Analysis of Nitrous Oxide and Helium in Air: Greenhouse Gas Inventory

We have developed an analytical method using gas a chromatograph equipped with a pulsed discharge detector (GC-PDD) that is capable of analyzing nitrous oxide (N2O) from 50 ppbv up to 500 ppmv. Samples are collected in 4-layer metalized gas sampling bags. Total time of analysis is 17 minutes, and no appreciable interference from water or CO2has been observed.To measure dissolved N2O, an equilibrium headspace method was developed. The headspace N2O gas was analyzed by GC-PDD, and this result was converted into the corresponding dissolved N2O concentration. The approximate calibration range of dissolved N2O is from 0.002 μg/mL to 22 μg/mL.A method for analysis of helium in air was developed using a gas chromatograph equipped with a microvolume thermal conductivity detector (TCD). The quantifiable range ran from 5 ppmv (the ambient air level) up to 12,000 ppmv using two calibration curves.