Unidentified peaks in natural gas

[lotusf33t]

Hi Folks,

I have some small unidentified peaks in a PG&E natural gas sample coming out of a polisher, prior to injection in power generation equipment.

The column is a Poraplot Q and if I have done everything right, here is a picture of the chromatogram detail:


The first comes up between ethane and propane, but not late enough to be propylene by my cals. The second comes up in the rough neighborhood of methanol (though I am not cal'd for methanol) which also does not make much sense. If anyone has ideas what these repeatable small peaks could be, please reply to this thread!

Other details:
Carrier gas - He
Pressure - 20 psig
Temperature - 110°C

Regards,

Jack

[GOM]

Hi Jack

I agree with you that the first unknown between ethane and propane appears to have a relative retention time consistent with H2S on this phase.

Why doesn't it make sense? Is it because it is supposed to have been polished?

Have you tried smelling the sample?

I was also going to suggest sniffing the peak at the detector with the flame off but the level might be too low to detect.

Regards

Ralph

[lotusf33t]

Ralph,

Thanks for your kind reply. My reasoning for thinking the possible H2S peak is not H2S is probably emotionally rooted - i.e. I don't want it to be a large peak of H2S coming out of the polisher, that would mean bad things for the system downstream. Therefore, it is not reasoning at all. I need to take a sample bag from the site and get it out for detailed MS or similar analysis to identify the peaks correctly. My MicroGC is not going to do it in its present state of calibration (no good sulfur data).

Regards,

Jack

[GOM]

Hi Jack

Please let us know how you get on

Regards

Ralph

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth"

"Eliminate all other factors, and the one which remains must be the truth".

Sherlock Holmes