Internal Referencing for ^sup 13^C Position-Specific Isotope Analysis Measured by NMR Spectrometry

• Published in: Analytical chemistry (Washington) 2015-08, Vol.87 (15), p.7550
• Main Authors: Bayle, Kevin, Grand, Mathilde, Chaintreau, Alain, Robins, Richard J, Fieber, Wolfgang, Sommer, Horst, Akoka, Serge, Remaud, Gérald S
• Format: Article
• Language: English
• Subjects: Biochemistry; Isotopes; Mass spectrometry; Molecules; NMR; Nuclear magnetic resonance
• ISSN: 0003-2700; 1520-6882

The intramolecular 13C 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 13C NMR spectrometry (irm-13C NMR) is a generic method that offers the potential to conduct 13C position-specific isotope analysis with a precision better than 1... Until now, determining absolute values also required measurement of the global (or bulk) 13C composition (...) by mass spectrometry. In a radical new approach, it is shown that an internal isotopic chemical reference for irm-13C NMR can be used instead. The strategy uses 1H 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 1H NMR which produces signal distortion and alters quantification. The methodology, applied to vanillin with dimethylsulfone as an internal standard, has an equivalent accuracy (