A novel high-temperature combustion based system for stable isotope analysis of dissolved organic carbon in aqueous samples. I: development and validation.

RATIONALE Traditionally, dissolved organic carbon (DOC) stable isotope analysis (SIA) is performed using either offline sample preparation followed by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS) or a wet chemical oxidation (WCO)-based device coupled to an isotope ratio mass spectrometer. The first method is time-consuming and laborious. The second involves the risks of underestimation of DOC concentration and isotopic fractionation due to incomplete oxidation. The development of an analytical method for accurate and sensitive DOC SIA is described in this study. METHODS A high-temperature combustion (HTC) system improves upon traditional methods. A novel total organic carbon (TOC) system, specially designed for SIA, was coupled to an isotope ratio mass spectrometer. An integrated purge and trap technique (peak focusing), flexible injection volume (0.05-3 mL), favorable carrier gas flow, modified ash crucible, new design of combustion tube and optimized drying system were used to achieve the necessary performance. RESULTS The system can reliably measure concentrations up to 1000 mgC/L. Compounds resistant to oxidation, such as barbituric acid, melamine and humic acid, were analyzed with recovery rates of 100 ± 1% proving complete oxidation. In this initial testing, the δ(13) C values of these compounds were determined with precision and trueness of ≤ 0.2‰ even with 3.5% salinity. Further tests with samples with low DOC concentrations resulted in LOQSIA method values of 0.5 mgC/L and 0.2 mgC/L for LOQSIA instr , considering an accuracy of ± 0.5‰ as acceptable. CONCLUSIONS The novel HTC system coupled to an isotope ratio mass spectrometer resulted in significantly improved sensitivity. The system is suitable for salt-containing liquids and compounds that are resistant to oxidation, and it offers a large concentration range. A second paper (which follows this one in this issue) will present a more comprehensive assessment of the analytical performance with a broad set of solutions and real samples. This highly efficient TOC stable isotopic analyzer will probably open up new possibilities in biogeochemical carbon cycle research.

[1]  J. Gao,et al.  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. , 2014, Rapid communications in mass spectrometry : RCM.

[2]  F. Grassa,et al.  Stable carbon isotope analysis of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in natural waters--results from a worldwide proficiency test. , 2013, Rapid communications in mass spectrometry : RCM.

[3]  T. Schmidt,et al.  Compound-specific Stable Isotope Analysis , 2012 .

[4]  W. Timms,et al.  Measuring dissolved organic carbon δ13C in freshwaters using total organic carbon cavity ring-down spectroscopy (TOC-CRDS) , 2012, Environmental Chemistry Letters.

[5]  T. Schmidt,et al.  High-temperature reversed-phase liquid chromatography coupled to isotope ratio mass spectrometry. , 2011, Rapid communications in mass spectrometry : RCM.

[6]  P. Albéric.  Liquid chromatography/mass spectrometry stable isotope analysis of dissolved organic carbon in stream and soil waters. , 2011, Rapid communications in mass spectrometry : RCM.

[7]  Aleš Fajgelj,et al.  Metrological traceability of measurement results in chemistry: Concepts and implementation (IUPAC Technical Report) , 2011 .

[8]  Stephen R. Parker,et al.  Diel biogeochemical processes and their effect on the aqueous chemistry of streams: A review , 2011 .

[9]  Klaus Kaiser,et al.  Dissolved carbon leaching from soil is a crucial component of the net ecosystem carbon balance , 2011 .

[10]  S. Barker,et al.  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. , 2010, Rapid communications in mass spectrometry : RCM.

[11]  Y. Gélinas,et al.  Coupling a high-temperature catalytic oxidation total organic carbon analyzer to an isotope ratio mass spectrometer to measure natural-abundance delta13C-dissolved organic carbon in marine and freshwater samples. , 2008, Analytical chemistry.

[12]  Christopher L. Osburn,et al.  The use of wet chemical oxidation with high‐amplification isotope ratio mass spectrometry (WCO‐IRMS) to measure stable isotope values of dissolved organic carbon in seawater , 2007 .

[13]  R. Houghton.  Balancing the Global Carbon Budget , 2007 .

[14]  M. Lilley,et al.  A method to measure the isotopic (13C) composition of dissolved organic carbon using a high temperature combustion instrument , 2007 .

[15]  Bertil Magnusson,et al.  Understanding the meaning of accuracy, trueness and precision , 2007 .

[16]  S. Bouillon,et al.  A new automated setup for stable isotope analysis of dissolved organic carbon , 2006 .

[17]  H. Gandhi,et al.  Isotopic ((13)C) analysis of dissolved organic carbon in stream water using an elemental analyzer coupled to a stable isotope ratio mass spectrometer. , 2004, Rapid communications in mass spectrometry : RCM.

[18]  Stephen L. R. Ellison,et al.  Harmonized guidelines for single-laboratory validation of methods of analysis (IUPAC Technical Report) , 2002, Chemistry International.

[19]  Ji‐Hyung Park,et al.  Controls on the dynamics of dissolved organic matter in soils: a review. , 2000 .

[20]  C. Hopkinson,et al.  Analysis of marine DOC using a dry combustion method , 1996 .

[21]  M. Thompson,et al.  Harmonized guidelines for internal quality control in analytical chemistry laboratories (Technical Report) , 1995 .

[22]  G. Aiken.  Chloride interference in the analysis of dissolved organic carbon by the wet oxidation method , 1992 .

[23]  P. Hall,et al.  A statistical justification to relating interlaboratory coefficients of variation with concentration levels , 1989 .

[24]  David T. Williams,et al.  Effects of sampling, shipping, and storage on total organic carbon levels in water samples , 1979, Bulletin of environmental contamination and toxicology.

[25]  B. Eadie,et al.  Some observations on the stable carbon isotope composition of dissolved and particulate organic carbon in the marine environment , 1978 .

[26]  P. M. Williams.  Stable Carbon Isotopes in the Dissolved Organic Matter of the Sea , 1968, Nature.

[27]  Julia Kluge,et al.  Handbook Of Stable Isotope Analytical Techniques , 2016 .

[28]  W. Brand.  Mass spectrometer hardware for analyzing stable isotope ratios , 2004 .

[29]  Dennis A. Hansell,et al.  Biogeochemistry of marine dissolved organic matter , 2002 .

[30]  J. Hedges.  Chapter 1 – Why Dissolved Organics Matter , 2002 .

[31]  Dennis A. Hansell,et al.  Marine dissolved organic matter and the carbon cycle , 2001 .

[32]  B. Peterson,et al.  Platinum-catalyzed combustion of DOC in sealed tubes for stable isotopic analysis , 1993 .

[33]  P. Wangersky.  Dissolved organic carbon methods: a critical review , 1993 .

[34]  The amazing Horwitz function , 2022 .