Methodological Recommendations for Water Isotope Measurements Using CRDS: Balancing Throughput and Precision

Cavity Ring-Down Spectroscopy (CRDS) has emerged as a critical tool for measuring water isotopes in climate, environmental, and hydrological research. Key features of CRDS analyzers, such as the L2130-i and L2140-i, include high precision, minimal drift, and field deployability. However, the precision and accuracy requirements of water isotope measurements vary by application. For example, paleoclimate studies demand the highest precision (on par with IRMS), while other applications prioritize rapid analysis of large sample sets over precision.

In this study, we present updated methodological recommendations for water isotope analysis using CRDS, tailored to different precision, accuracy, and throughput requirements. We evaluated a range of analytical and data processing methods using the WICO 2024 sample set. This set, provided by the IAEA, includes six water samples with δ¹⁸O values ranging from -22‰ to +1‰ and δ²H values spanning from -163‰ to +17‰. The samples were analyzed on a Picarro L2130-i instrument in both Standard and Express mode [1]. Data were processed using the analyzer's built-in ChemCorrect software and the open-source FLIIMP software [2], which enables advanced data correction techniques such as drift and memory correction.

Our findings highlight the trade-offs between precision and throughput for different use cases and underscore the importance of selecting appropriate analysis and processing methods based on specific research needs.

References

[1] Galili, N. et al. (2025). Cavity Ring-Down Spectroscopy Performance and Procedures for High-Throughput δ¹⁸O and δ²H Measurement in Water Using “Express” Mode. Applied Spectroscopy.

[2] Sodemann, H. et al. (2023). FLIIMP - a community software for the processing, calibration, and reporting of liquid water isotope measurements on cavity ring-down spectrometers. MethodsX, 11, 102297.