Dilution isotopique

La technique d'analyse par dilution isotopique est une méthode quantitative de dosage d'éléments ou d'espèces dans un échantillon. Elle est applicable à tout élément ayant au moins deux isotopes, et utilisée lors d'analyses par spectrométrie de masse. Elle consiste, sous sa forme la plus simple, à ajouter à l'échantillon à analyser une quantité bien connue d'élément enrichi en l'isotope le plus rare de l'échantillon. Ce mélange « dilue » l'isotope du standard enrichi qui a été ajouté, d'où le nom de la méthode. La dilution isotopique est classée comme une méthode à étalon interne, car le standard (la forme enrichie de l'élément à analyser) est ajouté directement à l'échantillon. De plus, contrairement aux méthodes analytiques traditionnelles qui reposent sur l'intensité du signal, la dilution isotopique s'appuie sur la mesure du rapport des signaux. En raison de ces deux avantages, la méthode de la dilution isotopique est considérée comme l'une des plus fiables et de plus haut stand

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (19)

Publications associées

Chargement

Personnes associées

Chargement

Unités associées

Chargement

Concepts associés (5)

Concepts associés

Chargement

Cours associés (2)

Cours associés

Chargement

Séances de cours associées (4)

Afficher plus

Séances de cours associées

Chargement

Validation of a nanoliquid chromatography-tandem mass spectrometry method for the identification and the accurate quantification by isotopic dilution of glutathionylated and cysteinylated precursors of 3-mercaptohexan-1-ol and 4-mercapto-4-methylpentan-2-one in white grape juices

Marc Moniatte, Jérôme Vialaret

A rapid nanoLc-MS/MS method was developed and validated for the simultaneous determination of glutathionylated and cysteinylated precursors of 3-mercapto-hexan-1-ol (3MH) and 4-methyl-4-mercaptopentan-2-one in grape juice using stable isotope dilution assay (SIDA). The analytes were extracted from must using a cation exchange resin and purified on C18 cartridges. They were chromatographically separated on a reverse phase column and finally analyzed by tandem mass spectrometry in selected reaction monitoring mode (SRM) using deuterated analogues as standards except for glutathionylated Conjugate of 4MMP which was analyzed by external calibration. The method was validated according to the International Conference on Harmonization recommendations by determining linearity, accuracy, precision, recovery, matrix effect, repeatability, intermediate reproducibility, LODs and LOQs.

2010

Chargement

Resolving the charging paradox of neat oil droplets in water

Sergey Kulik

The thesis covers the series of questions regarding the molecular structure and charge of oil nanodroplets in water. This work proposes a mechanism responsible for the stabilization of oil nanodroplets in water, which does not involve OH- adsorption. First, it describes a numerical model for absorptive processes in sum frequency scattering (SFS) experiments on nanoobjects in absorptive media. The developed approach made it possible to analyze the O-D stretch region of SFS spectra for oil droplets in D2O. With this analytical tool, the isotopic dilution of water revealed the uncoupled O-D stretch spectrum with characteristics of a stronger hydrogen bonding network compared to the bulk. Additionally, these SFS experiments revealed a broad distribution of non-hydrogen bonded modes that were red shifted and broadened compared to similar species found previously at the air/water interface. Furthermore, a polarimetric analysis of SFS spectra demonstrated that charge transfer at the oil/water interface may be responsible for stabilization of bare oil droplets in water. Finally, complimentary second harmonic scattering measurements provided further evidence that OH- adsorption can not be responsible for negative charge at the droplet's surface and an alternative mechanism was proposed, which involved charge transfer and the high conductivity of OH- ions.

EPFL2022

Chargement

Contribution à l'optimisation des entraînements électriques

Cédric Paroz

The choice of the drive composition is an obligatory stage in designing a product including electric drives. The large variety of the elements composing the electric drive (electronics, driving and kinematic chain) leads to a quasi-unlimited number of possible alternatives. Models and programs make it possible for the engineer to calculate independently the elements of a given composition, but the choice of the composition often remains subjective. We make the assumption that it is possible to automate the choice of an optimal composition. To check this assumption, the criteria, defining this optimum, are expressed and then are expressed in the form of an equation as a function of variable parameters. Finally it is checked that a set of parameters corresponding to the required optimum can be found in an automatic way. To successfully go through of these steps required the understanding of very diverse subjects, in particular: the use of an electric model, the symbolic system evaluation of the smallest root of a polynomial, the important influence of the trajectory and determination of dynainic rigidity. One of the key element resides in the formulation of the characteristics of al1 the elements in terms of admissible torque.

EPFL2003

Chargement

Atome

redresse=1.25|vignette|Représentation d'un atome d' avec, apparaissant rosé au centre, le noyau atomique et, en dégradé de gris tout autour, le nuage électronique. Le noyau d', agrandi à droite, est f

Spectrométrie de masse

thumb|right|Spectromètre de masse La spectrométrie de masse est une technique physique d'analyse permettant de détecter et d'identifier des molécules d’intérêt par mesure de leur masse, et de caracté

Isotope

thumb|upright=1.2|Quelques isotopes de l'oxygène, de l'azote et du carbone. On appelle isotopes (d'un certain élément chimique) les nucléides partageant le même nombre de protons (caractéristique de

CH-419: Protein mass spectrometry and proteomics

In systems biology, proteomics represents an essential pillar. The understanding of protein function and regulation provides key information to decipher the complexity of living systems. Proteomic technology now enables deep quantitative proteome mapping via mass spectrometry.

CH-160(en): Advanced general chemistry (english)

This course aims to teach essential notions of the structure of matter, chemical equilibria and reactivity. Classes and exercises provide the means to analyze and solve, by reasoning and calculation, novel problems of geeneral chemistry.