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Accurate Quantification of 45 N 2 O with a Membrane Inlet Mass Spectrometer by Optimizing the Temperature of a Cold Trap

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Membrane Inlet Mass Spectrometry (MIMS) is extensively applied in the study of nitrogen cycling processes. However, robust methods for the quantitative detection of N 2 O by this technique are still scarce. In this study, acidified azide was employed to reduce 15 NO 2 – to generate 45 N 2 O, which was used to make a standard curve for qualifying 45 N 2 O with MIMS. Key parameters affecting the azide reduction, including reagent concentration, reaction time, reaction mode, and salinity, were systematically evaluated and optimized. Then, the generated 45 N 2 O dissolved in water was introduced into the MIMS via a cold trap maintained at −88 ± 2 °C. This specific temperature capitalizes on the difference in the freezing points of N 2 O (−91 °C) and CO 2 (−78 °C), thereby effectively minimizing CO 2 interference during N 2 O measurement. Under optimized conditions, the linear fitting between 45 N 2 O ion current intensity and expected 45 N 2 O concentration showed an excellent linearity in the range of 0.1–100 μmol/L ( R 2 = 0.998), with a detection limit of 0.1 μmol/L. This method achieves accurate (relative error: 4.688%) and precise (relative standard deviation: 1.560%) detection of 45 N 2 O and holds potential for future application in tracing microbial N 2 O source–sink processes across diverse habitats.

Source: JACS Au

DOI: 10.1021/jacsau.5c01146