Isotope Ratio Monitoring by NMR. Part 1: Recent Advances
Résumé
Many physical and chemical processes in living systems are accompanied byisotopic fractionation on common atoms. The determination of isotopic abundanceis therefore an unrivaled method to probe the (bio)chemical origin ofnatural or synthetic molecules. NMR has become a major analytical techniquein stable isotope analysis, since SNIF-NMR (site-specific natural isotopic fractionationstudied by nuclear magnetic resonance) was introduced by Profs. Martinand Martin in the 1980s. Renamed irm-NMR (isotopic ratio measurement byNMR), it is a major authentication tool and has been recognized as an officialmethod to detect subtle food adulteration. It is the only generic analyticaltechnique that can quantify each isotopomer without degradation; it thereforeprovides significant additional information in the many cases in which theaverage isotopic distribution is insufficient to differentiate samples from differentorigins and/or to understand (bio)synthetic pathways. In the last 30 years,irm-NMR has undergone numerous methodological developments, which haveextended its field of application. In particular, its extension to 13C isotopic NMRand to anisotropic 2H NMR has widened the range of samples that can be studied.This chapter describes the general principles of irm-NMR and highlights therecent methodological developments (reference methods, pulse sequences) andthe original applications stemming from these advances. Lastly, perspectives arediscussed, based on some of these most recent methodological advances in NMR.