We have some ag-scientists who are monitoring the nitrous oxide emissions from soil. Literature studies cite ecd as the detector for gc analysis. Scotts gas analysts say a 3 mL sample loop will give them 500 ppb detection limits. I want to try a npd detector. Anyone know why ecd would be the detector-of-choice - not npd?

Try it and tell us what happens. I think NPD for nitrous oxide will give no more response than nitrogen, ie. zero - but what do I know - I never tried NPD for nitrous oxide and never considered it for a second. Perhaps I am missing something. I agree with Scott on the sensitivity of ECD. I find the dynamic range is about 3-300 ng nitrous oxide at the detector, but the top half of that range is not linear on my Perkin Elmer XL ECD. The detector temperature is a significant factor. Raising the temperature increases sensitivity. Since the background ambient level of N2O is only just detectable with a normal sample loop your ag- colleagues may have to consider trapping say 100 ml air on a Mol Sieve 5A sorbent cartridge and heating it to release the adsorbed N2O.

The rubidium bead NP detectors that I have worked with depend on a C-N bond being present so nitrous oxide would not be expected to respond.

However the Varian/OI pulsed flame photometric detector will - see http://www.tau.ac.il/chemistry/amirav/pfpd.shtml

I have one but have not used it for this application

Regards,

Ralph