West Australian Biogeochemistry Centre, School of Plant Biology, The University of Western Australia , MO90, 35 Stirling Highway, Crawley, Western Australia 6009, Australia.
Environ Sci Technol. 2014;48(5):2827-34. doi: 10.1021/es4049412. Epub 2014 Feb 17.
The analysis of the stable hydrogen and oxygen isotope composition of water using cavity ring-down spectroscopy (CRDS) instruments utilizing infrared absorption spectroscopy have been comprehensively tested. However, potential limitations of infrared spectroscopy for the analysis of highly saline water have not yet been evaluated. In this study, we assessed uncertainty arising from elevated salt concentrations in water analyzed on a CRDS instrument and the necessity of a correction procedure. We prepared various solutions of mixed salts and separate solutions with individual salts (NaCl, KCl, MgCl2, and CaCl2) using deionized water with a known stable isotope composition. Most of the individual salt and salt mixture solutions (some up to 340 g L(-1)) had δ-values within the range usual for CRDS analytical uncertainty (0.1‰ for δ (18)O and 1.0‰ for δ (2)H). Results were not compromised even when the total load of salt in the vaporizer reached ∼38.5 mg (equivalent to build up after running ∼100 ocean water samples). Therefore, highly saline mixtures can be successfully analyzed using CRDS, except highly concentrated MgCl2 solutions, without the need for an additional correction if the vaporizer is frequently cleaned and MgCl2 concentration in water is relatively low.
利用基于红外吸收光谱的腔衰荡光谱（CRDS）仪器对水的稳定氢和氧同位素组成进行分析已经得到了广泛的验证。然而，红外光谱法在分析高盐度水方面的潜在局限性尚未得到评估。在这项研究中，我们评估了在 CRDS 仪器上分析高盐度水时由盐浓度升高引起的不确定度以及是否需要校正程序。我们使用具有已知稳定同位素组成的去离子水制备了各种混合盐溶液和单独盐（NaCl、KCl、MgCl2和 CaCl2）溶液。大多数单独盐和盐混合溶液（有些高达 340 g/L）的 δ 值在 CRDS 分析不确定度的通常范围内（δ (18)O 为 0.1‰，δ (2)H 为 1.0‰）。即使蒸发器中的盐总负荷达到约 38.5 毫克（相当于运行约 100 个海水样品后的积累量），结果也没有受到影响。因此，如果蒸发器经常清洗且水中的 MgCl2浓度相对较低，则无需额外校正，即可成功使用 CRDS 分析高盐度混合物，除了高浓度的 MgCl2溶液。
