title: Internal Referencing for ¹³C Position-Specific Isotope Analysis Measured by NMR Spectrometry.
abstract: The intramolecular (13)C composition of a molecule retains evidence relevant to its (bio)synthetic history and can provide valuable information in numerous fields ranging from biochemistry to environmental sciences. Isotope ratio monitoring by (13)C NMR spectrometry (irm-(13)C NMR) is a generic method that offers the potential to conduct (13)C position-specific isotope analysis with a precision better than 1‰. Until now, determining absolute values also required measurement of the global (or bulk) (13)C composition (δ(13)Cg) by mass spectrometry. In a radical new approach, it is shown that an internal isotopic chemical reference for irm-(13)C NMR can be used instead. The strategy uses (1)H NMR to quantify both the number of moles of the reference and of the studied compound present in the NMR tube. Thus, the sample preparation protocol is greatly simplified, bypassing the previous requirement for precise purity and mass determination. The key to accurate results is suppressing the effect of radiation damping in (1)H NMR which produces signal distortion and alters quantification. The methodology, applied to vanillin with dimethylsulfone as an internal standard, has an equivalent accuracy (<1‰) to that of the conventional approach. Hence, it was possible to clearly identify vanillin from different origins based on the (13)C isotopic profiles.
authors.affiliation: †EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modeling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3, France.
authors.forename: Kevin
authors.initials: K
authors.lastname: Bayle
authors.affiliation: †EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modeling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3, France.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Grand
authors.forename: Alain
authors.initials: A
authors.lastname: Chaintreau
authors.affiliation: †EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modeling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3, France.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Robins
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Fieber
authors.forename: Horst
authors.initials: H
authors.lastname: Sommer
authors.affiliation: †EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modeling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3, France.
authors.forename: Serge
authors.initials: S
authors.lastname: Akoka
authors.affiliation: †EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modeling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3, France.
authors.forename: Gérald S
authors.initials: GS
authors.lastname: Remaud