Chapter 5 - Natural Abundance 2H-NMR Spectroscopy. Application to Food Analysis

Abstract

This chapter presents an introductory survey of the fundamentals and the use of 2H-NMR at natural abundance. The basic principles of nuclear magnetic resonance (NMR) spectroscopy with specific considerations about the observation of deuterium at natural abundance from both theoretical and practical aspects are also discussed. The isotope ratio mass spectrometry (IRMS) and deuterium nuclear magnetic resonance (2H-NMR) techniques are mainly used for the measurement of the stable isotope content. 2H-NMR is demonstrated to be very useful for site-specific characterization of organic molecules especially for the intramolecular distribution of deuterium. The use of relatively large sample sizes, 2H-NMR provides a fingerprint of the deuterium content that can be correlated with its natural or synthetic or geographic origin due to its lack of sensitivity. NMR spectroscopy is based on the properties of some nuclei that have non-zero spin angular momentum. The total deuterium content of natural compounds depends on several physical, chemical, or physiological effects leading to isotope fractionation. 2H-NMR is proved to be reliable in the implementation of legislation regarding food products throughout the food industry such as ethanol, raspberry ketone, phenylacetic acid or benzoic acid, and various other molecules. Hence, the determination of stable isotope ratios is of great interest in various fields of scientific research such as geochemistry, hydrology, medicine, biochemistry and food science.