Chromatographie en phase liquide-spectrométrie de masse

Résumé

La chromatographie en phase liquide couplée à la spectrométrie de masse (en anglais Liquid chromatography-mass spectrometry ou LC-MS) est une méthode d'analyse qui combine les performances de la chromatographie en phase liquide et de la spectrométrie de masse afin d'identifier et/ou de quantifier précisément de nombreuses substances. Une unité LC-MS est composée de deux blocs principaux : un chromatographe en phase liquide et un spectromètre de masse. Références liens externes Catégorie:Méthode de la biochimie Catégorie:Chromatographie Catégorie:Spectrométrie de masse Catégorie:Technique couplée

Source officielle

https://fr.wikipedia.org/wiki/Chromatographie_en_phase_liquide-spectrom%C3%A9trie_de_masse

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 (81)

Publications associées

Chargement

Personnes associées (8)

Personnes associées

Chargement

Unités associées (3)

Unités associées

Chargement

Concepts associés (21)

Concepts associés

Chargement

Cours associés (12)

Cours associés

Chargement

Séances de cours associées (37)

Séances de cours associées

Chargement

Characteristics of isobaric tagging-based peptide quantification by high resolution tandem-in-time mass spectrometry

Sébastien Falk

2009

Chargement

, ,

A paradigm shift is underway in the field of quantitative liquid chromatography-mass spectrometry (LC-MS) analysis thanks to the arrival of recent high-resolution mass spectrometers (HRMS). The capability of HRMS to perform sensitive and reliable quantifications of a large variety of analytes in HR-full scan mode is showing that it is now realistic to perform quantitative and qualitative analysis with the same instrument. Moreover, HR-full scan acquisition offers a global view of sample extracts and allows retrospective investigations as virtually all ionized compounds are detected with a high sensitivity. In time, the versatility of HRMS together with the increasing need for relative quantification of hundreds of endogenous metabolites should promote a shift from triple-quadrupole MS to HRMS. However, a current "pitfall" in quantitative LC-HRMS analysis is the lack of HRMS-specific guidance for validated quantitative analyses. Indeed, false positive and false negative HRMS detections are rare, albeit possible, if inadequate parameters are used. Here, we investigated two key parameters for the validation of LC-HRMS quantitative analyses: the mass accuracy (MA) and the mass-extraction-window (MEW) that is used to construct the extracted-ion-chromatograms. We propose MA-parameters, graphs, and equations to calculate rational MEW width for the validation of quantitative LC-HRMS methods. MA measurements were performed on four different LC-HRMS platforms. Experimentally determined MEW values ranged between 5.6 and 16.5 ppm and depended on the HRMS platform, its working environment, the calibration procedure, and the analyte considered. The proposed procedure provides a fit-for-purpose MEW determination and prevents false detections.

Amer Chemical Soc2016

Chargement

Infrared photofragment spectroscopy of charged amino acid water clusters in the gas phase

Anthi Kamariotou

We present in this work a new technique, which combines laser photofragmentation spectroscopy with tandem mass spectrometry, for structural investigations of biomolecular ions in the gas phase. A novel apparatus was designed and built for the implementation of these studies. In this instrument closed shell ions are produced in the gas phase by electrospray ionization and stored in a hexapole ion trap prior to mass selection of a parent beam in a first quadrupole and then irradiation in an octupole ion guide using laser light. Mass analysis of the photofragmentaion products in a final stage quadrupole as a function of the wavelength generates an action spectrum. We applied this new technique to follow the microsolvation of charged amino acids in the gas phase. In these studies, the nanoelectrospray ionization source generates a distribution of water clusters of charged amino acids at various hydration levels. A particular size of cluster is selected and irradiated by infrared laser pulses resulting in the dissociation of one water molecule. Detection of the photofragmentation of this weak non-covalent bond allows us to generate the vibrational action spectrum of this particular cluster. We use a two-stage difference frequency mixing setup to produce laser light in the 2900–3800 cm-1, allowing us to probe the light-atom stretching region. IR photofragmentation spectra have been obtained for the hydrates of protonated and lithiated valine and those of protonated tryptophan. By probing the region of free and hydrogen-bonded N-H and O-H stretch vibrations and with the help of density functional theory calculations at the B3LYP/6-31++G** level, we relate spectral changes to the structure of clusters. In the study of lithiated valine water clusters, we addressed the question of zwitterion formation upon the combined effect of water and an external ion. Our data indicate the presence of the non-zwitterionic form of valine upon addition of up to four water molecules. In all of the species studied here, the hydration process is driven by solvation of the charge, and upon completion of a first shell around it, water preferentially forms a second solvation shell with no strong competition from other hydration sites on the amino acid backbone. Strikingly, similar water network structures have been observed at the highest hydration level of completely different species, probably indicating the existence of stable ordered water structures. We obtained evidence for a structrual change of the valine backbone in lithiated valine upon addition of the third water molecule, while no conformational change has been identified in the clusters of the protonated species. We have thus been able to answer questions related to the conformational preferences of the amino acid and the structuring of the water network.

EPFL2006

Chargement

Infrared photofragment spectroscopy of charged amino acid water clusters in the gas phase

Anthi Kamariotou

EPFL2006