Improvement of the inverse-gated-decoupling sequence for a faster quantitative analysis of various samples by 13C NMR spectroscopy.
The inverse-gated-decoupling sequence enables quantitative (1)H decoupled (13)C spectra to be obtained. We modified this sequence so as to obtain the same result in less time for molecules containing carbons with various relaxation properties. For that, we determined the optimal (13)C longitudinal-magnetization initial value for a faster relaxation while (1)H decoupler is stopped. This value can be calculated precisely via the nuclear Overhauser effects, the longitudinal relaxation times, together with the determination of the relaxation rate constants of carbons while (1)H are out of equilibrium. A supplementary delay of (1)H decoupling and/or a series of selective pulses applied at the beginning of the recovery delay allow an acceleration of (13)C longitudinal relaxation. We applied this method to the molecule of vanillin. The simultaneous quantification of all carbons was carried out with a recovery delay divided by two compared to the usual sequence.
Giraudeau
Patrick
P
Laboratoire d'Analyse Isotopique et Electrochimique de Métabolismes, UMR CNRS 6006, Université de Nantes, B.P. 92208, 2 rue de la Houssinière, F-44322 Nantes Cedex 03, France.
Baguet
Evelyne
E
D001547:Benzaldehydes / Q000737:chemistry*; D002247:Carbon Isotopes; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*
D001547:Benzaldehydes; D002247:Carbon Isotopes; C100058:vanillin