RAPID ISOTOPIC ANALYSIS OF TRACE GASES AT ATMOSPHERIC LEVELS

A method is reported allowing simultaneous isotopic analysis of N2 and N2O at atmospheric concentrations. A gas chromatograph fitted with a thermal conductivity detector and micro desorption trap was interfaced to an isotope ratio mass spectrometer (Tracer Mass, Europa Scientific, Crewe, UK). CO2 and H2O were chemically removed prior to the complete sorption of N2O onto a zeolite bed. N2 was chromatographically purified prior to isotopic analysis. The N2O Was thermally desorbed into a slow carrier stream (300 muL min-1) prior to analysis at m/z 44, 45 and 46. Precision of measurement was 0.3663 +/- 0.000013 and 0.365 +/- 0.0025 Atom % N-15 as N2 and N2O respectively. The method was then evaluated for a soil denitrification experiment.