High precision laser-based N2O isotopologue analyser for environmental applications.

Nitrate contamination in water sources is a growing concern, primarily caused by agricultural runoff, animal manure, and wastewater. This pollution leads to severe environmental issues such as lake eutrophication and oceanic dead zones, impacting tourism and fisheries. It also poses significant public health risks due to elevated nitrate levels in drinking water. Stable isotopologues of N₂O (δ¹⁵N, δ¹⁸O, and δ¹⁷O) in nitrates serve as excellent tracers for distinguishing between anthropogenic sources of nitrate pollution. Understanding variations in isotopologue composition enables targeted strategies to mitigate these harmful effects^[1],[2].

Conventional methods for isotopologue analysis require chemical conversion of nitrates to refined salts (KNO₃) or N₂O gas, followed by EA-IRMS or GC-IRMS measurements. These techniques are time-consuming, involve toxic chemicals, and, in the case of GC-IRMS, require cryogenic purge-and-trap steps. While IRMS remains the gold standard, its workflow is tedious and only provides limited throughput.

We present an automated, laser-based solution for simultaneous measurement of N₂O isotopologues with high precision and repeatability. The GLA451-N2OI3 spectrometer, based on ABB’s patented Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) technology^[3], achieves precisions of 0.3 ‰ (δ¹⁵N), 0.5 ‰ (δ¹⁸O), and 3 ‰ (δ¹⁷O) at 2 ppm N₂O with a 300 seconds integration time. OA-ICOS offers excellent long-term stability and a wide linear dynamic range.

A key advantage of the GLA451-N2OI3 is its compatibility with a headspace autosampler; enabling fully automated analysis of N₂O derived from nitrates at high throughput—up to 140 samples in 24 hours. The autosampler uses a 5 mL syringe for up to 15 mL injections (3 × 5 mL). Tests with 10 ppm N₂O demonstrate repeatability of 1.5 ‰ across 36 injections, further improved to <1 ‰ with drift and reference corrections^[1].

In this presentation we demonstrate the simplicity, precision and accuracy of ABB’s OA-ICOS technology, offering a robust and user-friendly spectrometer to measure the triple isotopologues of nitrate. Crucially, its unique direct δ¹⁷O measurement capability provides the full triple-isotope fingerprint, including Δ¹⁷O-excess, which is critical for distinguishing atmospheric nitrate sources.  Collectively, these advancements make the GLA451-N2OI3 an invaluable tool for environmental and analytical scientists, empowering high-resolution monitoring, atmospheric nitrogen research and water quality assessments with unprecedented confidence and efficiency.

References

[1]         L. I. Wassenaar, , et. al, ‘Automated rapid triple-isotope (δ15N, δ18O, δ17O) analyses of nitrate by Ti(III) reduction and N2O laser spectrometry’, Isotopes Environ. Health Stud., vol. 59, no. 3, pp. 297–308, May 2023, doi: 10.1080/10256016.2023.2222222.

[2]         C. W. Kreitler, ‘Determining the source of nitrate in groundwater by nitrogen isotope studies’, 1974, Accessed: Jan. 09, 2026. [Online]. Available: http://hdl.handle.net/2152/65451

[3]         D. S. Baer, et. al, ‘Sensitive absorption measurements in the near-infrared region using off-axis integrated cavity output spectroscopy’, vol. 4817.