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.

Adsorption Studies on Heterogeneous Titania 3587 closer proximity of neighboring Pd atoms in the transition state, which would improve the agreement. The value of v for the -phase could be significantly different from the /3-phase value used here, although a-phase isotherm data coupled with a statistical mechanical model yield a value of v close to that used here. 18 Recently, Makrides8 has evaluated D0 from Zener's absolute rate theory treatment of interstitial diffusion.23 In this somewhat different treatment to that given here, D0 was estimated from the elastic constants of Pd metal and a measured activation energy with an assumed simple sinusoidal potential energy function. The value obtained is slightly less than twice that calculated here.8

Rationale Wet chemical oxidation combined with isotope ratio mass spectrometry has become a routine technique for analyzing the stable carbon isotope composition of dissolved organic (DOC) and inorganic (DIC) carbon. However, methodological inconsistencies between laboratories in using different reference materials lead to a discrepancy in results. We experimentally tested the precision and accuracy of the analysis of commonly available international reference materials and other chemicals potentially suitable for laboratory standards. Methods The solid international reference materials and other simple chemicals were used to prepare water solutions. A range of carbon concentrations was chosen to optimize tests for (1) precision and accuracy, (2) linearity, (3) detection limits, (4) memory effects, and (5) efficiency of DIC removal from a DOC/DIC mixtures. Samples were analyzed using an LC‐IsoLink coupled with a Delta V Plus isotope ratio mass spectrometer (Thermo Fisher Scientific). Results The analytical setup had a negligible memory effect, good reproducibility (<0.21‰) and accuracy (maximum difference from the true values <0.35‰) for the analyzed organic compounds if approximately ≥9 × 10−09 moles of dissolved carbon was injected into the system (~11 mg C L−1 if a 10‐μL loop was used). Analyses of sodium bicarbonate or calcium carbonate solutions had a two‐fold lower accuracy despite maintaining a high precision. Conclusions Aqueous solutions of international reference materials such as L‐glutamic acids (USGS40, USGS41), benzoic acid (IAEA‐601) and sucrose (IAEA‐CH‐6) can be successfully used for direct normalization of results to the VPDB scale. By contrast, analyses of caffeine and urea returned very reproducible but highly inaccurate results and these materials are not recommended for standards.