Gérard J. Martin

Deuterium labelling at the natural abundance level as studied by high field quantitative 2H NMR

Abstract It is shown that very large differences exist in the internal distribution of natural deuterium and the 2H quantitative NMR method is proposed as an efficient tool for characterizing the chemical and geographical origin of a molecule and for investigating chemical and biochemical mechanisms.

A coupled NMR and MS isotopic method for the authentication of natural vinegars

SummaryThe natural site-specific deuterium content and the overall 13C content of acetic acids, extracted from vinegars or obtained by chemical synthesis, were determined by NMR and mass spectrometries. The isotope ratios (D/H)CH3 and the ∂13C deviation of these samples were compared to those of a series of ethanols of the same natural or synthetic origins. The different groups of natural and fossil acetic acids are represented in the 2H/13C isotopic plane and the discriminant function, which enables unknown samples to be assigned to a given group, is computed. A careful analysis of the repeatability of the entire analytical procedure and a study of known mixtures of natural and synthetic acids show that as low as 5% synthetic acid in a natural vinegar can be detected in a comparative analysis. A sensitivity level of 15% may be expected on an absolute basis when no information on the origin of the precursors is available, providing that a determination of the botanical family of the natural component can be carried out beforehand.

Deuterium NMR in the Study of Site-Specific Natural Isotope Fractionation (SNIF-NMR)

The isotope content and in particular the ratio of deuterium and hydrogen atoms in a given molecular species, D/H, are not constant on Earth. On the basis of the overall molecular isotope contents accessible by mass spectrometry techniques, important information has been obtained on biochemical and physiological aspects of biosyntheses under natural conditions. The original approaches provided by the NMR study of Site-Specc Natural Isotope Fractionation of hydrogen must be seen in this context.

Complete assignments of the 1H, 13C and 15N NMR spectra of caffeine

Abstract Complete assignments of the 1 H, 13 C and 15 N NMR spectra of caffeine are given using a combination of modern instrumental techniques. A combination of proton coupled, decoupled, HETCOR and NH-COLOC spectra are employed to provide an unambiguous set of assignments.

High‐resolution 1H and 2H NMR spectroscopy of pure essential fatty acids for plants and animals

High‐resolution 1H and 2H NMR spectroscopy were used to study the most important saturated (C14:0, C16:0, C18:0), monounsaturated (C16:1n‐7, C18:1n‐7, C18:1n‐9, C20:1n‐9, C22:1n‐9) and polyunsaturated [C18:3n‐3, C20:5n‐3 (EPA), C22:6n‐3 (DHA)] fatty acids which may be found in fish lipids, in order to prepare the tools for a subsequent study of the recognition of the origin of fish oils by isotopic analysis. The interpretation of the 1H and 2H NMR spectra of the different acids is reported. Additionally, the overall D/H and the 13C/12C isotope ratios are given. The overall D/H ratio ranges from 114.0 to 137.2 ppm/V.SMOW (V.SMOW=water standard) and the 13C/12C ratio from ‐23.5 to ‐33.2‰. From the 2H NMR spectra, an investigation of the internal deuterium distribution in the saturated and mono‐ and polyunsaturated fatty acids was made. The deuterium distribution can be given for nearly all the chemical sites, except for the different double bonds, in EPA and DHA. The precision of the measurements was of the order of 0.5–4% depending on the nature of the cluster considered.

Applications of NMR to the characterization and authentication of foods and beverages

Abstract The adulteration of expensive commodities such as alcoholic beverages and flavouring materials is a costly type of economic fraud, when successful. In many cases the process of adulteration has become so sophisticated that conventional means of detecting adulteration, such as chromatography or proximate analysis, are no longer of value. In recent years, the traditional methods have been supplemented with techniques based on the analysis of carbon and hydrogen isotopes in low molecular weight molecules such as water, ethanol or flavour molecules. The most specific of these techniques uses NMR spectroscopy to determine site-specific isotope ratios.

Application of deuterium NMR and isotopic analysis to the characterization of foods and beverages

Abstract The adulteration of expensive commodities such as alcoholic beverages and flavouring materials is a costly type of economic fraud, when successful. In many cases, the process of adulteration has become so sophisticated that conventional means of detecting adulteration, such as chromatography or proximate analysis, are no longer of value. In recent years, the traditional methods have been supplemented with techniques based on the analysis of carbon and hydrogen isotopes in low molecular weight molecules such as water, ethanol or flavour molecules. The most specific of these techniques uses nuclear magnetic resonance spectroscopy to determine site-specific isotope ratios.

SITE SPECIFIC ISOTOPE FRACTIONATION OF HYDROGEN IN THE OXYDATION OF ETHANOL INTO ACETIC ACID. APPLICATION TO VINEGARS.

The origin of vinegars obtained by bacterial or chemical oxidation of ethanol resulting from the fermentation of various sugars is identified by a new method based on NMR determination of site specific deuterium/hydrogen ratio in acetic acid.

A magnetic diagnostic on Tore Supra

A magnetic diagnostic has been installed in Tore Supra during the year 2000. It has been designed to be compatible with the configuration Composants Internes Et Limiteur (CIEL) requirements. It consists of a set of 424 dedicated magnetic sensors, pickup coils, and flux loops. The entire system is placed in the tokamak vacuum vessel at low pressure, high temperature, and is exposed to plasma radiation. The magnetic field is determined by attaching an analog integrator to each sensor. These electronic cards were developed for long pulse operation up to 1000 s. Finally the data are acquired by a system using the VME standard. The diagnostic has been successfully operated since the restart of Tore Supra with the CIEL configuration in September 2001. It has demonstrated the capability to control the plasma during discharges of several hundreds seconds and it participates to the physics program of the CIEL Project. The technology employed for the diagnostic achievement is robust, safe, and it can be extrapolate...

A relation between the site-specific natural deuterium contents in α-pinenes and their optical activity

Abstract Correlations are observed between the optical rotation of α-pinenes and site- specific isotope ratios, (D/H) i , determined by natural abundance deuterium NMR (SNIF-NMR). The optical purity can therefore be estimated by NMR without the need for spectral separation of the enantiomers.