missing methane peak in rga agilent 6890

[avrc]

Hai everybody,
I am using a Agilent 6890 RGA and I am not getting my methane peak. I am getting 79% N2 and 20% O2 (satisfactory separation) while injecting air and so I think the mol.sieve column is OK. I think there might be some problem in my valve switch-over timings. Can I use FID to detect methane? Since O2, N2 are not going to be detected on FID and I dont have CO in my sample, the peak I get after C5/C6+ peak, I assume, to be methane alone. And I am thinking about calibrating for methane using that peak from FID (and also the next peak in FID I am thinking to use for calibrating C2, since I dont get ethylene in my samples)

Am I right in doing this?

Your comments please.

[Les]

I hear what you say and I do believe you can cal the FID side for methane and ethane. You'll have to be absolutely sure your not going to see any ethylene and you'll never need CO. Many times, I'd like to make those choices, but as time goes by, operations change. Maybe down the road you'll have to include these. For myself, I'd rather work the problem out and get the TCD back to operation. That doesn't mean giving up the FID calibration, just fixing what's broke.

[avrc]

Hi les,

thanks for your reply & I will definitely try to sort out my TCD problem.

[chromatographer1]

I suspect you have a timing issue or a leak in your column valve configuration.

Good luck.

Rod