Design of a Quantitative DEPT NMR Experiment for Carbon-13 Acquisitions

摘要

A scheme has been developed to eliminate virtually all signal intensity dependence on lJCH in polarization transfers between 'H and Carbon-13 nuclei, reducing the differences in signal intensity to only l .5% over the entire natural IJQ range. The scheme relics on the summation of time-domain data acquired with four suitably selected delta delays so that the J dependence is essentially cancelled in the final signal averaged free induction decay. These A delays have been incorporated into the DEPT pulse sequence to create sensitivity-enhanced experiments for collecting quantitative Carbon-13 ('H) spectra. Four experiments, each with unique read pulse angles, give quantitative spectra with 200-300% more sensitivity than conventional Carbon-13 spectra acquired with inverse-gated 'H decoupling. The experiments are ideal for recording spectra with improved quantitative information or for substantially reducing the long acquisition times indicative of quantitative C experiments. The ability of the experiments to provide quantitative spectra was demonstrated with a simple ethylbenzene solution; however, they can easily be adapted to various applications for analysis of complex mixtures.