Hydrocarbon analysis on FID with in-line methanizer

[dr_methane]

Hi All,
I am trying to quantify some tracer gasses (camping gas, mostly propane, butane, and isobutane) I added to streams. I bubbled the gasses in, and then collected bubble-free water and equilibrated it with ambient air before storing the gas-only sample.

Our GC has an FID with a methanizer and I have been able to get reliable peak times and sizes from my dry standards, but when I try running samples I get an exponential loss of signal regardless of run order or sample contents. I tried ramping up the oven temp to 110 and having a dessicant in my injection, but it does not help. Is my methanizer (turned "off") causing this problem? Could it be other gunk in the tracer gas I used? My baselines are stable and I am not getting any mystery peaks.

Thanks

[AICMM]

dr_methane,

Are you keeping your methanizer warm? That is to say, over something like 200C? Might be acting like a trap. (A long shot but something to think about.)

Second, have you looked at by-passing the methanizer? Should be as simple as a union from column to methanizer transfer line leading to the detector.

Best regards,

AICMM

[dr_methane]

Thanks for the suggestion! I ended up removing the catalyst all together and having an empty methanizer tube. I am still waiting for everything to warm back up and stabilize, so hopefully this will do it!