Stable Isotope Analysis of Food and Beverages by Nuclear Magnetic Resonance

TLDR: In this article, the authors used isotopic dilution to estimate the linearity of the NMR response and therefore the consistency of possible systematic errors, and then compared the accuracy of NMR determinations with those of the balance.

Abstract: Publisher Summary Nuclear magnetic resonance is the only analytical method that is able to detect simultaneously the different isotopomers of a given chemical species, provided the isotope under consideration has a magnetic moment and the chemical shift discrimination is large enough. In 1981, it was shown that deuterium atoms at natural abundance exhibit large deviations with respect to a statistical distribution among the different sites of a molecule. In order to estimate the accuracy of the NMR determinations an isotopic dilution technique can be used. The NMR performances are then compared to those of the balance and it is possible to appraise the linearity of the NMR response and therefore the consistency of possible systematic errors. The ability of the method to detect adulteration by exogenous sugars is improved when environmental conditions are taken into account. More than 800 carbohydrate samples of starches or sugars extracted from cereals, tubers and leguminosae (maize, sorghum, rice, wheat, barley, potato, bean), from fruits (pineapple, citrus, apple, soft fruits), and from sugar plants (beet, cane) were studied in order to constitute a confident database.