7 research outputs found
Combined use of direct analysis in real-time/Orbitrap mass spectrometry and micro-Raman spectroscopy for the comprehensive characterization of real explosive samples
International audienceDirect Analysis in Real Time (DARTâą) high-resolution Orbitrapâą mass spectrometry (HRMS) in combination with Raman microscopy was used for the detailed molecular level characterization of explosives including not only the charge but also the complex matrix of binders, plasticizers, polymers, and other possible organic additives. A total of 15 defused military weapons including grenades, mines, rockets, submunitions, and mortars were examined. Swabs and wipes were used to collect trace (residual) amounts of explosives and their organic constituents from the defused military weapons and micrometer-size explosive particles were transferred using a vacuum suction-impact collection device (vacuum impactor) from wipe and swap samples to an impaction plate made of carbon. The particles deposited on the carbon plate were then characterized using micro-Raman spectroscopy followed by DART-HRMS providing fingerprint signatures of orthogonal nature. The optical microscope of the micro-Raman spectrometer was first used to localize and characterize the explosive charge on the impaction plate which was then targeted for identification by DART-HRMS analysis in both the negative and positive modes. Raman spectra of the explosives TNT, RDX and PETN were acquired from micrometer size particles and characterized by the presence of their characteristic Raman bands obtained directly at the surface of the impaction plate nondestructively without further sample preparation. Negative mode DART-HRMS confirmed the types of charges contained in the weapons (mainly TNT, RDX, HMX, and PETN; either as individual components or as mixtures). These energetic compounds were mainly detected as deprotonated species [MâH] â , or as adduct [M + 35 Cl] â , [M + 37 Cl] â , or [M + NO 3 ] â anions. Chloride adducts were promoted in the heated DART reagent gas by adding chloro-form vapors to the helium stream using an Bin-house^ delivery method. When the polarity was switched to positive mode, DART-HRMS revealed a very complex distribution of poly-meric binders (mainly polyethylene glycols and polypropylene glycols), plasticizers (e.g., dioctyl sebacate, tributyl phosphate), as well as wax-like compounds whose structural features could not be precisely assigned. In positive mode, compounds were identified either as protonated molecules or am-monium adduct species. These results clearly demonstrate the complementarity of micro-Raman microscopy combined with DART-MS. The former technique provides structural information on the type of explosives present at the surface of the sample, whereas the latter provides not only a confirmation of the nature of the explosive charge but also useful additional information regarding the nature of the complex organic matrix of binders, plasticizers, polymers, oils, and potentially other organic additives and contaminants present in the sample. Combining these two techniques provides a powerful tool for the screening, comprehensive characterization, and differentiation of particulate explosive samples for forensic sciences and homeland security applications
The molecular composition of humic substances extracted from green composts and their potential for soil remediation
Characterization of Fluorinated Polymers by Atmospheric-Solid-Analysis-Probe High-Resolution Mass Spectrometry (ASAP/HRMS) Combined with Kendrick-Mass-Defect Analysis
Fluorinated
polymers are a diverse and important class of polymers
with unique applications. However, characterization of fluorinated
polymers by conventional mass spectrometric methods is challenging
because (i) their high fluorine contents make them insoluble or only
sparingly soluble in most common solvents and (ii) commonly used matrices
employed for MALDI do not desorb or ionize them efficiently. In this
work, atmospheric-solid-analysis-probe (ASAP) high-resolution orbitrap
mass spectrometry (HRMS) was used as a new tool for the molecular
characterization of various fluorinated polymers, including polyvinylidene
fluoride (PVDF) and fluorinated copolymers containing PVDF and chlorotrifluoroethylene
(KEL-F 800) or PVDF and hexafluoropropylene (Viton A and Tecnoflon).
The major peaks of the observed distributions were assigned compositions,
but the high number of species required the use of an alternative
method to treat such complex data. Kendrick-mass defects (KMD) were
calculated on the basis of the âcommon-to-allâ vinylidene
difluoride repeating unit. By plotting the KMD as a function of the
nominal Kendrick masses (NKM), specific patterns based on homologous
series emerged. Kendrick maps were therefore drawn to simplify the
mass spectra and provide confident peak assignments through homologous-series
recognition. A specific fingerprint for each polymer has been identified,
and the ability to discern the four species present in a blend through
KMD analysis was demonstrated
A Systematic Tandem Mass Spectrometric Study of Anion Attachment for Improved Detection and Acidity Evaluation of Nitrogen-Rich Energetic Compounds
Couplage de sources dâionisation ambiante Ă la spectromĂ©trie de masse : comparaison entre les sources DESI et DART et applications Ă lâanalyse de traces dâexplosifs
National audienceCet article prĂ©sente les principes de fonctionnement et le montage expĂ©rimental de deux sources dâionisation ambiante commerciales pour la dĂ©tection par spectromĂ©trie de masse haute rĂ©solution de composĂ©s organiques Ă lâĂ©tat de traces~: la dĂ©sorption et ionisation par Ă©lectronĂ©bulisation (DESI) et la technique dâanalyse directe en temps rĂ©el (DART).Il sâagit de mĂ©thodes dâanalyse directes, rapides, en temps rĂ©el, ne nĂ©cessitant pas, ou trĂšs peu, de traitement prĂ©alable de lâĂ©chantillon, ni de couplage avec des techniques de sĂ©parations molĂ©culaires telles que des sĂ©parations chromatographiques. Les applications prĂ©sentĂ©es illustrent clairement la capacitĂ© de ces mĂ©thodes Ă dĂ©tecter des molĂ©cules organiques prĂ©sentes sur des surfaces, voire de reconstituer la distribution des espĂšces molĂ©culaires Ă la surface de lâĂ©chantillon par imagerie.Le couplage de ces sources dâionisation ambiante et de la spectromĂ©trie de masse haute rĂ©solution permet dâobtenir des mĂ©thodes de mesures rapides (analyse en quelques minutes), fiables (justesse en masse exacte) et sensibles (quelques nanogrammes, voire picogrammes de matiĂšre)
Identification of Postblast Residues by DART-High Resolution Mass Spectrometry Combined with Multivariate Statistical Analysis of the Kendrick Mass Defect
Fingerprinting the elemental composition and chemodiversity of vegetation leachates: consequences for dissolved organic matter dynamics in Arctic environments
Dissolved organic matter is a key compartment for biogeochemical cycles in the Arctic and Subarctic terrestrial environments. With changing vegetation ecosystems, the chemical composition of organic matter is expected to shift and thus, the most labile part of it, namely the extractable fraction. To this date, few studies have focused on the fingerprinting of DOM fraction from different primary sources, and even less on its potential repercussions on the environment. In this study, we jointly characterized the chemical composition of bulk and water-extractable organic matter (WEOM) from different vegetation species typical of Subarctic ecosystems. Through a multi-analyses approach, including elementary analysis, solid state 13C nuclear magnetic resonance, UV and 3D fluorescence spectroscopy, and high-resolution mass spectrometry, our results highlighted that the quantity and composition of produced WEOM significantly differed between vegetation sources and specifically between plant functional types (PFT, e.g., lichens, graminoids, and trees and shrubs). The relevance of optical indices was questioned, and the use of several of them was discarded for unprocessed WEOM study. However, the DOM proxies (optical indices, molecular composition, and stoichiometry) enabled to conclude that the lichen WEOM was likely less degradable than vascular plants WEOM, and among the latter group, graminoids produced more degradable WEOM than trees and shrubs. This work reported specific organic fingerprints for the different PFT. Consequently, the ongoing changes of vegetation in Arctic and Subarctic regions may greatly affect the composition of DOM that enters the soil and the hydrosystems, as well as the biogeochemical processes it is involved in