Improvement of the inverse-gated-decoupling sequence for a faster quantitative analysis by 13C NMR

The inverse-gated-decoupling sequence enables quantitative H-1 decoupled C-13 spectra to be obtained. We modified this sequence so as to obtain the same result in less time. For that, we determined the optimal C-13 longitudinal-magnetisation initial value for a faster relaxation while H-1 decoupler is stopped. This value can be calculated via the longitudinal relaxation times and the nuclear Overhauser effects. For a given nucleus, a supplementary delay of H-1 decoupling and/or a pulse at the beginning of the recovery delay allows an acceleration of the C-13 longitudinal relaxation. We checked this result on the molecule of N,N-dimethylacetamide. A simultaneous quantitative analysis of all carbons was carried out with a recovery delay divided by four compared to the Usual sequence.