Analytical model for site-specific isotope fractionation in ¹³C during sorption: Determination by isotopic ¹³C NMR spectrometry with vanillin as model compound

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• 作者：Patrick Hö ; hener^a ; ^{patrick.hohener@univ-provence.fr} ; Virginie Silvestre^b ; Anaï ; s Lefranç ; ois^b ; Denis Loquet^b ; Eliot P. Botosoa^b ; ¹ ; Richard J. Robins^b ; Gé ; rald S. Remaud^b
• 关键词：Stable isotopes ; Modeling ; Sorption ; Transport ; NMR
• 刊名：Chemosphere
• 出版年：2012
• 期刊代码：15_00456535
• 类别：env
• 出版时间：April, 2012
• 卷：87
• 期：5
• 页码：445-452
• 文件大小：513 K

摘要

The aim of this study was to conceive a reactive transport model capable of providing quantitative site-specific enrichment factors for fractionation in ¹³C isotopic content during sorption. As test compound the model treats vanillin, for which the ¹³C isotopic content at natural abundance at each of the 8 carbon positions can be measured by quantitative ¹³C nuclear magnetic resonance spectrometry. This technique determines the isotope ratios with a resolution better than 卤1鈥?(0.1%) at each carbon position. Site-specific isotope fractionations were recorded in chromatography column experiments with silica RP-18 as stationary phase. The one dimensional reactive transport model accounted for the sorption/desorption behavior of 8 individual ¹³C-isotopomers and one ¹²C-isotopomer of vanillin and reproduced satisfactorily the bulk (average over the whole compound) fractionation observed during elution. After model calibration, the enrichment factors were fitted for each carbon site where a significant fractionation was recorded. To show the interest of such a transport model for environmental studies, the model, extended to three dimensions, was exploited to simulate reactive transport in an aquifer. These results show that significant ¹³C isotope fractionation is expected for 4 out of 8 ¹³C-isotopomers in vanillin, and illustrate that bulk isotope ratios measured by conventional compound specific isotope analysis and mass spectrometry would hardly document significant isotope fractionations in vanillin. It is concluded that modeling of site-specific isotope ratios in molecules is a priori feasible and may help to quantify unknown processes in the environment.