Chromatography Forum

Hi all
I am looking to purchase a refurbished GC to measure CO2, CH4 and N2O. In the past I have used a Perkin Elmer 500 with FID (methanizer) and ECD. We used acetylene incubations of soil to measure denitrification so we had a PreVent and a Backflush to prevent O2 and acetylene going to the ECD (though Im not sure which was for which?). I am also not sure how the valves were setup for this application and whether there is a switch to prevent CO2 going to the ECD too (Deans switch??). There are lots of possible configurations

http://www.vici.com/support/app/2p_japp.php

and I wondered if anyone new the best setup? Also, I think we had split/splitless and used nitrogen as a carrier though helium may be preferable or argon/methane.

Cheers

Hi! I work as an engineer at Shimadzu Scientific Instruments...
I think something like our Greenhouse Gas analyzer would be what you need. I think you are probably going to want to stick with the Methanizer-FID combo and an ECD. Are you doing headspace from any sort of container?
Typically you would want some sort of valve to back flush (anything you aren't interested in) and another valve to switch between the detectors. I also typically see helium as a carrier with an Argon Methane ECD reaction gas.

Other than the three compounds you mentioned was there anything else you were looking for?

sbonnett,

Your gases are light. Therefore, I would suggest a regular switching valve rather than a Deans switch. The Deans switch takes more time setting up and you will not take advantage of the main advantage of the Deans, namely the ability to take it to really high temperatures. There will also be no price advantage.

I have a strong personal bias against methanizers but if you are only looking for the three constituents this combination should work very well for you. If you are looking for other constituents you may need to re-think detectors a little bit.

I would also strongly recommend a sampling valve instead of splitless/split injection port and syringes. Much better sampling reproducibility.

Best regards.