This presentation summarizes progress in using NMR spectroscopy to measure 13C/12C stable isotope ratios in compounds of interest containing as few as one carbon atom, by making use of the 13C satellite peaks in 1-D 1H spectra. This is an appealingly simple approach: insofar as NMR is a quantitative technique that counts the spins being observed, the large one-bond 1H-13C coupling constant causes those protons attached to 13C to be well-separated from those attached to 12C. Therefore, quantitation of the number of protons attached to each carbon isotope is possible in principle. The difficulty in this approach arises from the small variation in 13C/12C for most compounds. And with two orders of magnitude difference in the areas of the satellite peaks versus that of main peak, the associated sources of error in accurately determining relative areas under the resonance peaks in the spectra create a challenging measurement problem. A new approach for fitting peaks in spectra with high dynamic range has been developed to address this problem, and could open the door to a new method for determining position specific 13C/12C ratios that would complement isotope ratio mass spectrometry.

Carbon stable isotope ratios from 13C satellite peaks in 1-D 1H NMR spectra

256th National Meeting (2018)

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