Isotopically characterised N₂ O reference materials for use as community standards.

Area of Science:

• Environmental Science
• Analytical Chemistry
• Isotope Geochemistry

Background:

• Understanding nitrous oxide (N2O) sources and sinks relies on its isotopic composition.
• Advancements in mass spectrometry and laser spectroscopy for N2O analysis require reliable isotope reference materials (RMs).

Purpose of the Study:

• To develop and characterize a set of N2O isotope reference materials (RMs).
• To establish robust N2O isotope reference scales for improved source apportionment and analytical accuracy.

Main Methods:

• Seven pure N2O isotope RMs were synthesized and analyzed for 15N/14N, 18O/16O, 17O/16O ratios, and 15N site preference (SP).
• Specialized laboratories performed analyses, focusing on site-specific isotopic composition, linking measurements to existing isotope reference materials.

Main Results:

• The N2O RMs exhibit a wide range of delta (δ) values: δ15N (0 to +104‰), δ18O (+39 to +155‰), and δ15NSP (-4 to +20‰).
• Robust estimates for δ15N(N2O) and δ18O(N2O) were achieved with uncertainties of ~0.05‰ and ~0.15‰, respectively.
• An offset of >1.5‰ was detected for δ15NSP compared to previous calibrations, highlighting the need for further investigation.

Conclusions:

• A set of seven N2O isotope RMs anchored to international scales was successfully developed.
• These RMs will facilitate the implementation of recommended two-point calibration and improve data quality for N2O isotope analysis.
• The availability of δ17O data is expected to enhance δ15NSP and δ15N measurements, fostering inter-laboratory compatibility and research advancement.