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Stable isotope analysis of dissolved organic carbon in soil solutions using a catalytic combustion total organic carbon analyzer‐isotope ratio mass spectrometer with a cryofocusing interface
Author(s) -
De Troyer I.,
Bouillon S.,
Barker S.,
Perry C.,
Coorevits K.,
Merckx R.
Publication year - 2010
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.4403
Subject(s) - chemistry , carbon fibers , combustion , isotopes of carbon , environmental chemistry , isotope ratio mass spectrometry , total organic carbon , soil carbon , isotope , catalysis , mass spectrometry , spectrum analyzer , analytical chemistry (journal) , soil water , organic chemistry , chromatography , soil science , environmental science , materials science , physics , quantum mechanics , composite number , composite material , electrical engineering , engineering
Stable carbon isotopes are a powerful tool to assess the origin and dynamics of carbon in soils. However, direct analysis of the 13 C/ 12 C ratio in the dissolved organic carbon (DOC) pool has proved to be difficult. Recently, several systems have been developed to measure isotope ratios in DOC by coupling a total organic carbon (TOC) analyzer with an isotope ratio mass spectrometer. However these systems were designed for the analysis of fresh and marine water and no results for soil solutions or 13 C‐enriched samples have been reported. Because we mainly deal with soil solutions in which the difficult to oxidize humic and fulvic acids are the predominant carbon‐containing components, we preferred to use thermal catalytic oxidation to convert DOC into CO 2 . We therefore coupled a high‐temperature combustion TOC analyzer with an isotope ratio mass spectrometer, by trapping and focusing the CO 2 cryogenically between the instruments. The analytical performance was tested by measuring solutions of compounds varying in the ease with which they can be oxidized. Samples with DOC concentrations between 1 and 100 mg C/L could be analyzed with good precision (standard deviation (SD) ≤0.6‰), acceptable accuracy, good linearity (overall SD = 1‰) and without significant memory effects. In a 13 C‐tracer experiment, we observed that mixing plant residues with soil caused a release of plant‐derived DOC, which was degraded or sorbed during incubation. Based on these results, we are confident that this approach can become a relatively simple alternative method for the measurement of the 13 C/ 12 C ratio of DOC in soil solutions. Copyright © 2010 John Wiley & Sons, Ltd.