID/FID tandem detector that we test gas samples on.

I recently installed the detector after it came back from repair. I have lost 50% sensitivity on all my compounds when testing with the detector compared to my loaner detector and before it was sent back for repair.

I checked my trap system and sampling system, everything is leak tight. My baseline is clean and isn't noise. The peaks come out great just not at the height I used to seem them at. I even recleaned and reinstalled the detector.

I did install a new column along with the detector however, I would imagine that if it were leaking or installed incorrectly that I would have baseline issues.

Any advice anyone could provide would be a big help.

I have not worked with this setup for years, but I would check the seal between the PID and the FID and ensure no ferrule pieces are clogging the interface. The o-ring that seals against the lamp can be a trouble area as well. I think there may be a 'correct' insertion lenghth of the column into the detector; it is possible to insert that too far. Make up and detector gas flows are worth a look.

Thanks for your advice. I checked my flows and they look good; It's probably the o-ring I'm assuming. When I have some down time on the instrument. I will take a look at it.

I had a similar issue with my FID a few months back. After some frustration while trouble shooting I replaced my syringe and the sensitivity returned.