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Position‐specific 15 N isotope analysis in organic molecules: A high‐precision 15 N NMR method to determine the intramolecular 15 N isotope composition and fractionation at natural abundance
Author(s) -
Joubert Valentin,
Silvestre Virginie,
Lelièvre Maxime,
Ladroue Virginie,
Besacier Fabrice,
Akoka Serge,
Remaud Gérald S.
Publication year - 2019
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4903
Subject(s) - chemistry , isotopomers , isotope , analytical chemistry (journal) , kinetic isotope effect , mass spectrometry , nuclear magnetic resonance spectroscopy , nmr spectra database , stable isotope ratio , fractionation , isotope fractionation , intramolecular force , deuterium , molecule , spectral line , chromatography , stereochemistry , organic chemistry , physics , astronomy , quantum mechanics
The position‐specific 15 N isotope content in organic molecules, at natural abundance, is for the first time determined by using a quantitative methodology based on 15 N Nuclear Magnetic Resonance (NMR) spectrometry. 15 N NMR spectra are obtained by using an adiabatic “Full‐Spectrum” INEPT sequence in order to make possible 15 N NMR experiments with a high signal‐to‐noise ratio (>500), to reach a precision with a standard deviation below 1‰ (0.1%). This level of precision is required for observing small changes in 15 N content associated to 15 N isotope effects. As an illustration, the measurement of an isotopic enrichment factor ε for each 15 N isotopomer is presented for 1‐methylimidazole induced during a separation process on a silica column. The precision expressed as the long‐term repeatability of the methodology is good enough to evaluate small changes in the 15 N isotope contents for a given isotopomer. As observed for 13 C, inverse and normal 15 N isotope effects occur concomitantly, giving access to new information on the origin of the 15 N isotope effects, not detectable by other techniques such as isotope ratio measured by Mass Spectrometry for which bulk (average) values are obtained.