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Please use this identifier to cite or link to this item: http://drs.nio.org/drs/handle/2264/4193

Title: Online Stable Isotope Analysis of Dissolved Organic Carbon Size Classes Using Size Exclusion Chromatography Coupled to an Isotope Ratio Mass Spectrometer
Authors: Malik, A.
Scheibe, A.
LokaBharathi, P.A.
Gleixner, G.
Citation: Environmental Science & Technology, vol.46; 2012; 10123-10129
Issue Date: 2012
Publisher: American Chemical Society
Abstract: Stable isotopic content of dissolved organic carbon (delta sup(13)C-DOC) provides valuable information on its origin and fate. In an attempt to get additional insights into DOC cycling, we developed a method for delta sup(13)C measurement of DOC size classes by coupling high-performance liquid chromatography (HPLC) - size exclusion chromatography (SEC) to online isotope ratio mass spectrometry (IRMS). This represents a significant methodological contribution to DOC research. The interface was evaluated using various organic compounds, thoroughly tested with soil–water from a C3-C4 vegetation change experiment, and also applied to riverine and marine DOC. delta sup(13)C analysis of standard compounds resulted in excellent analytical precision (less than or equal to 0.3 ppt). Chromatography resolved soil DOC into 3 fractions: high molecular weight (HMW; 0.4-10 kDa), low molecular weight (LMW; 50-400 Da), and retained (R) fraction. Sample reproducibility for measurement of delta sup(13)C-DOC size classes was plus or minus 0.25 ppt for HMW fraction, plus or minus 0.54 ppt for LMW fraction, and plus or minus 1.3 ppt for R fraction. The greater variance in delta sup(13)C values of the latter fractions was due to their lower concentrations. The limit of quantification (SD less than or equal to 0.6 ppt) for each size fraction measured as a peak is 200 ng C (2 mg C/L). delta sup(13)C-DOC values obtained in SEC mode correlated significantly with those obtained without column in the mu EA mode (p less than 0.001, intercept 0.17 ppt), which rules out SEC-associated isotopic effects or DOC loss. In the vegetation change experiment, fractions revealed a clear trend in plant contribution to DOC; those in deeper soils and smaller size fractions had less plant material. It was also demonstrated that the technique can be successfully applied to marine and riverine DOC without further sample pretreatment.
Document type: Journal Article
Copyright: Copyright [2010] American Chemical Society. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
URI: http://drs.nio.org/drs/handle/2264/4193
Appears in Collections:Chemical Sciences

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