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Laser desorption mass spectrometry was employed to study rubrene using three different sample preparation methods. Pressed-pellet and films drop-cast from solution were investigated with a laser-desorption time-of-flight spectrometer. Jet-cooled rubrene cations were produced in a supersonic molecular beam by laser desorption from a film-coated metal rod and detected with time-of-flight mass spectrometry. The films for this process were produced by vacuum sublimation of powder samples. The mass spectra from each of these samples contained the parent molecular ion and fragments resulting from phenyl ring elimination - a pattern similar to that produced by electron impact ionization. The amount of fragmentation varied with sample preparation and desorption laser wavelength. The rubrene cation was mass selected and studied with UV laser photodissociation at 355 nm. The resulting fragmentation mass spectrum indicated the loss of one or two phenyl groups, but no more than this. Computational studies of the ion energetics were used to investigate the stable fragment ion structures and understand the energetics of the dissociation process. [Display omitted] • Laser desorption mass spectrometry studied for rubrene at 532 and 355 nm. • Strong wavelength dependence for LD-ToF. • Photodissociation of mass-selected rubrene cation at 355 nm. • Computational studies of fragmentation energetics. • Elimination of biphenyl as dominant photochemical path. [ABSTRACT FROM AUTHOR]

The antiProton Unstable Matter Annihilation experiment (PUMA) at CERN aims at investigating the nucleon composition in the matter density tail of radioactive as well as stable isotopes by use of low-energy antiproton-nucleon annihilation processes. For this purpose, antiprotons provided by the Extra Low ENergy Antiproton (ELENA) facility will be trapped together with the ions of interest. While exotic ions will be obtained by the Isotope mass Separator On-Line DEvice (ISOLDE), stable ions will be delivered from an offline ion source setup designed for this purpose. This allows the proposed technique to be applied to a variety of stable nuclei and for reference measurements. For beam purification, the ion source setup includes a multi-reflection time-of-flight mass spectrometer (MR-ToF MS). Supported by SIMION® simulations, an earlier MR-ToF MS design has been modified to meet the requirements of PUMA. During commissioning of the new MR-ToF device with Ar+ ions, mass resolving powers in excess of 50,000 have been obtained after 150 revolutions, limited by the chopping of the continuous beam from an electron impact ionisation source. • Versatile ion source setup delivers isotopically pure and cooled ion bunches. • Development of a new MR-ToF MS for high-precision ion beam purification. • SIMION simulations increase the MR-ToF MS performance. • Modular electrode design enables flexible geometry changes. • In-trap deflector allows mass-selective transversal ion ejection. [ABSTRACT FROM AUTHOR]

The ubiquity and potential toxicity of phthalates make their exposure on humans a matter of great concern. Measuring the targeted phthalate metabolites using liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a commonly used approach for human biomonitoring of phthalates. However, the targeted LC-MS/MS methods have been unable to meet the desire to comprehensively and rapidly screen and identify for as many known and potentially unknown phthalate metabolites in human samples. Instead, non-targeted screening methods, allowing the rapid detection and identification of unknown compounds in a wide variety of environmental and human samples are complementary to the targeted methods. In this study, 23 phthalate metabolites were analyzed using liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) for development of a non-targeted screening method. The fragmentation patterns of the 23 phthalate metabolites were investigated using collision-induced dissociation experiments at 10, 20, and 40 eV. And three common specific product ions at m/z 121.0297, m/z 147.0088, and m/z 165.0193 corresponding to C 7 H 5 O 2 -, C 8 H 3 O 3 -, and C 8 H 5 O 4 -, respectively were observed in their mass spectra. Based on the three common product ions, a new strategy was proposed for non-targeted screening of the new phthalate metabolites as exposure biomarkers for human biomonitoring. It can greatly reduce the time spent on data processing for potential precursor ions. Additionally, the correlation of the retention time and logKow of the phthalate metabolites was explored, which provides a useful tool to reduce the number of identified candidates in the non-targeted screening. Image 1 • 23 native phthalate metabolites standards were analyzed by HPLC-QTOF-MS/MS. • A strategy for identification of phthalate metabolites has been proposed. • A simpler retention prediction model was plotted. • The strategy is useful for non-targeted screening of new biomarkers of phthalates exposure for human biomonitoring. [ABSTRACT FROM AUTHOR]

High-resolution mass spectrometry using the time of flight (TOF) technique with a reflectron with multiphoton absorption was used to analyze the fragmentation pattern of nitromethane in a collision-free system. We used a radiation source with nanosecond laser pulses of 532 nm, 355 nm, and 266 nm wavelengths and a supersonic jet of nitromethane to produce positive fragment ions. The density power (irradiation) range was from 109 to 1010 W/cm2. The identification of 20 ions at a wavelength of 532 nm was obtained, whereas at 266 nm, more than 60 fragment ions were identified, as was the parent ion and many clusters. We associate these ionic fragments as a function of the intensity, energy, and pulse duration of the radiation source. The observation of radicals such as CH 1,2,3 , C 2 H 1,2,3 , C 3 H 1,2,3 , and CH 3 O, CHNO, higher mass molecules, and clusters is presented. The absence of the parent ion at 532 nm and 355 nm wavelengths demonstrates that the ladder switching mechanism elucidates the dissociation-ionization (DI) pathways of nitromethane. At 266 nm, the presence of the parent ion and the clusters are an indication of the functioning of the other model of fragmentation (ID). Due to the experimental characteristics, the numerous fragments seem to be a result of the interactions of the intensity of the electromagnetic radiation over nitromethane in the gas phase and their clusters. • The experimental settings allow the cluster formation. • At 532 nm the products of the major and minor dissociation paths was identified. • At UV interactions the clusters originate the radicals CH 1,2,3 , C 2 H 1,2,3 , C 3 H 1,2,3. [ABSTRACT FROM AUTHOR]

This work applies the technique of mapping ion detection using a reflectron mass spectrometer against flight-time and reflection voltage to elucidate the complex metastable fragmentation pattern of the biomolecular ion 3-aminophenol+ (3-AP+, C 6 H 7 NO+). Multi-photon ionization experiments revealed the excited ion's fragmentation routes for the first time and comparisons with calculated flight-times enabled 18 different μs-timescale dissociations to be assigned. These included the rare observation of a double hydrogen loss channel from a fragment ion. DFT calculations provided further insights into the most prominent apparent fragmentation sequence: 3-AP+ (m / z 109) → HCO + C 5 H 6 N+ (m / z 80) → CNH + C 4 H 5 + (m / z 53) → C 2 H 2 + C 2 H 3 + (m / z 27). Image 1 • 2D mapping reveals an exceptionally rich metastable dissociation pattern of 3AP+. • Double hydrogen loss has been detected from a fragment ion – a rare observation. • Ab initio calculations elucidated the strongest apparent fragmentation sequence. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon dots (N-CDs) were synthesized by microwave-assisted pyrolysis of citric acid and urea for use as an alternative matrix for the detection of small molecules using matrix-assisted laser desorption/ionization spectrometry (MALDI-MS). The synthesis of N-CDs is much simpler than that of other nitrogen-doped carbon matrices used in MALDI-MS, which has been a major limitation to its application. The synthesized N-CDs were characterized using various analytical methods. The high optical absorbance and good dispersibility of the obtained N-CDs showed them to be an ideal matrix for detecting analytes such as glucose, sucrose, amino acids, nilotinib, and polyethylene glycols. The application of N-CDs as a MALDI matrix improved the signal response of small molecules due to the specific aromatic structure and the doping of nitrogen atoms. The minimum detectable amounts using an N-CDs matrix in MALDI-MS were found to be in the range of 1 nmol–1 pmol, with a lower minimum detectable amount of arginine (1 pmol) than previously reported. Image 1 • Simple synthesis of nitrogen-doped carbon dots (N-CDs) by microwave pyrolysis. • Complete characterization of N-CDs. • Novel application of N-CDs as MALDI matrix. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MALDI-TOF have become more popular for identification of dermatophytes whose identification is more complicated than that of bacteria. • Dermatophyte were identified following direct deposit/formic acid or an Ethanol/formic acid complete extraction. • Ethanol/formic acid extraction complete extraction protocol had a 100% correct identification rate. • 65% of dermatophytes were identified to species level in the Ethanol/formic acid extraction complete extraction protocol. Abstract Conventional dermatophyte diagnosis includes microscopic and macroscopic characterization of the fungi by a skilled mycologist following fungi cultivation for several weeks. In recent years, matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) has become useful for highly specific and sensitive identification of bacteria and yeasts from clinical samples. The current study aimed to test the influence of using a protein extraction protocol on dermatophyte identification by MALDI-TOF MS. We collected scrapings of affected skin from forty-six patients diagnosed with tinea. Each sample was cultured on four tubes of Sabouraud Dextrose Agar. After 21–28 days of incubation, fungi morphology was examined by an expert mycologist according to standard microscopic and macroscopic colony characteristics. Dermatophyte identification by MS was performed following 14 (Protocol I) or 21 (Protocol II) days of incubation with direct deposit and addition of formic acid or following an Ethanol/formic acid extraction – "EtOH/FA complete extraction protocol" after 14 days (Protocol III). We found that the EtOH/FA complete extraction protocol had a 100% correct identification rate. While identification to species level was obtained in 0% and 22% of the dermatophytes following Protocol I and Protocol II, respectively, the EtOH/FA complete extraction protocol resulted in 65% identification to the species level. Considering the straightforward performance of the EtOH/FA complete extraction protocol and the high accuracy, we recommend its implementation in routine diagnosis in clinical laboratories. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Water-soluble selenocompound profiles of selenised yeasts differed significantly. • Ultrafiltration proved successful for yeast extract clean-up. • Over 180 selenocompounds were detected in selenised yeast after a water extraction. • 129 of the 188 selenocompounds detected were novel selenocompounds. • Elemental composition was proposed for 14 novel selenocompounds. Abstract Liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS) was utilised for the screening of organoselenium metabolites in the water extracts of selenised yeast products. Four different commercially available yeast products and a reference Se-enriched yeast standard, (SELM-1) were analysed. Total selenium and selenomethionine concentrations were determined by ICP-MS and LC-ICP-MS, respectively. Ultrafiltration using a 3 kDa molecular weight cut-off membrane was used in the present study for sample clean-up. The water-soluble extracts were lyophilised to increase analyte concentration, resuspended in water and analysed by liquid chromatography-electrospray ionisation quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS). Selenium-containing species were confirmed using selenium's unique isotopic pattern. This approach allowed for the detection of approximately 129 previously unreported selenium metabolites across the different yeast samples. Determination of the elemental composition of 14 previously unreported selenocompounds was advanced through MS2 analysis and accurate molecular mass determination (Δ ppm<1.6 for all proposed elemental compositions). [ABSTRACT FROM AUTHOR]

The degradation of the insecticide fenamiphos was undertaken by using a homogeneous photocatalysis employing iron (III) aqua complex, [Fe(H 2 O) 5 (OH)]2+. The irradiation was studied by excitation at 365 nm and the generated primary by-products were elucidated by Liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry in the positive ion mode, that leads to the formation of the protonated forms of the studied compounds, [M + H+]. Collision-induced dissociation tandem mass spectrometry (CID-MS/MS) of the protonated molecules was carried out, and the effect of the collision energy as well as the elemental compositions of the product ions were used in order to propose the chemical structures. The primary processes were then i) hydroxylation on the aromatic ring; ii) the loss of propene from the aminoisopropyl chain and iii) the loss of the methylene at the ethoxy moiety. [Display omitted] • Homogeneous photocatalysis at 365 nm of fenamiphos using aqueous iron (III) complex. • Hydroxyl radicals are the main species involved. • Byproducts were elucidated by Collision-induced dissociation/mass spectrometry. • Hydroxylation, loss of propene and methylene are the main processes. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) and heavy metal ions significantly threaten human health. Hence, there is an urgent need to develop a faster and simpler method to detect these pollutants in water. Vacuum ultraviolet photoionization time-of-flight mass spectrometry (VUP-TOF-MS) shows an advantage in detecting these pollutants. The VUP-TOF-MS offers a wide detection range due to its ability to ionize analytes using photons and energetic photoelectrons. In this study, we report the first-ever simultaneous detection of VOCs and heavy metal ions in water using a single TOF-MS. We designed a novel combined sampling, which extracted the analytes from water into the gas phase. This was followed by photoionization by the VUP ion source with switched ionization modes. We also investigated ionization mechanisms to explain the characteristic peaks. The detection limits of these analytes ranged from 5.4 × 10−2 to 36.8 μg L−1. We monitored the river water and observed recoveries in the range of 94–118%. Thus, the proposed method provides a new possibility for the simultaneous online detection of VOCs and heavy metal ions by mass spectrometry. [Display omitted] • Simultaneous detection of VOCs and heavy metal ions in water was first achieved on a single mass spectrometry. • A novel sampling system for simultaneous extraction of VOCs and heavy metal ions from water to the gas phase was constructed. • This strategy provides new insights for the online water quality monitoring. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Experiments in mass spectrometry carried out during the 1980s led to the discovery of the fullerenes. The underlying aim behind these was to understand the formation of carbon chains identified in the interstellar medium some years earlier by radioastronomy. The stability of the discovered C 60 cage structure led immediately to speculation concerning its role in the context of the diffuse interstellar bands, a set of several hundred optical absorptions observed in the spectrum of reddened star light. The identities of the molecular carriers responsible for these have remained elusive for a century. In 2015, laboratory measurements carried out using a cryogenic ion trap led to the confirmation that C 60 + is responsible for two of the unidentified absorption bands, providing the first clue as to their origin. In this contribution we focus on the experiments that led to this identification. The consequences of this and for other molecules present in such environments is discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Powerful options by coupling two meter drift tube to two meter time-of-flight tube. • High mass resolution readily identifies an ion (e.g. charge state, oligomer size). • Mobility-selected ions are readily identified by isotope pattern. • Ion selection with high mass resolution aids in interpretation of mobility data. Abstract A new instrument combining a two meter long ion mobility drift tube fabricated of resistive glass with a high-resolution time-of-flight (TOF) mass spectrometer is presented and new features are discussed in detail. Ions are formed by electrospray ionization. An ion gate positioned at the exit of the drift tube allows analysis of mobility-selected ions. A quadrupole mass filter and a collision cell are located between the drift tube and the TOF analyzer, an arrangement which allows collision-induced dissociation experiments of mass-selected and/or mobility-selected ions. The ability of the TOF spectrometer to resolve isotopologues differing by 1 Da in mass even for multiply charged ions opens up exceptional possibilities for ion selection and mobility analysis. The unique combination of instrument attributes including gentle ion production and analysis, the first principles measurement of cross sections, and high mobility (R∼100) and mass (R>20k) resolving powers allows for the analysis of a broad range of analytes including amino acid oligomer clusters (e.g. Phe 97), peptides, and proteins. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • New metabolites of vardenafil were found and their chemical structures were elucidated. • The complete hepatic metabolism pathway of vardenafil was proposed. • Chemometric method was used for multivariate comparison of photocatalytic and HLM biological metabolic LC-ESI-HRMS profiles. • For the first time WO 3 catalyst was used for simulation of drug metabolism process. • A heterogeneous WO 3 photocatalysis was found to be a complementary method for mimicking phase I metabolism reactions. Abstract The in vitro metabolism of vardenafil, a selective phosphodiesteraze type 5 (PDE-5) inhibitor was investigated with the use of biological HLM method in comparison to TiO 2 and WO 3 assisted photocatalytic approach. The main objective of this study was to identify the transformation routes and elucidate metabolite structures. The samples were analyzed by LC-ESI-HRMS system to obtain metabolism pathways and confirm the structures of new metabolites. Deethylated vardenafil was identified as a main transformation product and additionally, nine new, not yet described, metabolites were found in HLM samples. The photocatalytic process with the use of TiO 2 and WO 3 allowed to observe five and seven transformation products respectively. The multivariate chemometric comparison of the obtained results shows WO 3 assisted photocatalysis as a more suitable approach of phase I metabolism simulation method. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • New operational mode of ion preparation trap used for multi-reflection time-of-flight mass spectrograph. • Improved method for determination of ion mass for spectral peaks outside the nominal mass bandwidth of a multi-reflection time-of-flight mass spectrograph. • Accurate relative precision of 10−7 can be obtained even without isobaric reference ion. Abstract We introduce a new concomitant referencing mode for operating a multi-reflection time-of-flight mass spectrograph (MRTOF-MS), wherein the reference and analyte ions are interleaved on a cycle by cycle basis. Using this mode, we demonstrate an improved technique for performing wide bandwidth mass measurements via MRTOF-MS. This new technique offers a simplified analysis and high accuracy. [ABSTRACT FROM AUTHOR]

A low-cost time-of-flight mass spectrometer has been developed to characterize the plasma plume resulting from pulsed laser ablation. In this paper, an ionic liquid ion source using EMI-BF 4 is used to experimentally validate the spectrometer, as well as a model of the spectrometer. The mass spectrometer is shown to experimentally measure the energy-per-charge distribution of the ion source, and match with literature. In addition, a relation between alignment error and measurement error predicted by theory is confirmed, further validating the model. Now that it has been validated, the spectrometer can confidently be used to determine the two-dimensional distribution of speed and energy-per-charge of a pulsed laser ablation plasma, or other pulsed plasma sources. [ABSTRACT FROM AUTHOR]

The simultaneous multi-element isotope ratio measurement by inductively coupled plasma time of flight mass spectrometry (ICP-TOFMS) was examined to evaluate the possibility of simultaneous multi-element determination by isotope dilution mass spectrometry (IDMS). Output from the two different ICP-TOFMS instruments (icpTOF and Optimass 9500) were examined and the figures of merit between them were determined from the analytical results of intensity ratios as isotope ratio measurements for 10 elements ( 137 Ba/ 135 Ba, 111 Cd/ 112 Cd, 63 Cu/ 65 Cu, 69 Ga/ 71 Ga, 60 Ni/ 62 Ni, 208 Pb/ 206 Pb, 107 Ag/ 109 Ag, 205 Tl/ 203 Tl, 238 U/ 235 U and 66 Zn/ 68 Zn). For the results, linear calibration curves for all elements, except for 235 U obtained by icpTOF, with coefficient of determination (r 2 ) of more than 0.999 could be obtained for both ICP-TOFMS instruments in the range of concentration from 1 ng mL −1 to 100 ng mL −1 , even though the sensitivities of elements were slightly different. However, the trends of intensity ratios of elements observed were different between two ICP-TOFMS instruments, especially for heavier elements such as Pb, Tl and U. The icpTOF provided consistent isotope ratios at the concentrations from 1 ng mL −1 to 100 ng mL −1 for most of elements examined, although Optimass 9500 did not provide consistent isotope ratios except for Ba, Ga and Ag. From these analytical results, icpTOF appears to be the better instrument for simultaneous multi-element determination by IDMS compared to Optimass 9500. Consequently, the simultaneous IDMS of Cd, Hg and Pb by icpTOF was demonstrated to examine the possibility of simultaneous multi-element IDMS by ICP-TOFMS and the consistent analytical results with respect to the certified values could be obtained. From these results, it was expected that icpTOF could be used for simultaneous multi-element IDMS to obtain accurate and precise analytical results since it provided consistent isotope ratios of elements. [ABSTRACT FROM AUTHOR]

High-precision mass measurements of Cu 63 , Zn 64 − 66 , Ga 65 , Ge 65 − 67 , As 67 , Br 78 , 81 , Rb 80 , and Sr 79 were performed utilizing a multireflection time-of-flight mass spectrograph combined with the gas-filled recoil ion separator GARIS-II. In the case of Ga 65 , a mass uncertainty of 2.1 keV, corresponding to a relative precision of δm / m = 3.5 × 10 −8 , was obtained and the mass value is in excellent agreement with the 2016 Atomic Mass Evaluation. For Ge 67 and Br 81 , where masses were previously deduced through indirect measurements, discrepancies with literature values were found. The feasibility of using this device for mass measurements of more neutron-deficient nuclei, which have significant impact on the rp -process pathway, is discussed. [ABSTRACT FROM AUTHOR]

An ion trap/time-of-flight mass spectrometer equipped with a metastable atom bombardment (MAB) ionization source was constructed in order to observe ion-molecule reactions controlled by the internal energy of ions. In the MAB source, the internal energy of the generated ions was controlled by using different rare gases. Moreover, the constructed device was used to analyze ion-molecule reactions of the p -xylene cation and its dissociation ions with p -xylene. It was found that the reaction afforded a single product without any structural isomers, which could then be easily analyzed. An abundant amount of [M] + ( m / z 106, C 8 H 10 + ) and trace levels of dissociation products were observed in the Kr MAB ionization, while in the Ar MAB ionization, [M−CH 3 ] + , [M−H] + ( m / z 105, C 8 H 9 + ), and [M+CH] + ( m / z 119, C 9 H 11 + ) ions were generated in addition to the molecular ion. Moreover, investigating the production routes to [M−H] + and [M+CH] + ions using a resonance ejection method in the ion trap indicating that generation of these ions was related to the hydride transfer reaction of C 7 H 7 + with p -xylene. Results from the calculations of the reaction profile of this transfer using the density functional theory (DFT) method supported the experimental results. [ABSTRACT FROM AUTHOR]

In this study, for the first time, the conformational space of the rice non-symbiotic hemoglobin type 1 (rHb1) was studied as a function of the starting solution pH using trapped ion mobility spectrometry coupled to mass spectrometry (TIMS-MS) and molecular dynamics. Comparison of the charge state distribution, apo to holo form ratio, and the collision cross section (Ω) profiles as a function of the solution pH showed higher stability of the rHb1 wild-type (WT) when compared with the H73L mutant at mildly acidic conditions. Comparison of the Ω profiles of the rHb1 WT and H73L holo and apo form showed that only the initial unfolding pathways involved the heme cavity, with and without a heme loss, followed by unfolding pathways not necessarily involving the environment of the heme prosthetic group. Candidate structures for the nine transitions observed in the Ω profiles were proposed using molecular dynamic simulations based on the Ω profiles, UV absorption spectroscopy and circular dichroism data as way to describe a potential unfolding pathway. The described unfolding pathway suggests that the rHb1 unfolding is driven by initial distancing of the A, B, and H helices, while the heme cavity and heme group remains intact, followed by the distancing of the E, F, and G helices and subsequent loss of the α-helical structure leading to a final random coil conformation. [ABSTRACT FROM AUTHOR]

In this study we explored the capacity of a mass spectrometry technique, ToF-SIMS, coupled with an immunological method, Dot-ELISA, to characterize the organic binders used in a 13th century painted wooden panel. The panel, which was in a poor state of conservation with only some residual painting left, was a useful bench specimen for these techniques. ToF-SIMS and Dot-ELISA results both indicated the presence of a mixture of rabbit glue and casein and rule out the use of egg in the painted layer of the samples. The results of this study show the capability of the combined use of the two methods to univocally identify protein-based binders in paintings. [ABSTRACT FROM AUTHOR]

Quantitative proton-transfer-reaction mass spectrometer (PTR-MS) measurements of ambient volatile organic compounds (VOCs) require proper calibration procedures. In particular, compound product ion distribution and humidity-dependent responses must be characterized. In this study, we generated twelve gas-phase terpenoid standards using a dynamic dilution system to calibrate the PTR-MS with time-of-flight mass spectrometer (PTR-ToF-MS): six monoterpenes, two monoterpene derivatives, and four sesquiterpenes. The humidity-dependent response was characterized for three terpenoid compounds to compare different molecular structures: α-pinene, δ-limonene, and longifolene. We provide the first comprehensive summary of PTR-ToF-MS product ion distributions for twelve common biogenic volatile organic compounds using two different reduced electric field (E/N) values, 80 Td and 130 Td. Results demonstrated that neglecting to correct for individual product ion distributions of different terpenoid isomers can result in an error of up to 26% for reported mixing ratios. δ-Limonene and longifolene exhibited a small humidity-dependent response in the PTR-ToF-MS, but this did not contribute significantly to the overall measurement error. These results will improve quantification of commonly-measured biogenic volatile organic compound emissions and chemistry in the atmosphere. [ABSTRACT FROM AUTHOR]

The efficiency of collision induced dissociation (CID) is strongly dependent on the ion activation energy. In order to increase the ion kinetic energy during resonance ion excitation, a DC voltage was deduced by simply changing the duty cycle of digital power supply in this study using a digital linear ion trap. In this experiment, different DC potentials were obtained by choosing different duty cycles of main ion trapping digital waveform, and the waveforms applied to the x and y electrode pairs were kept complimentary during ion activation and CID period. The experimental results shown that the CID efficiency was significantly increased when the DC potential was increased. The observed ion internal energy was increased about 2.5 times, and the CID efficiency was increased from 68% to 93%. A calculation shows that the low mass cut off can also be reduced by 15% and it is in agreement with the experiment results. [ABSTRACT FROM AUTHOR]

Curve fitting is the most utilized technique to measure peak areas in time of flight secondary ion mass spectrometry (TOF-SIMS) spectra. Reliable estimations of peak parameters should be provided. However, there is not currently a reliable method to estimate the half-width of spectral peaks. In this study, we present a method for peak detection in TOF-SIMS spectra, incorporating continuous wavelet transform and curve fitting. The half-width was estimated by derivative spectrometry based on continuous wavelet transform. Accurate parameters of each peak were obtained by subsequent curve fitting. The method was evaluated with simulated and real TOF-SIMS spectra of silicon isotopes. The results showed this proposed method obtained more accurate half-width estimations of spectral peaks. The fitted results also showed that the method has better performance on overlapping peaks and better resistance to noise. [ABSTRACT FROM AUTHOR]

Single-valued summaries, such as signal-to-noise ratio, are insufficient to fully describe the input and output characteristics of time-of-flight mass spectra preprocessing methods. A detailed understanding of uncertainty, biases and correlations is essential for selecting appropriate methods, and for drawing confident scientific conclusions from preprocessed data. We apply a range of diagnostic tests to mass spectra, allowing statistical and systematic sources of uncertainty to be assessed throughout the typical stages of a preprocessing pipeline. Baseline correction, alignment and peak detection are reconsidered, with an emphasis on producing outputs with statistical properties compatible with an independent Poisson ion counting process. Benchmarking is also performed against a range of alternative preprocessing methods. In contrast to other preprocessing methods, new techniques are presented which provide improved statistical stability. The benefits are demonstrated using simulation and also data from the RELAX (refrigerator-enhanced laser analyser for xenon) mass spectrometer. A twofold improvement in accuracy of Xe peak measurement over the original method for the same dataset is observed. [ABSTRACT FROM AUTHOR]

The paper summarizes original developments of gridless ion mirrors for high-resolution multi-reflection time-of-flight mass spectrometers (MR TOF MS). Optimized mirror geometries and electrostatic field distributions reach up to the 5th order isochronicity with respect to the energy spread and up to the 3rd order full isochronicity per energy, spatial and angular spreads of ion packets. Using a retarding focusing field at the mirror entrance doubles the ion transport energy at limited highest voltages. In planar analyzers with a zig-zag ion path, quasi-planar mirrors eliminate the 2nd order dependence of the flight time on the ion packet width in the drift direction. Improved MR TOF analyzers of 1 m size provide well over one million aberration limit at realistic ion packets parameters past orthogonal accelerators. Because of high order isochronicity the aberration limit rapidly grows with the analyzer size or when using narrower ion packets. In experiments, improved analyzers with one meter size demonstrate up to 300 000 mass resolving power at the full mass range and 500 000 at the restricted mass range. Improved ion mirrors with two-dimensional electrostatic fields are applicable for TOF MS, electrostatic traps and open electrostatic traps in planar and hollow cylindrical geometries. [ABSTRACT FROM AUTHOR]

Yacon [ Smallanthus sonchifolius (Poepp. et Endl.) H. Robinson] is a plant grown worldwide originating in the Andes region. Yacon is grown for its sweet tuberous roots and leaves used for the preparation of herbal infusions. Twenty-six yacon landraces’ leaves and roots (both peeled and unpeeled) have been analysed by DART-TOF/MS. The method has been optimised and the fingerprints of the mass spectra have been statistically processed by PCA and LDA statistical analysis. The DART method has succeeded in differentiating between the yacon landraces according to their genotype and geographical origin. [ABSTRACT FROM AUTHOR]

Multi-reflection time-of-flight (MR-ToF) devices are established as mass separators and analyzers with high resolving powers and fast processing times. For ion injection and ejection, either the ion mirrors or an in-trap lift electrode has to be switched. In the present work, these two methods are combined with in-trap lift switching for ion capture and exit-side mirror switching for ejection with higher information content. Measurements are performed with small lead clusters to illustrate individual advantages of both techniques and the gain of combining them with focus on the ions’ ToF ejection window. [ABSTRACT FROM AUTHOR]

We probed neutral 2,5-dihydroxy benzoic acid (DHB) crystals in the matrix-assisted laser desorption/ionization (MALDI) plume using ultraviolet (UV) laser post-ionization at 266 nm to investigate the initial MALDI process involving fast phase transitions. Mainly three ion signals, DHB+, [DHB–H 2 O]+ produced by the dissociative ionization of neutral DHB, and [DHB–CO 2 ]+ formed by pyrolysis in the dense plume, were detected using time-of-flight mass spectrometry. The [DHB–H 2 O]+/DHB+ ratio was utilized as the fraction of highly excited neutral DHB molecules produced by photoexcitation and survived after phase explosion, and the [DHB–CO 2 ]+/DHB+ ratio indicated the extent of pyrolysis of neutral DHB molecules in the thermally heated condensed phase before phase explosion. The two indexes showed an inverse relationship with respect to the laser delay corresponding to the position in the plume, i.e., the [DHB–H 2 O]+/DHB+ ratio revealed high values at the tip of the plume, whereas the [DHB–CO 2 ]+/DHB+ ratio increased in the rear part of the plume, reflecting the molecular dynamics of solid-to-gas phase transition involving the production of most MALDI analyte ions. [Display omitted] • MALDI plume of 2,5-dihydroxybenzoic acid was post-ionized with a UV laser. • The tip of the MALDI plume had a high ratio of highly excited neutral molecules. • Neutral molecules at the rear of the MALDI plume were thermally relaxed. • The inhomogeneity exists owing to phase explosion in the desorption mechanism. [ABSTRACT FROM AUTHOR]

Dactylorhiza hatagirea D. Don is acclaimed for different medicinal properties but a little is known about its secondary-metabolites. The purpose of this study was to reveal the components of D. hatagirea by UPLC−ESI/TQ-MS approach. Metabolite profiling of D.hatagirea is reported for the first time for rapid identification of bioactive components. Molecular mass of twelve compounds were determined from LC-MS analysis of the different fractions and structures of five compounds were elucidated with MS/MS fragmentation pattern analysis. Dactylorhin C (2), B (3), A (5), and Loroglossin (4) were derivatives of 2,3-dihydroxy-2-(2-methylpropyl)butanedioic acid and 2-hydroxy-2-(2-methylpropyl)butanedioic acid. In addition, Sucrose (1) was also identified. The obtained results confirmed the presence of Dactylorhins, Loroglossin and Sucrose which have already been isolated from the plant. [Display omitted] • Dactylorhiza hatagirea is a highly valued medicinal orchids from Himalaya. • Structural characterization of some components of D. hatagirea were revealed by LC MS/MS. • Dactylorhins and Loroglossin were important marker compounds noticed in tubers of D. hatagirea. [ABSTRACT FROM AUTHOR]

This work discusses general principles of high-resolution linear time-of-flight (TOF) mass spectrometers across a wide m/z range. Conventional instrument designs are unable to offer adequate performance across a wide m/z range due to inappropriate calculation. Based on big data analyses conducted using comprehensive flight-time topological calculations, high mass resolving power (R m) is available when instrument dimensions and extraction parameters satisfy several preconditions. The result indicates that a longer flight distance does not necessarily provide higher R m. The possibility to achieve high R m for ions of m/z range 100–100,000 are high when the relative length of extraction and acceleration regions to overall instrument length satisfies specific ratios that distinct from conventional designs. With adequate instrument dimensions, achieving optimal R m needs to optimize the voltages and extraction delay in the ion source. Simulation shows that a 900 mm-long instrument of ideal design can enhance R m by more than 250 times (to the order of >100,000) in comparison to the extreme condition of conventional design for ions of m/z 100,000. This general principle can be applied to other TOF instruments of different sizes. The method to finding the ultimate parameters is thoroughly described. [Display omitted] • Comprehensive theoretical principle of high-resolution linear MALDI-TOFMS in wide m/z ranges is described. • Optimum dimension ratios of three major sections of instrument for different m/z ranges are determined for the first time. • Experimental parameters providing high resolution in various m/z ranges are specified. • Limitations in conventional design and practical applications are analyzed. [ABSTRACT FROM AUTHOR]

Monitoring the illegal trade of wool fibres of wild vicuña (Vicugna vicugna) and guanaco (Lama guanicoe) is highly desirable. The high market value of fleece from these camelid species poses a threat to their wild populations. A previous study showed that direct analysis in real time time-of-flight mass spectrometry (DART-TOFMS) effectively identifies wool fibres to species. Producing high-resolution data in a short period of time makes DART-TOFMS a reliable identification tool, even though data analysis can still be improved. The present study proposes a novel data analysing pipeline based on Convolutional Neural Networks (CNN), applicable to any kind of DART-TOF MS data. We tested our proposed method on keratin fibres of four camelid species (Vicugna vicugna : n = 19; Vicugna pacos : n = 20; Lama guanicoe : n = 20, and Lama glama : n = 20). Analyses showed that selecting 512 ions with the highest relative intensity provides the best resolution and yields 100% accuracy for species identification. [Display omitted] • DART-TOFMS identifies wool fibers in camelid species effectively. • CNNs accurately recognize endangered camelid wool patterns. • CNNs expedite DART-TOFMS data processing with minimal preprocessing. [ABSTRACT FROM AUTHOR]

Cell growth and division are important processes for life. To understand the distribution and behaviors of the key molecules that dominate the cell growth and division still remains a challenge. Herein, we propose a strategy for visualization of newly synthesized proteins by TOF-SIMS coupled with metabolic incorporation of 15 N labelled amino acids during the cell growth. Moreover, we simultaneously image phosphatidylcholine and cholesterol during the cell division, since TOF-SIMS is especially suitable for this kind of molecules. With the proposed strategy, 2-dimension and 3-dimension images of proteins and lipids are obtained during cell division. We found that phosphatidylcholine was widely distributed in the cleavage furrow while the newly synthesized proteins exist few in this region. This technique will be a valuable tool to study the molecular behaviors and their spatial distribution in single cell. [ABSTRACT FROM AUTHOR]

Modern analytical techniques are playing increasingly important roles in archaeology. In the field of textile archaeology, the characteristics of silk and dyes are important since they may provide essential information on the origin of the material, dyeing techniques, and even historical windows in understanding trading routes of ancient textiles. Here, we first identify the ancient Chinese textiles from Qing Dynasty Royal Palace as silk fibroin by ATR-spectrum, then extraction conditions for dyestuff on textiles were evaluated as it have quite an effect on the analytical results in the chemical analysis, the extract was analyzed by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC-Q-Tof MS) to identify the natural dyes in these ancient textiles. The results showed that a gentle extraction method (MeOH/FA/EDTA) was efficient and berberine, flavonoids and indigo were identified simultaneously in extracts of ancient textiles by high-resolution mass spectrometry. By comparing extraction profiles of pigments in plants as the likely dye sources by UHPLC-Q-TOF MS, we identified Sophora japonica L. and Phellodendron amurense Rupr. as the dye sources in historical silk fibres. The analyses suggest that the bright yellow textiles were likely dyed with a combination of these two plants and aluminium was used as mordant in the dyeing process. The experiment of color restoration confirmed our analysis. This study demonstrated its ability to identify the dyeing technology of ancient China and provide valuable data for the reparation of historical textiles preserved in the Palace Museum, Beijing. [ABSTRACT FROM AUTHOR]

One of the most common volatile organic compounds (VOCs) group is monoterpenes. Monoterpenes share the molecular formula C 10 H 16 , they are usually cyclic and have a pleasant smell. The most common monoterpenes are limonene (present in citrus fruits) and α-pinene (present in conifers’ resin). Different monoterpenes have different chemical, biological and ecological properties thus it is experimentally very important to be able to differentiate between them in real time. Real time instruments such as Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS), offer a real time solution for monoterpene measurement but at the cost of selectivity resulting in all monoterpenes being seen at the same m / z . In this work we used Selective Reagent Ion-Time of Flight-Mass Spectrometry (SRI/PTR-ToF-MS) in order to explore the differences in ion branching when different ionizations (H 3 O + , NO + and O 2 + ) and different drift tube reduced field energies (E/N) were used. We report a comprehensive ion library with many unique features, characteristic for individual monoterpenes. [ABSTRACT FROM AUTHOR]

Cardenolides are natural products with positive inotropic and cytotoxic activity that are able to interact with metals, although the possible role that these interactions may play in their biological activity is not known. Mixtures of the following cardenolides: digoxigenin (DgG), gitoxigenin (GxG), digitoxigenin (DxG), uzarigenin (UzG) and a butenolide, 2(5H)-furanone (Fur), with different metal cations, namely Ca 2+ , Mg 2+ , Cu 2+ , Co 2+ and Zn 2+ ,were studied by Electrospray Ionization Mass Spectrometry in a Quadrupole-Time of Flight. The relative stability of the most important adducts was studied by threshold collision induced dissociation, E 1/2 . Computational modeling of the observed complexes with calcium was performed using DFT B3LYP/6-31G+(d,p) level of theory. Complexes of stoichiometry [nM+Me] 2+ , with n = 4 to 6 ligands and Me a metal cation, were observed for all studied compounds. The adducts [4M+Me] 2+ corresponded to the most intense peaks in most of the mass spectra and showed the highest E 1/2 . GxG showed a higher tendency to form complexes with low coordination numbers. Calculations showed that the carbonyl oxygen of the butenolide moiety is the most important site of coordination and allowed the proposal of different binding modes to explain the differences observed in the GxG MS spectra. A direct relationship was observed between experimental and computational data, which allowed to predict the MS behavior of these or similar compounds. The analysis can be extrapolated to other compounds with a furanone ring, and used as an analytical tool to characterize furanone compounds, or for the differentiation of DgG and GxG. [ABSTRACT FROM AUTHOR]

This study aimed to perform metabolite profiling of steroidal glycosides in the rhizome of Aspidistra sichuanensis using liquid chromatography coupled with a quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF MS). Steroidal glycosides are one of the largest classes of plant natural products with structural diversity and significant bioactivities. This study summarized the fragmentation rules of six major groups of saponins from Aspidistra . The fragment ions provided a wealth of structural information indicative of the sugar types and number, connecting sequence of sugar units, and types of aglycones. Based on the exact mass information, reliable molecular formulas of the detected compounds could be predicted, and fragmentation ions generated in MS E spectra together with the retention times of the peaks and the structures of steroidal glycosides isolated from the plants belonging to the family Convallariaceae, the structures of 60 constituents were tentatively identified from A. sichuanensis . Also, 34 potential new compounds and 15 pairs of isomers were discovered. [ABSTRACT FROM AUTHOR]

The liquid chromatography hybrid ion trap time-of-flight mass spectrometry (LCMS-IT-TOF) combined with a global identification strategy was applied to studying the protostane triterpenoids (PTs) in the rhizomes of Alisma orientalis in this paper. Initially, the MS n analyses of four reference compounds were performed to summarize the fragmentation rules of PTs. Subsequently, a series of ions of PTs were presented by LC–MS n analyses of the crude extract of alismatis rhizome, from which six ions at m / z 339, 353, 365, 381, 383 and 397 with high frequency of occurrence were selected as diagnostic ions to classify the peaks. Twenty peaks were classified into six families based on common ions. A network was established for the six families via diagnostic ions. 20 PTs including 1 new compound and 19 known ones were characterized through such strategy, fragmentation rules and references. Ultimately, the detected new compound and two known compounds were isolated from the total extract of A. orientalis under the guide of above method, of which the new compound was identified as 11-deoxylalisol F by MS and NMR spectrum. This systematical investigation on the PTs demonstrated that such a strategy could be widely used in the analysis and separation of natural products. [ABSTRACT FROM AUTHOR]

A Wiley–McLaren-type time-of-flight mass spectrometer is improved for ions spatially spread over the ion-extraction region. We examine the case where a continuous ion beam is introduced coaxially to the flight path. The mass resolution, M /Δ M , is degraded because the ions are extensively spread along the flight path, when a conventional linear electric field is applied to the extraction region. It is pointed out that this is mainly due to the fact that the ions initially located near the exit of the extraction region arrive much earlier than the others as revealed by flight-time simulation. The simulation further identifies an ‘ideal’ nonlinear electric field, which compensates for the flight-time difference and thus maximizes the mass resolution. We demonstrate that such a nonlinear electric field close to the ‘ideal’ one is materialized by simply removing a grid mesh from the exit electrode of the extraction region, which results in significant improvement in the mass resolution. [ABSTRACT FROM AUTHOR]

Stability of naphthalene and two of its nitrogen containing derivatives namely, quinoline and isoquinoline are investigated under high energy electron impact. Astro-biologically important statistical dissociation channels are probed using the delayed extraction time-of-flight mass spectrometry technique. The experimental configuration was designed to avoid yield variation due to the thermal velocities for 5 μs or more after the collision. The statistical decay channels show an increase in the yield of daughter ions as a function of extraction delay in the range of 10 6 s −1 . On the other hand, the yields due to fast dissociation channels were observed to decrease as a function of extraction delay. On the basis of projectile beam energy dependence of the yields, the effect of plasmon excitation in quinoline and isoquinoline is shown for the first time. A strong dependence of the statistical dissociation yield on the location of the nitrogen atom in the two molecules is observed. An attempt is made to correlate these observations with the various structure parameters obtained using structure calculations. [ABSTRACT FROM AUTHOR]

A new method is presented for making the overall flight path of ions in a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) isochronous. Here, the ions undergo an arbitrary number of turns in a TOF analyzer, which itself is tuned to be isochronous from turn to turn. The overall isochronicity from the ion source or injection trap to the detector is established by changing the voltage settings of the analyzer dynamically to a different mode for one turn. This approach combines the advantages of an MR-TOF-MS with a time focus shift reflector with the simplicity of an MR-TOF-MS with only the TOF analyzer as an isochronous tool. Measurements have been performed, in which an MR-TOF-MS was operated with this dynamical time focus shift. These are compared to measurements, in which the time focus was shifted onto the detector using a variation of the extraction field strength in the injection trap. A mass resolving power was achieved that is up to three times larger for the same time-of-flight. For Cs ions, mass resolving powers of 100,000 and 200,000 were obtained after flight times of 1.7 ms and 4.9 ms, respectively. These flight times are a factor of 3 shorter than those with the time focus shift with the injection trap. The smaller number of turns required for a given mass resolving power results in a larger unambiguous mass range, a higher transmission efficiency, a higher ion capacity and a shorter measurement time. This yields advantages in precision experiments in nuclear physics and for applications in analytical mass spectrometry. [ABSTRACT FROM AUTHOR]

The present work reports on cationization characteristics of organic molecules in alkali metal environment. Samples of arginine and polyethylene glycol polymers with average masses of 600, 1000 and 1500 were mixed with sodium- and potassium trifluoroacetate of various concentrations, and analyzed through secondary ion mass spectrometry. Bombardment proceeded with ions within both keV and MeV energy domains. Added salts positively affected the secondary ion yield through attachment of Na or K to organic molecule. Ionization differences between swift (MeV) ions and cluster ions, commonly used for secondary ion mass spectrometry analysis, were studied for arginine and PEG 600. While for arginine, secondary ion yield enhancement was only by a factor of 2, when analysing with MeV ions, and no enhancement was observed with keV Bi 3 clusters, all polyethylene glycol samples showed increase of the secondary ion yield by factors between 3 and 40, depending on the amount of potassium or sodium that was mixed into the matrix. Additionally, higher amounts of salts also resulted in decreased fragmentation probability for organic molecules, reducing the intensities of specific fragments by more than two orders of magnitude. [Display omitted] • Added salts significantly increase secondary ion yield for both keV and MeV primary ions. • Ionization increase due to salt addition is greater with keV SIMS. • Added matrix reduces fragmentation – more with MeV-SIMS. • With secondary ion yields of approx. 10−2, submicron molecular imaging is feasible. [ABSTRACT FROM AUTHOR]

Influenza is a contagious respiratory illness caused by influenza viruses which possess the enormous threat to older people and young children. Rapid and precise discrimination of virus subtypes are quite crucial for the early therapy, prophylaxis and the prevention of epidemic outbreaks. Herein, a universal strategy, with influenza A virus (IAV) as a model, is proposed for the discrimination of virus subtypes based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Reference library based on nine IAVs subtypes (i.e., H1N1, H3N2, H4N8, H5N8, H6N6, H7N7, H9N2, H10N8, and H11N8) was set up for matching various IAVs subtypes. The simulative test spectra from IAVs showed that the corresponding IAVs subtypes could be distinguished in 90 min, accurately. Furthermore, the principal component analysis results also show that nine virus subtypes can be reliably distinguished. More importantly, this strategy provides an alternative method for identifying and distinguishing other viruses with high variability characteristics, such as SARS-CoV-2, which could be helpful for implementing public health strategies to counter pandemics. A MALDI-TOF MS based universal strategy for the discrimination of virus subtypes was developed, which possess the advantages of speed and high-accuracy. [Display omitted] • A home-made identification database of influenza A virus subtypes was set up. • The discrimination of influenza A virus subtypes could be finished within 90 min. • The influenza A virus subtypes could be distinguished with high accuracy. [ABSTRACT FROM AUTHOR]

The increasing prevalence of designer drugs has contributed towards the adoption of rapid screening techniques, such as direct analysis in real time-mass spectrometry (DART-MS). Recently, the National Institute of Standards and Technology (NIST) developed a DART-MS Forensics Database and Data Interpretation Tool (DIT) to assist practitioners with the interpretation of seized drug mixtures. However, this resource was only designed for DART ionization coupled with AccuTOF high-resolution mass spectrometers. This study assesses the effectiveness of the NIST DART-MS Forensics Database and DIT for mixture interpretation using other soft ionization sources, such as electrospray ionization (ESI), and coupling DART to an Agilent 6530 quadrupole time-of-flight (Q-TOF) mass spectrometer. As the seized drug community continues to shift towards the use of in-source collision-induced dissociation (IS-CID) with single-stage mass spectrometers coupled with soft ionization sources, it is imperative to understand the similarity of the generated IS-CID fragment ion spectra and the effectiveness of the DIT for seized drug screening using instrumentation other than the DART-AccuTOF. Pearson product-moment correlations (PPMCs) revealed a high degree of spectral similarity between the ESI-IS-CID and DART-IS-CID fragment ion spectra collected across a range of activation conditions. The 95% confidence interval for the average highest PPMC coefficient across the 12 designer drugs in this study was 0.9295 ± 0.0031. More importantly, nearly identical mixture interpretation results were obtained when the ESI-IS-CID and DART-IS-CID fragment ion spectra were analyzed with the DIT. In all cases, the DIT was able to identify a potential library match with at least two match types between the low and high IS-CID spectra for all compounds present in each mixture. Demonstrating the potential applicability of the NIST DART-MS Forensics Database and DIT for the screening of seized drug mixtures using instrumentation other than the DART-AccuTOF provides support for the expanded applicability of this freely available resource. [Display omitted] • ESI- and DART-generated IS-CID spectra are highly comparable. • NIST DIT is compatible with IS-CID spectra from non-DART AccuTOF instrumentation. • Support for expanded applicability of the NIST DART-MS Forensics Database and DIT. • Similar screening results for drug mixtures using ESI- and DART-IS-CID spectra. • Proposed criteria to maximize the value of NIST DIT screening results. [ABSTRACT FROM AUTHOR]

The thermal decomposition mechanism of trimethylchlorosilane at temperatures up to 1400 K was investigated using flash pyrolysis microreactor coupled with vacuum ultraviolet (118.2 nm) photoionization time-of-flight mass spectrometry. The main initiation reaction of the parent molecule was identified to be HCl molecular elimination producing Me 2 Si=CH 2 , and its onset temperature was estimated to be around 1210 K. The methyl loss channel was also observed at an onset temperature of ∼1280 K. Other possible initiation pathways such as chlorine atom loss and methane molecular elimination were considered to be insignificant. Quantum chemistry calculations at the UCCSD(T)/cc-pVTZ//UM05–2X/aug-cc-pVDZ level of theory were performed to study the energetics of the possible initiation pathways. The theoretical calculations revealed that the HCl elimination channel via a van der Waals intermediate was the most energetically favored pathway among all the initiation channels, in agreement with the experimental observations. Transition state theory (TST) and variational transition state theory (VTST) calculations were employed to calculate unimolecular dissociation rate constants of the initiation reactions at elevated temperatures. The results supported the experimental observations and reaction energetics calculations that the HCl molecular elimination reaction was the most prominent initiation reaction and the CH 3 loss channel was a significant initiation reaction channel. Secondary reactions of the initial products were identified, and the possible mechanisms were proposed. [Display omitted] • Trimethylchlorosilane decomposes mainly via molecular elimination to form HCl and Me 2 Si = CH 2. • Trimethylchlorosilane undergoes bond homolysis reaction, losing methyl radical. • The energetics and the unimolecular rate constants for the initiation reactions are calculated. [ABSTRACT FROM AUTHOR]

Malaria, worldwide, affects around 500 million people with 2–3 million clinical cases every year. In this study, a proteomic approach was used to analyze the alterations in mice serum proteome induced by P. berghei infection; and identified number of differentially expressed proteins compared to control. Serum proteins were separated by two-dimensional electrophoresis (2DE). These proteins were further identified by matrix-assisted laser desorption or ionization – time-of-flight (MALDI-TOF) spectrometry. Important proteins identified include Serum amyloid A4 protein, Kelch-like protein, Glutathione-S-transferase Mu1. The identified proteins could have a significant role in developing a biomarker-based diagnostic tool for malaria. [ABSTRACT FROM AUTHOR]

A series of 2,3′-bisindolylmethanes were analyzed using electrospray ionization quadrupole time-of-flight and radical ions ([M] + ) and dehydro cations ([M−H] + ) were detected in positive-ion mode. The formation pathways of [M] + were proposed confirmed by D-labeling, free radical trapping and CID-MS/MS experiments. It was found that [M] + ion was formed in droplets by the direct loss of an electron and the processes forming [M] + and [M−H] + ions were independent. The fragmentation pathways of the [M−H] + and [M] + ions were studied by CID-MS/MS. The dominant fragmentation pattern of [M] + ions is the loss of benzyl radical comparing to that of [M−H] + ions. [ABSTRACT FROM AUTHOR]

The use of the 90° hemispheric electrostatic high resolution analyzer in conjunction with the time-of-flight (TOF) technique allowed us to identify various species associated with the ionization of methane molecular gas by a pulsed fast 19 MeV F 4+ beam. We were able to measure the yields of single and double ionization-dissociation species of H + , H 2 + , C + , C 2+ , CH + , C H 2 + , C H 3 + , C H 4 + and C H 4 2 + . We reported the single- and total ionization cross sections of C H 4 + and the daughter ions- C H 3 + , C H 2 + , CH + and C + . Our results show that the single ionization cross sections of C H 4 + and C H 3 + are in good accord with those found in literature, however, the cross sections of C H 2 + , CH + and C + are in disagreement with the ones found in literature. [ABSTRACT FROM AUTHOR]

A new method including two sub-procedures, global search and local refine, has been developed and presented to design a multiple-reflection time-of-flight (MRTOF) mass analyzer. By using this method, a different type of MRTOF mass analyzer, in which each mirror consists of five cylindrical electrodes, has been designed for isobaric separation for Lanzhou Penning Trap (LPT). The optimal potential parameters of the electrodes have been obtained and the maximal resolving power has been achieved to be 1.3 × 10 5 with a total time-of-flight of 6.5 ms for an ion species of Ar 1 + 40 . The simulation shows that the inaccuracy of the potentials applied to the mirror electrodes must be less than 50 ppm or preferably 20 ppm. [ABSTRACT FROM AUTHOR]

It is experimentally challenging to generate nano-sized metal oxide clusters with significant intensity as well as to resolve a single hydrogen atom by mass spectrometry (TOF-MS). Herein, the high-resolution tandem time-of-flight mass spectrometer is home-made and the experimental apparatus is capable to perform the reactivity study of nano-sized vanadium oxide clusters. The formation and distribution of nano-sized vanadium oxide cluster anions V x O y − ( x up to 70) were analyzed and the photoreaction of alkene attached complex V 40 O 101 C 2 H 4 − (or V 40 O 101 C 3 H 6 − ) was studied. Larger V x O y − cluster anions can be generated typically under higher O 2 concentration and the intensity proportion (%) of vanadium oxide cluster with a certain oxygen-deficiency value Δ (Δ= 2 y -5 x -1 for V x O y − ) in each V x series is nearly invariant. In photoreaction of V 40 O 101 C 2 H 4 − (or V 40 O 101 C 3 H 6 − ), the transfer of two oxygen atoms from V 40 O 101 − to C 2 H 4 (or C 3 H 6 ) and the generation of V 40 O 99 − dominants the channel. The mass resolution of the primary TOF-MS for V 40 O 101 − (∼1.5 nm) is up to 13002. The mass resolution of the secondary TOF-MS for photoreaction is calculated to be about 4530 to resolve parent (V 40 O 101 C 2 H 4 − ) and daughter ions (V 40 O 99 − ). [ABSTRACT FROM AUTHOR]

An orthogonally accelerated time-of-flight mass spectrometer has been added to a flowing afterglow–Langmuir probe apparatus, coupled by a rectilinear ion guide. The TOF has improved the signal-to-noise (S/N) ratio by about an order of magnitude over a quadrupole mass filter/electron multiplier detection typical for flow tube instruments of this type and used previously. The improved S/N reduces our data acquisition time commensurately. Additionally, mass discrimination is low enough that it is minimal for ions heavier than ∼10 amu. The lack of mass discrimination not only reduces experiment time but also leads to greater accuracy in the measurement of reaction rate coefficients. Finally, simultaneous detection of both heavy and light ions is improved. H + can now be detected and WF 5 + isotopes can be separated without reducing sensitivity. We have found that discrimination against low-mass ions can occur when certain electron-attaching reactants are used (e.g. SF 6 ), and possibly due to radicals formed after certain other reactants attach electrons. Evidence points to adsorption of these species on surfaces of the ion guide immediately behind the flowing afterglow sampling orifice, which separates the flow tube and TOF region. The adsorption follows a Langmuir isotherm profile and is greatly reduced by heating the gas in the flow tube. [ABSTRACT FROM AUTHOR]