Can the Agilent 7890A with the ECD and FID only analyse CH4 and N2O gases. I hear theres need for an extra unit (Green house gas analyser) but without it is still possible to do the analysis?
Yes, it should work, but if you want to do it in parallel it is not easy. The competitor Shimadzu sells a dedicated N2O/CO/CO2/CH4 Analysis System based on ECD and FID only. It is a bit complex due to the fact that a total of 5 valves and 7 columns are used in this GC system. CO, Methane and CO2 are directed to a methanizer. A TCD would ease things.
For N20 alone see also Zhang et al.: An improved GC-ECD method for measuring atmospheric N2O. Journal of Environmental Sciences. Volume 25, Issue 3, 1 March 2013, Pages 547-553.
yes. There are a few options (if you need only to determine this two compounds):
1. You can use a splitter (3-way) after your column this way you can determine this compounds CH4 - on FID and N2O on ECD. The question is about concentration level of the analytes. To big concentration of N2O will cause saturation of ECD. I'm not sure if Agilent provides this option but other vendors (like Perkin Elmer) provide a range settings for ECD i.e. high and low sensitivity.
2. ECD is non destructive you can connect a gas-tight fitting to the outlet of ECD and the second end will be connected to FID inlet (the problem is the big make-up gas flow for ECD, which will dilute your sample and will affect FID sensitivity). For this compounds there will be no problems regarding condensation/sorption etc.
3. If you have two injectors you can use two channels separately for each compound