An improved GC-ECD method for measuring atmospheric N2O

Abstract

Gas chromatography equipped with an electron capture detector (GC-ECD) has been widely used for measuring atmospheric N2O, but nonlinear response and the influence of atmospheric CO2 have been recognized as defects for quantification. An original GC-ECD method using N2 as carrier gas was improved by introducing a small flow rate of CO2 makeup gas into the ECD, which could well remedy the above defects. The N2O signal of the improved method was 4-fold higher than that of the original method and the relative standard deviation was reduced from > 1% to 0.31%. N2O concentrations with different CO2 concentrations (172.2 × 10−6–1722 × 10−6 mol/mol) measured by the improved GC-ECD method were in line with the actual N2O concentrations. However, the N2O concentrations detected by the original method were largely biased with a variation range of –4.5%∼7%. The N2O fluxes between an agricultural field and the atmosphere measured by the original method were greatly overestimated in comparison with those measured by the improved method. Good linear correlation (R2 = 0.9996) between the response of the improved ECD and N2O concentrations (93 × 10−9–1966 × 10−9 mol/mol) indicated that atmospheric N2O could be accurately quantified via a single standard gas. Atmospheric N−2O concentrations comparatively measured by the improved method and a high precision GC-ECD method were in good agreement.