1. Accurate quantitative [sup.13]C NMR spectroscopy: repeatability over time of site-specific [sup.13]C isotope ratio determination
- Author
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Caytan, Elsa, Botosoa, Eliot P., Silvestre, Virginie, Robins, Richard J., Akoka, Serge, and Remaud, Gerald S.
- Subjects
Tracers (Biology) -- Properties ,Nuclear magnetic resonance spectroscopy -- Methods ,Isotopes -- Measurement ,Chemistry - Abstract
The stability over time (repeatability) for the determination of site-specific [sup.13]C/[sup.12]C ratios at natural abundance by quantitative [sup.13]C NMR spectroscopy has been tested on three probes: enriched bilabeled [1,2-.sup.13][C.sub.2]]ethanol; ethanol at natural abundance; and vanillin at natural abundance. It is shown in all three cases that the standard deviation for a series of measurements taken every 2-3 months over periods between 9 and 13 months is equal to or smaller than the standard deviation calculated from 5-10 replicate measurements made on a single sample. The precision which can be achieved using the present analytical [sup.13]C NMR protocol is higher than the prerequisite value of 1-2 [per percent] for the determination of site-specific [sup.13]C/[sup.12]C ratios at natural abundance ([sup.13]C-SNIF-NMR). Hence, this technique permits the discrimination of very small variations in [sup.13]C/[sup.12]C ratios between carbon positions, as found in biogenic natural products. This observed stability over time in [sup.13]C NMR spectroscopy indicates that further improvements in precision will depend primarily on improved signal-to-noise ratio.
- Published
- 2007