NMR And Isotopic Fingerprinting For Food Characterisation

Numerous analytical methods have been developed during the past decades and have proven to be extremely efficient, for instance, in the case of single, high purity compounds for the measurements of concentration and/or structure elucidation. However, real-world applications often require the characterization of complex mixtures containing tens to thousands of compounds, such as biofluids, food matrices, industrial products, etc. The complete characterisation of such mixtures would be tedious, not to say impossible in the case of mixtures containing hundreds of compounds, and certainly unfeasible for monitoring purposes. In fact, one can concentrate on one or a few molecules which entail the non-negligible issue of the choice of the molecules of interest, and therefore require an a priori knowledge. Nevertheless this approach usually requires molecular separation and purification, which is time, money and human resource consuming. In contrast the Nuclear Magnetic Resonance (NMR) fingerprinting aims at establishing a holistic approach: the mixture is submitted to the NMR experiment as a whole. A simple quantification of the major compounds, which are characterised by one or several signals in the NMR spectrum, can be performed. This type of analysis is particularly attractive for several reasons: it is non-destructive, non selective and cost effective; requires little or no sample pre-treatment; uses small amounts of organic solvents or reagents; and typically takes only a few minutes per sample. The spectra of complex mixtures show hundreds of signals, coming from numerous molecules. This and the overlap of signal make it difficult to extract information, either visually or by simple processing of the data. The most effective way to analyse these holistic profiles is by using chemometric tools which enable the visualisation of the data in a reduced dimension and the classification of the samples into established classes based on inherent patterns in a set of spectral measurements. Moreover, these techniques also allow to trace the NMR spectral variables responsible of this classification, and thus, identify molecular markers of interest. Isotopic measurements such as Isotopic Ratio Mass Spectroscopy (IRMS) or Site-specific Natural Isotopic Fractionation (SNIF-NMR) provide few variables, but these contain unique information on geographical origin and metabolic or production pathways. Thus, isotopic measurements provide complementary data to NMR fingerprinting.JRC.I.5-Physical and chemical exposure

Etude des phénomènes physico-chimiques associés à la cavitation acoustique

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Interactions between Medicinal Plant Extracts and Conventional Drugs: a 19F NMR Study of Binding to Human Serum Albumin

info:eu-repo/semantics/publishe

About the Janus Double-horn Sonicator and its Use in Quantitative Homogenous Sonochemitry

info:eu-repo/semantics/publishe

Stereochemical studies by molecular palpation

The conformational equilibrium of cyclohexanol was investigated by 129X NMR spectroscopy. While the classical NMR approach focuses on a carbon or proton atom belonging to the molecule under investigation, in our 129Xe NMR methodology we use the xenon atom as an external spy. Xenon is able to monitor the interconversion between the: axial and the equatorial isomers of cyclohexanol. The conformational equilibrium constant was estimated and is in excellent agreement with the values obtained by 1H and 13C NMR. ©2004 John Wiley & Sons, Ltd.SCOPUS: cp.jFLWINinfo:eu-repo/semantics/publishe

FISCALIS Project Group - Analysis and Characterisation of Alcoholic Products (ACAP)

The purpose of the ACAP working group (composed of JRC, TAXUD and 11 Member States Custom Laboratories) was to provide scientific support for the resolution of the issue of divergent classifications of alcoholic beverages for excise duties, whether by providing objective criteria for classification, or providing sound scientific information for revision of legislation. In particular, there is a need for analytical methods allowing for the differentiation between "fermented" and "distilled" ("non-fermented") beverages and for the detection of ethanol addition. At present there is no commonly agreed solution of these problems which has resulted in the Customs Laboratories of the Member States developing their own particular approaches to deal with these issues. This can lead to divergent classification between Member States and consequent problems both for administrations and the trade. Two complementary pathways of investigation have been examined in this study: NMR fingerprinting and "classical analysis", both handled by multivariate data analysis. It is the findings of this study that it is likely to be extremely difficult or even impossible to create workable ¿general¿ models based on analytical methods. Unfortunately, the difficulties are the greatest precisely with those categories that are the most problematic for excise classification purposes. Even if an analytical model was eventually developed it is likely to need to be an extremely complex mechanism in order to take account of the broad range of beverages, and diverse chemical characteristics, of products that fall within the problem categories ("other fermented beverages" etc.). On the issue of 'added alcohol' the findings reinforce that is not plausible to ascertain the amounts by a scientific study of the finished product only. The case-to-case approach to classification applied by Member States remains therefore the only possible approach in the context of the current legislation.JRC.I.5-Physical and chemical exposure

Novel method for the measurement of xenon gas solubility using 129Xe NMR spectroscopy.

A novel method is presented for determining xenon partitioning between a gas phase and a liquid phase. An experimental setup which permits the simultaneous measurement of the 129Xe chemical shift in both the gas and the liquid phases, that is, under the same experimental conditions, has been designed. Xenon solubility is obtained via 129Xe chemical shift measurements in the gas phase. The method was validated against xenon solubility data from the literature; in general, the agreement is found to be within 3%. The solubility of xenon in three solvents for which data have not been previously reported (acetone, acetonitrile, and 1,1,2,2-tetrachloroethane) was determined using this novel method. 129Xe chemical shifts for dissolved xenon are also reported; it is found that xenon-xenon interactions may play a significant role in the liquid phase even at low equilibrium xenon pressures.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Measurements of Xenon Gas Solubility in Liquids by Xe-129 NMR

info:eu-repo/semantics/nonPublishe

Correlation between acoustic cavitation noise, bubble population, and sonochemistry

Quantitative studies of the correlation between sonochemical activity and acoustical noise spectra have been performed. The width of the second harmonic (fwhm2) of the acoustical signal in the frequency domain shows a sensitive dependence to the presence of small amounts (mM range) of an anionic surfactant in water. This sensitive dependence is also observed for other characteristics of the cavitation noise spectrum and in the sonochemical production of peroxides and correlates well with the sonoluminescence intensity observed by other researchers. Analysis of the experimental data shows that SDS probably modifies the coalescence phenomena.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Correlation between Acoustic Caviation Noise, Bubble Population, and Sonochemsitry

info:eu-repo/semantics/publishe