An improved GC-ECD method for measuring atmospheric N2O

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.