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 (DART™) high-resolution Orbitrap™ 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 [M–H] − , or as adduct [M + 35 Cl] − , [M + 37 Cl] − , or [M + NO 3 ] − 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

Simultaneous untargeted and targeted metabolomics profiling of underivatized primary metabolites in sulfur-deficient barley by ultra-high performance liquid chromatography-quadrupole/time-of-flight mass spectrometry

Abstract Background Metabolomics based on mass spectrometry analysis are increasingly applied in diverse scientific domains, notably agronomy and plant biology, in order to understand plants’ behaviors under different stress conditions. In fact, these stress conditions are able to disrupt many biosynthetic pathways that include mainly primary metabolites. Profiling and quantifying primary metabolites remain a challenging task because they are poorly retained in reverse phase columns, due to their high polarity and acid–base properties. The aim of this work is to develop a simultaneous untargeted/targeted profiling of amino acids, organic acids, sulfur metabolites, and other several metabolites. This method will be applied on sulfur depleted barley, in order to study this type of stress, which is difficult to detect at early stage. Also, this method aims to explore the impact of this stress on barley’s metabolome. Results Ultra-high performance liquid chromatography–high resolution mass spectrometry-based method was successfully applied to real samples allowing to discriminate, detect, and quantify primary metabolites in short-runs without any additional sampling step such as derivatization or ion pairing. The retention of polar metabolites was successfully achieved using modified C18 columns with high reproducibility (relative standard deviation below 10%). The quantification method showed a high sensitivity and robustness. Furthermore, high resolution mass spectrometry detection provided reliable quantification based on exact mass, eliminating potential interferences, and allowing the simultaneous untargeted metabolomics analysis. The untargeted data analysis was conducted using Progenesis QI software, performing alignment, peak picking, normalization and multivariate analysis. The simultaneous analysis provided cumulative information allowing to discriminate between two plant batches. Thus, discriminant biomarkers were identified and validated. Simultaneously, quantification confirmed coherently the relative abundance of these biomarkers. Conclusions A fast and innovated simultaneous untargeted/targeted method has successfully been developed and applied to sulfur deficiency on barley. This work opens interesting perspectives in both fundamental and applied research. Biomarker discovery give precious indication to understand plant behavior during a nutritional deficiency. Thus, direct or indirect measurement of these compounds allows a real time fertilization management and encounter the challenges of sustainable agriculture

Simultaneous untargeted and targeted profiling of underivatized primary metabolites on sulfur-deficient barley

International audienceMetabolomics based-mass spectrometry are increasingly applied in diverse scientific domains, notably agronomy and plant biology, to understand plants’ behaviors under biotic/abiotic stress conditions. In fact, these stress conditions are able to disrupt many biosynthetic pathways that include mainly primary metabolites. Profiling and quantifying primary metabolites remain a challenging task because they are poorly retained in reverse phase columns due to their high polarity. The aim of our method which is to simultaneously perform an untargeted/targeted metabolite profiling in order to understand the nutrient deficiency effect on plants. Two fast and accurate methods were developed to detect and quantify amino acids, organic acids, sulfur metabolites, and secondary metabolites using an UPLC coupled to a QTOF mass spectrometer. An HSS T3 column was used to analyze amino acids and sulfur containing metabolites in positive ionization mode, and a Luna R Omega PS C18 column was used for organic acids profiling in negative mode. Ionization was achieved using an electrospray ion source (ESI). Methods were successfully applied allowing to detect, quantify and discriminate primary metabolites in short-runs without any additional sampling step such as derivatization or ion pairing. On the other hand, untargeted analysis was conducted using Progenesis QI performing alignment, peak picking, normalization, metabolite identifications and multivariate analysis. The simultaneous analysis provided cumulative information allowing to discriminate between two plant batches. Thus, discriminant biomarkers were identified and validated. A fast and innovated simultaneous untargeted/targeted method has successfully been developed and applied to sulfur deficiency on Barley

Simultaneous untargeted and targeted profiling of underivatized primary metabolites on sulfur-deficient barley

International audienceMetabolomics based-mass spectrometry are increasingly applied in diverse scientific domains, notably agronomy and plant biology, to understand plants’ behaviors under biotic/abiotic stress conditions. In fact, these stress conditions are able to disrupt many biosynthetic pathways that include mainly primary metabolites. Profiling and quantifying primary metabolites remain a challenging task because they are poorly retained in reverse phase columns due to their high polarity. The aim of our method which is to simultaneously perform an untargeted/targeted metabolite profiling in order to understand the nutrient deficiency effect on plants. Two fast and accurate methods were developed to detect and quantify amino acids, organic acids, sulfur metabolites, and secondary metabolites using an UPLC coupled to a QTOF mass spectrometer. An HSS T3 column was used to analyze amino acids and sulfur containing metabolites in positive ionization mode, and a Luna R Omega PS C18 column was used for organic acids profiling in negative mode. Ionization was achieved using an electrospray ion source (ESI). Methods were successfully applied allowing to detect, quantify and discriminate primary metabolites in short-runs without any additional sampling step such as derivatization or ion pairing. On the other hand, untargeted analysis was conducted using Progenesis QI performing alignment, peak picking, normalization, metabolite identifications and multivariate analysis. The simultaneous analysis provided cumulative information allowing to discriminate between two plant batches. Thus, discriminant biomarkers were identified and validated. A fast and innovated simultaneous untargeted/targeted method has successfully been developed and applied to sulfur deficiency on Barley

Clarification of the 30 Da releases from the [M-H] − and M −• ions of trinitrotoluene by electrospray high resolution mass spectrometry

International audienceAlthough some nitroaromatic compounds can naturally occur in the environment, the vast majority of them come from anthropogenic sources. Indeed, nitroaromatic compounds such as 2,4,6-trinitrotoluene (TNT) and related-compounds are widely used as chemicals or synthetic intermediates in industrial manufacturing of explosives, dyes, pharmaceuticals, polyurethane foams and pesticides. [1] Considering the proven toxicity of nitroaromatic compounds on living organisms [2] , and their significance in the forensic sciences, much attention has been given to these compounds [3]. Thus, nitroaromatic compounds have been extensively studied by mass spectrometry (MS) coupled with different ionization sources. At first, classical vacuum ionization techniques such as Electron Ionization (EI) [4, 5] and Chemical Ionization (CI) [5-7] were widely used to examine nitroaromatic compounds. Upon the development of atmospheric pressure ionization (API) techniques, atmospheric pressure chemical ionization (APCI) [8] and electrospray ionization (ESI) [9] became established as preferred techniques to analyze nitroaromatic compounds [10]. In particular, ESI of TNT in the negative ion mode can produce competitive processes : (i) deprotonation [M-H]-and (ii) electrochemical reduction M •-. [11, 12] Afterwards, Collision-Induced-Dissociation (CID) has been extensively used for structural as well as quantitative information [13] TNT samples are commonly analyzed at low resolution by tandem mass spectrometry. Under CID conditions, these negatively charged molecular species dissociate by competitive losses of either OH • (implicating the "ortho effect", Scheme 1), or by loss of NO • (after NO 2 /ONO isomerization). In addition, NO 2  release was also observed. Scheme 1. Stepwise OH  release implicating the "ortho effect" promoted by the radical anion [M] •-(m/z 227) of TNT. In this study, we have used a standard solution (1 mg/mL in MeOH:ACN (1:1)) of 2,4,6-trinitrotoluene (TNT), obtained from AccuStandard Europe (Niederbipp, Switzerland). TNT was prepared by dilution at 1 µg mL-1 in H 2 O/MeOH (1:1), then infused at a flow rate of 5 µL min-1 into an LTQ-Orbitrap XL mass spectrometer (Thermo Fisher Scientific, Courtaboeuf, France) and ionized by ESI in the negative ion mode. The employed spray voltage was-2.5 kV giving mainly the deprotonated molecule [M-H]-at m/z 226 and th

Vacuum Ultraviolet Photoionization Study of Gas Phase Vitamins A and B1 Using Aerosol Thermodesorption and Synchrotron Radiation

International audienceGas-phase studies of biomolecules are often difficult to initiate because of the thermolability of these systems. Such studies are nevertheless important to determine fundamental intrinsic properties of the molecules. Here we present the valence shell photoionization of gas-phase vitamins A and B1 close to their ionization threshold. The study was performed by means of an aerosol thermodesorption source coupled to an electron/ion coincidence spectrometer and synchrotron radiation (SOLEIL facility, France). Ion yield curves were recorded for both molecules over a few electronvolt energy range and the threshold photoelectron spectrum was also obtained for vitamin A. Some fundamental properties were extracted for both ions such as adiabatic and the three first vertical ionization energies of retinol (IEad = 6.8 ± 0.2 eV and IEvert = 7.4, 8.3, and 9.2 eV) and dissociation appearance energies for the main fragment ions of vitamin B1. Analysis of the data was supported by ab initio calculations which show a very good agreement with the experimental observations

Transcriptomic profiles highlight the role of ABA signalling in the regulation of sweet cherry flower bud dormancy

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