Department of Nuclear Sciences and Applications, Division of Physical and Chemical Sciences, Isotope Hydrology Laboratory, International Atomic Energy Agency, Vienna, Austria.
Rapid Commun Mass Spectrom. 2021 Dec 30;35(24):e9193. doi: 10.1002/rcm.9193.
Stable isotope analyses of environmental waters (δ H, δ O) are an important assay in hydrology and environmental research with rising interest in δ O, which requires ultra-precise assays. We evaluated isotope analyses of six test water samples for 281 laboratory submissions measuring δ H and δ O along with a subset analyzing δ O and Δ O by laser spectrometry and isotope ratio mass spectrometry (IRMS).
Six test waters were distributed to laboratories spanning a wide δ range of natural waters for δ H, δ O and δ O and Δ O. One sample was a blind duplicate to test reproducibility and claims of analytical precision.
Results showed that ca 83% of the submissions produced acceptable δ O and δ H results within 0.2‰ (mUr) and 1.6‰ of the benchmark values, respectively. However, 17% of the submissions gave questionable to unacceptable results. A blind duplicate revealed many laboratories reported overly optimistic precision, and many could not replicate within their claimed precision. For Δ O, dual-inlet results for IRMS using quantitative O conversion were accurate and highly precise, but the results for laser spectrometry ranged by ca 200 per meg (μUr) for each sample, with ca 70% unable to replicate the duplicate to their claimed Δ O precision. One complicating factor is the lack of certified primary reference waters for δ O.
No single factor or combination of factors was identifiable for poor or good performance, and underperformance came from issues like data normalization including inadequate memory and drift corrections, compromised working reference materials and underperforming instrumentation. We recommend isotope laboratories include high and low δ value controls of known isotope composition in each run. Progress in Δ O analyses by laser spectrometry requires extraordinary proof of performance claims and would benefit from the development of adoptable and systematic advanced data processing procedures to correct for memory and drift.
环境水的稳定同位素分析（δH、δO）是水文学和环境研究中的一项重要分析，对 δO 的兴趣日益增加，这需要超精确的分析。我们评估了 6 个测试水样的同位素分析结果，这些水样来自 281 个实验室的提交数据，其中包括 δH 和 δO 的分析，以及一小部分通过激光光谱法和同位素比质谱法（IRMS）分析 δO 和 ΔO。
将 6 个测试水分配给实验室，这些实验室涵盖了天然水的广泛 δ 范围，用于 δH、δO 和 δO 和 ΔO 的分析。其中一个样本是一个盲样重复，以测试重复性和分析精度的声称。
结果表明，约 83%的提交数据在 0.2‰（mUr）和基准值的 1.6‰范围内产生了可接受的 δO 和 δH 结果。然而，17%的提交数据结果存在疑问或不可接受。盲样重复表明，许多实验室报告的精度过于乐观，许多实验室无法在其声称的精度范围内复制。对于 ΔO，使用定量 O 转换的双入口 IRMS 结果准确且高度精确，但激光光谱法的结果每个样本相差约 200 个单位（μUr），约 70%的实验室无法复制其声称的 ΔO 精度。一个复杂的因素是缺乏 δO 的认证基准参考水。
没有单一因素或多种因素可以确定表现不佳或良好的原因，表现不佳的原因包括数据归一化问题，如记忆和漂移校正不充分、工作参考材料受损以及仪器性能不佳。我们建议同位素实验室在每次运行中包含已知同位素组成的高值和低值控制。激光光谱法在 ΔO 分析方面的进展需要非凡的性能证明，并且受益于开发可采用的和系统的先进数据处理程序来校正记忆和漂移。
