A novel high-temperature combustion based system for stable isotope analysis of dissolved organic carbon in aqueous samples. II: optimization and assessment of analytical performance

作者：Kirkels F M S A; Cerli C; Federherr E; Gao J; Kalbitz K^*

来源：Rapid Communications in Mass Spectrometry, 2014, 28(23): 2574-2586.

DOI：10.1002/rcm.7053

RATIONALE: Dissolved organic carbon (DOC) plays an important role in carbon cycling, making precise and routine measurement of delta C-13 values and DOC concentration highly desirable. A new promising system has been developed for this purpose. However, broad-scale application of this new technique requires an in-depth assessment of analytical performance, and this is described here. %26lt;br%26gt;METHODS: A high-temperature combustion Total Organic Carbon analyzer was interfaced with continuous flow isotope ratio mass spectrometry (TOC/IRMS) for the simultaneous analysis of the bulk DOC concentration and delta C-13 signature. The analytical performance (precision, memory effects, linearity, volume/concentration effects, accuracy) was thoroughly evaluated, including realistic and challenging conditions such as low DOC concentrations and natural DOC. %26lt;br%26gt;RESULTS: High precision (standard deviation, SD predominantly %26lt;= 0.15 parts per thousand) and accuracy (R-2 = 0.9997) were achieved for the delta C-13 analysis of a broad diversity of DOC solutions. Simultaneously, good results were obtained for the measurement of DOC concentration. Assessment of natural abundance and slightly C-13-enriched DOC, a wide range of concentrations (similar to 0.2-150 mgC/L) and injection volumes (0.05-3 mL), demonstrated minor/negligible memory effects, good linearity and flexible usage. Finally, TOC/IRMS was successfully applied to determine low DOC concentrations (%26lt;2 mgC/L) and DOC from diverse terrestrial, freshwater and marine environments (SD %26lt;= 0.23 parts per thousand). %26lt;br%26gt;CONCLUSIONS: TOC/IRMS enables fast and reliable measurement of DOC concentrations and delta C-13 values in aqueous samples, without pre-concentration and freeze-drying. Further investigations should focus on complex, saline matrices and very low DOC concentrations, to achieve a potential lower limit of 0.2 mgC/L. Thus, TOC/IRMS will give DOC research in terrestrial and aquatic environments a huge impulse with high-resolution, routine delta C-13 analysis.

• 出版日期2014-12-15