Determination of CH4, CO2 and N2O in air samples and soil atmosphere by gas chromatography mass spectrometry, GC-MS

A method for determination of the climate gases CH4, CO2 and N2O in air samples and soil atmosphere was developed using GC-MS. The method uses straightforward gas chromatography ( separation of the gases) with a mass spectrometric detector in single ion mode ( specific determination). The gases were determined with high sensitivity and high sample throughput (18 samples h(-1)). The LOD (3sigma) for the gases were 0.10 muL L-1 for CH4, 20 muL L-1 for CO2 and 0.02 muL L-1 for N2O. The linear range (R-2 = 0.999) was up to 500 muL L-1 for CH4, 4000 muL L-1 for CO2 and 80 mL L 21 for N2O. The samples were collected in 10 mL vials and a 5 mL aliquot was injected on column. The method was tested against certified gas references, the analytical data gave an accuracy within +/- 5% and a precision of +/- 3%. The presence of less than or equal to10% by volume of C2H2 ( often used experimentally to prevent N-2 formation from N2O) did not interfere with detection for the targeted trace gases.