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As seized drug casework becomes increasingly complex due to the continued prevalence of emerging drugs, laboratories are often looking for new analytical approaches including developing methods for the analysis of specific compounds classes. Recent efforts have focused on the development of targeted gas chromatography mass spectrometry (GC-MS) confirmation methods to compliment the information-rich screening results produced by techniques like direct analysis in real time mass spectrometry (DART-MS). In this work, a method for the confirmation of synthetic opioids and related compounds was developed and evaluated. An 11-component test solution was used to develop a method that focused on minimizing overlapping retention time acceptance windows and understanding the influence of instrument parameters on reproducibility and sensitivity. Investigated settings included column type, flow rate, temperature program, inlet temperature, source temperature, and tune type. Using a DB-200 column, a 35-min temperature ramped method was created. It was evaluated against a suite of 222 synthetic opioids and related compounds, and successfully differentiated all but four compound pairs based on nonoverlapping retention time acceptance windows or objectively different mass spectra. Compared to a general confirmatory method used in casework, the targeted method was up to 25 times more sensitive and provided at least a two-fold increase in retention time differences. Analysis of extracts from actual case samples successfully demonstrated utility of the method and showed no instance of carryover, although the high polarity column required wider retention time windows than other columns.

Because of its speed, sensitivity, and ability to scrutinize individual species, mass spectrometry (MS) has become an essential tool in analytical strategies aimed at studying the degradation behavior of polyesters. MS analyses can be performed prior to the degradation event for structural characterization of initial substrates or after it has occurred to measure the decreasing size of products as a function of time. Here, we show that MS can also be usefully employed during the degradation process by online monitoring the chain solvolysis induced by reactive desorption electrospray ionization (DESI). Cleavage of ester bonds in random copolymers of lactic acid (LA) and glycolic acid (GA) was achieved by electrospraying methanol-containing NaOH onto the substrates. Experimental conditions were optimized to generate methanolysis products of high abundance so that mass spectra can be conveniently processed using Kendrick-based approaches. The same reactive-DESI performance was demonstrated for two sample preparations, solvent casting for soluble samples or pressed pellets for highly crystalline substrates, permitting to compare polymers with LA/GA ratios ranging from 100/0 to 5/95. Analysis of sample fractions collected by size exclusion chromatography showed that methanolysis occurs independently of the original chain size, so data recorded for poly(LA-co-GA) (PLAGA) copolymers with the average molecular weight ranging from 10 to 180 kDa could be safely compared. The average mass of methanolysis products was observed to decrease linearly (R2 = 0.9900) as the GA content increases in PLAGA substrates, consistent with the susceptibility of ester bonds toward solvolysis being higher in GA than in LA. Because DESI only explores the surface of solids, these data do not reflect bulk degradability of the copolymers but, instead, their relative degradability at the molecular level. Based on a "reactive-DESI degradability scale" such as that established here for PLAGA, the proposed method offers interesting perspectives to qualify intrinsic degradability of different polyesters and evaluate their erosion susceptibility or to determine the degradability of those polymers known to degrade via erosion only.

The infrared (IR) spectra of the O-H stretching vibrations of pyridine-water clusters (Pyd)m(H2O)n, with m, n = 1-4, have been investigated with infrared-vacuum ultraviolet (VUV) spectroscopy under a jet-cooled condition. The time-of-flight mass spectrum of (Pyd)m(H2O)n+ by VUV ionization at ∼9 eV showed an unusual intensity pattern with very weak ion signals for m = 1 and 2 and stronger signals for m ≥ 3. This unusual mass pattern was explained by a drastic structural change of (Pyd)m(H2O)n upon the VUV ionization, which was followed by the elimination of water molecules. Among the recorded IR spectra, only one spectrum monitored, (Pyd)2+ cation, showed a well-resolved structure. The spectrum was analyzed by comparing with the simulated ones of possible stable isomers of (Pyd)2(H2O)n, which were obtained with quantum-chemical calculations. Most of the calculated (Pyd)2(H2O)n clusters had the characteristic structure in which H2O or (H2O)2 forms a hydrogen-bonded bridge between two pyridines to form the π-stacked (Pyd)2, and an additional H2O molecule(s) extends the H-bonded network. The π-stacked (Pyd)2(H2O)n moiety is very stable and is thought to exist as a local structure in a pyridine/water mixed solution. The Fermi resonance between the O-H stretch fundamentals and the overtones of the O-H bending vibrations in (Pyd)m(H2O)n was found to be less pronounced in the case of (Pyd)m(NH3)n studied previously.

Pyridazine nuclei are essential elements of many natural and synthetic compounds with important biological activities. NMR and IR, as well as studies of mass spectrum, were emplyed to synthesize an...

Metaproteomics is a powerful analytical approach that can assess the functional capabilities deployed by microbial communities in both environmental and biomedical microbiome settings. Yet, the mass spectra resulting from these mixed biological communities are challenging to obtain due to the high number of low intensity peak features. The use of multiple dimensions of chromatographic separation prior to mass spectrometry analyses has been applied to proteomics previously but can require increased sampling handling and instrument time. Here, we demonstrate an automated online comprehensive active modulation two-dimensional liquid chromatography method for metaproteome sample analysis. A high pH PLRP-S column was used in the first dimension followed by low pH separation in the second dimension using dual modulating C18 traps and a C18 column. This method increased the number of unique peptides found in ocean metaproteome samples by more than 50% when compared to a one-dimension separation while using the same amount of sample and instrument time.

A two-dimensional MoS2 nanosheet was prepared by a chemical exfoliation method and served as an excellent matrix for the detection of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). In comparison with organic matrices (CHCA, 3-AQ) and a graphene matrix, we found that a MoS2 matrix showed better performance in analysis of amino acids, peptides, fatty acids, and sulfonamides. A systematic comparison of the MoS2 matrix with both ion modes showed that mass spectra produced in negative ion mode featured a corresponding single deprotonated ion, which was rather different from the complex multiple alkali metal addition peaks present in positive ion mode. In addition, better sensitivity and reproducibility were obtained in negative ion mode. The ionization mechanism of MoS2 as a matrix in negative ion mode was further discussed. The deproton peak intensity of the analyte fatty acid decreased after the addition of the hole-scavenger KSCN, indicating that the ionization of the fatty acid was caused by the Auger complex effect of MoS2 and electron injection. Experiments have shown that the MoS2 matrix detects small molecules with good repeatability and can perform semiquantitative analysis of sulfonamides. Finally, the MoS2 matrix was employed for quantitative determination of sulfamethoxine in serum samples by an internal standard method. This MoS2-assisted laser desorption/ionization mass spectrometry (MoS2-assisted LDI MS) method provides a simple, rapid, high-throughput approach to evaluate the drug levels in the patient serum and can achieve convenient drug therapy monitoring.

High resolution electrospray time-of-flight mass spectrometric analysis was applied as a guiding tool for selection of the chlorine containing fractions by their characteristic clusters of isotopic molecular ion peaks in mass spectra. Twelve target-compounds, chlorinated aromatic glycosides were carried out and identified from the methanolic extract of Hypoxis aurea tubers by chromatographic methods. Hypoxichlorosides A–F (3, 6, 9−12) were found to be undescribed compounds. Curculigine A (1), curculigine B (2), curculigine E (4), curculigine J (5), 2,4,6-trichloro-3-methoxy-5-methylphenyl 1-O-β- d -glucopyranosyl-(1→6)-β- d -glucopyranoside (7) and curculigine C (8) were isolated for the first time from this species. The structure determinations were considered based on the spectroscopic evidence including 1D and 2D NMR experiments.

High-resolution mass spectrometry (MS) has advanced the study of metabolism in living systems by allowing many metabolites to be measured in a single experiment. Although improvements in mass detector sensitivity have facilitated the detection of greater numbers of analytes, compound identification strategies, feature reduction software, and data sharing have not kept up with the influx of MS data. Here, we discuss the ongoing challenges with MS-based metabolomics, including de novo metabolite identification from mass spectra, differentiation of metabolites from environmental contamination, chromatographic separation of isomers, and incomplete MS databases. Because of their popularity and sensitive detection of small molecules, this review focuses on the challenges of liquid chromatography-mass spectrometry–based methods. We then highlight important instrumentational, experimental, and computational tools that have been created to address these challenges and how they have enabled the advancement of metabolomics research.

Polymerization of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane is the main method for manufacturing methylphenylsiloxane rubbers, and copolymerization of octamethylcyclotetrasiloxane and 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane is the main method for production of high- and low-molecular weight dimethylmethylphenylsiloxane rubbers. The molecular weight, viscosity, and other properties of the obtained polymers depend on the purity of cyclosiloxanes. The technology of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane production by thermocatalytic decomposition of methylphenylsiloxanes in the presence of lithium hydroxide or lithium silanolate, followed by vacuum rectification, makes it possible to obtain a product containing 1,3,5,7-tetramethyl-1,3,5,7-tetraphenylcyclotetrasiloxanes, tetraphenyldimethyldisiloxane as impurities and trace amounts of phenyl-containing siloxanes of cyclic and linear structure. The impurities of polycyclic and polyhedral structures have not been previously described. In this study, the method of gas chromatography-mass spectrometry is used to analyze compounds that can be present as impurities in technical-grade 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane. The use of the previously described regularities of the fragmentation of siloxanes of different structures made it possible to identify a number of siloxanes which are absent in the NIST 11 mass spectra library. It is shown that polycyclic and polyhedral compounds containing methylsilsesquioxane units have a short fragmentation path. They are characterized by ionization with the elimination of the methyl group and benzene in case of two phenyl groups in the molecule. The siloxane skeleton of such cations is rather stable, so they more readily lose another methyl group thus transforming into double-charged cations. The impact of electron ionization on the molecules with siloxane units containing different organic substituents at silicon leads to randomization of those substituents and rearrangement of the siloxane skeleton. Analysis of the results revealed that silanes, siloxanes of linear, cyclic, polycyclic and polyhedral structures are present in technical grade 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane.

Structure elucidation is one of big tasks for analytical researcher and it often needs an efficient classifier. The decision tree is especially attractive for easy understanding and intuitive represen- tation. However, small change in the data set due to the experiment error can often result in a very different series of split. In this pa- per, a prior logarithm normal distribution is adopted to weight the original mass spectra. It helps to building an honest tree for later structure elucidation.

The high-throughput identification of unknown metabolites in biological samples remains challenging. Most current non-targeted metabolomics studies rely on mass spectrometry, followed by computational methods that rank thousands of candidate structures based on how closely their predicted mass spectra match the experimental mass spectrum of an unknown. We reasoned that the infrared (IR) spectra could be used in an analogous manner and could add orthologous structure discrimination; however, this has never been evaluated on large data sets. Here, we present results of a high-throughput computational method for predicting IR spectra of candidate compounds obtained from the PubChem database. Predicted spectra were ranked based on their similarity to gas-phase experimental IR spectra of test compounds obtained from the NIST. Our computational workflow (IRdentify) consists of a fast semiempirical quantum mechanical method for initial IR spectra prediction, ranking, and triaging, followed by a final IR spectra prediction and ranking using density functional theory. This approach resulted in the correct identification of 47% of 258 test compounds. On average, there were 2152 candidate structures evaluated for each test compound, giving a total of approximately 555,200 candidate structures evaluated. We discuss several variables that influenced the identification accuracy and then demonstrate the potential application of this approach in three areas: (1) combining IR and mass spectra rankings into a single composite rank score, (2) identifying the precursor and fragment ions using cryogenic ion vibrational spectroscopy, and (3) the incorporation of a trimethylsilyl derivatization step to extend the method compatibility to less-volatile compounds. Overall, our results suggest that matching computational with experimental IR spectra is a potentially powerful orthogonal option for adding significant high-throughput chemical structure discrimination when used with other non-targeted chemical structure identification methods.

A new approach combining classification tree (CT) with sliced inverse regression (SIR) is proposed and applied to the clas- sification of mass spectra in this paper. The classification tree has been widely used to generate classifiers from the mass spectral data because of its powerful ability in automatic variable selection and automatic interaction detection. However, it is often weak on pre- senting the linear and global relationships among variables. When the variables enter a model with the form of linear combination, the classification tree can not detect the form and leads to a low accuracy. SIR is an effective method to find useful linear combinations of pre- dictor variables to regress the response variable. So merging CT and SIR harmoniously can inherit both advantages of them. Experiments in the paper show that the proposed approach can improve classi- fication accuracy of decision tree and get better result than other classical classification methods.

The aim of the work was the development and validation of a liquid chromatography–tandem mass spectrometry (LC–MS-MS) γ-hydroxybutyrate (GHB) quantification method in urine and human serum by the use of the analyte adduct ion formation strategy. A combined detection with a conventional precursor ion in the negative electrospray mode and additionally GHB adduct ions with both sodium acetate and lithium acetate was in focus. Therefore, GHB quantification was based on separated MS-MS signals. Two tandem mass spectrometers representing different MS-MS generations (Sciex API 4000 QTrap and Sciex API 5500 QTrap) were used for method validation and comparison. Shimadzu HPLC systems equipped with a Luna 5-µm C18 (2) 100 A, 150-mm × 2-mm analytical column were successfully applied for sample analyses. Infusion experiments were performed for adduct identification and analyte detection optimization. Sample preparation could be limited to a simple and fast protein precipitation/sample dilution. An effective signal-separated GHB quantification with three independent precursor ions representing separated areas of the mass spectrum was developed, validated according to forensic guidelines and applied in the routine. The developed and applied strategy resulted in a higher safety factor for the analyte quantification performed in the forensic toxicology. A relevant analytical improvement could be achieved with this alternative adduct-based GHB analysis since a good correlation of analyte concentrations calculated on the basis of separated signals was stated as useful analytical information.

Annotating product ion peaks in tandem mass spectra is essential for evaluating spectral quality and validating peptide identification. This task is more complex for glycopeptides and is crucial for the confident determination of glycosylation sites in glycoproteins. MS_Piano (Mass Spectrum Peptide Annotation) software was developed for reliable annotation of peaks in collision induced dissociation (CID) tandem mass spectra of peptides or N-glycopeptides for given peptide sequences, charge states, and optional modifications. The program annotates each peak in high or low resolution spectra with possible product ion(s) and the mass difference between the measured and theoretical m/z values. Spectral quality is measured by two major parameters: the ratio between the sum of unannotated vs all peak intensities in the top 20 peaks, and the intensity of the highest unannotated peak. The product ions of peptides, glycans, and glycopeptides in spectra are labeled in different class-type colors to facilitate interpretation. MS_Piano assists validating peptide and N-glycopeptide identification from database and library searches and provides quality control and optimizes search reliability in custom developed peptide mass spectral libraries. The software is freely available in .exe and .dll formats for the Windows operating system.

Ion mobility separations (IMS) have increasingly been coupled with mass spectrometry to increase peak capacity and deconvolute complex mass spectra in proteomics workflows. IMS separations can be integrated prior to or following the collisional activation step. Post-activation IMS separations have demonstrated many advantages, yet few instrument platforms are capable of this feat. Here, we present the fragmentation of peptide ions within a commercially available trapped-ion mobility spectrometry device. Fragmentation is initiated prior to mobility analysis enabling the separation of generated product ions. The added separation step deconvolutes product ion spectra and permits improved annotation of product ions. Furthermore, we demonstrate the isolation and fragmentation of mobility separated product ions with the downstream quadrupole and collisional cell. When applied to melittin and ubiquitin, this ion mobility assisted pseudo-MS3 fragmentation approach generates sequence coverage ∼50% greater than that of typical MS2 analyses. We envision this ion-mobility-assisted fragmentation technique as the foundation of a powerful new pseudo-MS3 workflow for application toward middle- or top-down proteomics.

An efficient synthesis of fluorinated [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives has been achieved by cyclocondensation of 5-substituted 4-amino-1,2,4-triazole-3-thiols with fluoro-substituted aromatic acids using phosphoryl chloride as a cyclizing agent. The synthesized compounds were characterized by spectroscopic techniques, including IR, 1H NMR, and mass spectra.

Chemistry - a European journal 27(48), 12371 - 12379 (2021). doi:10.1002/chem.202101515, We investigated the photoionization and fragmentation of isolated metal protoporphyrin IX cations (MPPIX+ with M=Fe, Co, Zn) by means of vacuum-ultraviolet (VUV) action spectroscopy in the energy range of 8.5���35 eV. Experiments were carried out in the gas phase by interfacing an electrospray ionization tandem mass spectrometer with a synchrotron beamline. The mass spectra and partial ion yields show that photoexcitation of the precursor ions predominantly leads to .CH$_2$COOH radical side-chain losses of the macrocycle with additional methyl radical (.CH$_3$) side-chain losses. Ionization, in contrast, leads to the formation of the intact ionized precursor and various doubly charged fragments which are mostly due to side-chain cleavages. Although statistical fragmentation dominates, we found evidence for non-statistical processes such as new fragments involving for example single and double H2O losses, indicating that different relaxation mechanisms are at play upon photoionization compared to photoexcitation. The measured ionization energies were 9.6��0.2 eV, 9.4��0.2 eV and 9.6��0.2 eV for FePPIX$^+$, CoPPIX$^+$ and ZnPPIX$^+$, respectively., Published by Wiley-VCH, Weinheim

New hydrazinylidene derivatives were synthesized under appropriate conditions and in excellent yields, by the reaction between a new [1,3]thiazolo[3,2-a]benzimidazol-2(3H)-one substrate and a series of aryldiazonium salts bearing groups with different electronic effect. The structures of the synthesized compounds were verified by FT-IR, 1H NMR and mass spectra. The pharmacological study including determining antimicrobial activity, cytotoxicity LD50 and histological study for compound ethyl 4-[(2Z)-2-(2-oxo[1,3]thiazolo[3,2-a] benzimidazol-3(2H)-ylidene)hydrazinyl]benzoate have been fulfilled. All chemical and biological result show possibility of using the compound ethyl 4-[(2Z)-2-(2-oxo[1,3]thiazolo[3,2-a] benzimidazol-3(2H)-ylidene)hydrazinyl]benzoate as a new topical antibiotic.

Looking at the previous studies on quinazolinones derivatives, only limited information’s are available on their mass spectral along with the preparation of novel quinazolin-4-(3H)-one derivatives The condensation of Methyl-2-amino-4-Chlorobenzoate with acetic anhydride yielded the cyclic compound 2-methyl 7-Chloro-1, 3-benzo-oxazine-4-one (1) which further produce 3-Amino-2-Methyl 7-Chloro quinazolin-4(3H)-ones (2) via the reaction with hydrazine hydrate. The compounds synthesized were unequivocally confirmed by means of Infrared, Nuclear Magnetic Resonance (1H and 13C), Gas Chromatography-Mass spectrophotometry and Elemental analysis. Discussion: The molecular ion of m/z 235 fragments to give m/z 220 by loss of –NH group. The ion of m/z 220 was broken to give m/z 206 by losing CH2 group and fragment to m/z 177 by loss of HCO. This fragmented to m/z 162 by loss of –CH3 group and then m/z 136 by loss of CN group. The loss of O gave m/z 120 which fragment to give m/z 93 by loss of –HCN and finally gave m/z 65 by loss of CO group. Conclusion: The electron impact ionization mass spectra of compound 2show a weak molecular ion peak and a base peak of m/z 235resulting from a cleavage fragmentation. Compound 2 give a characteristic fragmentation pattern. From the study of the mass spectra of compound 2, it was found that the molecular ion had fragmented to the m/z 220. The final fragmentation led to ion of m/z 93 and ion of mass m/z 65, respectively

Supertetrahedral clusters have been reported in two generally different types so far: one type possessing an organic ligand shell, no or low charges, and high solubility, while the other cluster type is ligand‐free with usually high charges and low or no solubility in common solvents. The latter is a tremendous disadvantage regarding further use of the clusters in solution. However, as organic substituents usually broaden the HOMO–LUMO gaps, which cannot be overcompensated by the (limited) cluster sizes, a full organic shielding comes along with drawbacks regarding opto‐electronic properties. We therefore sought to find a way of generating soluble clusters with a minimum number of organic substituents. Here, we present the synthesis and full characterization of two salts of [Sn10O4S16(SBu)4]4− that are high soluble in CH2Cl2 or CH3CN, which includes first NMR and mass spectra obtained from solutions of such salts with mostly inorganic supertetrahedral clusters. The optical absorption properties of this new class of compounds indicates nearly unaffected band gaps. The synthetic approach and the spectroscopic findings were rationalized and explained by means of high‐level quantum chemical studies., Selective access to partially butylated supertetrahedral clusters [Sn10O4S16(SBu)4]4− was achieved by employing a di‐butylated ionic liquid as reaction medium and alkylation agent. In contrast to purely inorganic [Sn10O4S20]8−, the butylated analogs are soluble in solvents like CH2Cl2 or CH3CN, without losing the typical opto‐electronic properties. Solution‐NMR data were assigned with the help of newly developed all‐electron relativistic DFT methods.

We present simple considerations of how differences in time scales of motions of protons, the lightest and fastest chemical moiety, and the much longer time scales associated with the dynamics of proteins, among the heaviest and slowest analytes, may allow many protein conformations from solution to be kinetically trapped during the process of electrospraying protein solutions into the gas phase. In solution, the quantum nature of protons leads them to change locations by tunneling, an instantaneous process; moreover, the Grotthuss mechanism suggests that these small particles can respond nearly instantaneously to the dynamic motions of proteins that occur on much longer time scales. A conformational change is accompanied by favorable or unfavorable variations in the free energy of the system, providing the impetus for solvent ↔ protein proton exchange. Thus, as thermal distributions of protein conformations interconvert, protonation states rapidly respond, as specific acidic and basic sites are exposed or protected. In the vacuum of the mass spectrometer, protons become immobilized in locations that are specific to the protein conformations from which they were incorporated. In this way, conformational states from solution are preserved upon electrospraying them into the gas phase. These ideas are consistent with the exquisite sensitivity of electrospray mass spectra to small changes of the local environment that alter protein structure in solution. We might remember this approximation for the protonation of proteins in solution with the colloquial expression—protons are fast and smart; proteins are slow and dumb.

We investigate the extent to which comprehensive three-dimensional gas chromatography (GC3) provides a signal enhancement (SE) and a signal-to-noise ratio enhancement (S/NRel) relative to one-dimensional (1D)-GC. Specifically, the SE is defined as the ratio of the tallest 3D peak height from the GC3 separation to the 1D peak height from the unmodulated 1D-GC separation. A model is proposed which allows the analyst to predict the theoretically attainable SE (SET) based upon the peak width and sampling density inputs. The model is validated via comparison of the SET to the experimentally measured SE (SEM) obtained using total-transfer GC3 (100% duty cycle for both modulators) with time-of-flight mass spectrometry detection. Two experimental conditions were studied using the same GC3 column set, differing principally in the modulation period from the 1D to 2D columns: 4 s versus 8 s. Under the first set of conditions, the average SEM was 97 (±22), in excellent agreement with the SET of 97 (±18). The second set of conditions improved the average SEM to 181 (±27), also in agreement with the average SET of 176 (±26). The average S/NRel following correction for the mass spectrum acquisition frequency was 38.8 (±11.2) and 59.0 (±27.2) for the two sets of conditions. The enhancement in S/N is largely attributed to moving the signal to a higher frequency domain where the impact of "low frequency" noise is less detrimental. The findings here provide strong evidence that GC3 separations can provide enhanced detectability relative to 1D-GC and comprehensive two-dimensional gas chromatography (GC×GC) separations.

The coordination between a ligand and a metal is a spontaneous and uncontrollable process. In this Article, we successfully observe the formation of metal coordination in a triphenylamine-functionalized salicylaldehyde Schiff base with a copper(II) ion. The ligand TPA-Py first reacts with Cu2+ in a stepwise process to afford the dynamic complex TPA-Py@Cu2+ ([ligand]:[Cu2+] = 1:1), which further reacts with an extra copper(II) ion to afford 2TPA-Py@4Cu2+ with the following stepwise (or cumulative) stability constants: K1 = 4.0694 × 103 and K2 = 1.0761 × 106, respectively. The entire metal coordination process can be visualized, and the coordination mode of the probe toward copper was further evaluated by ultraviolet-visible/fluorescence spectra, single-crystal X-ray diffraction, density functional theory calculations, high-resolution mass spectra, and nuclear magnetic resonance spectroscopic titrations. Compound TPA-Py exhibited excellent sensitivity and specificity toward copper(II) ions in THF/water media with a low limit of detection of 2.687 × 10-7 mol L-1. In addition, TPI-An-Py can be applied to the detection of Cu2+ in real samples with satisfactory recoveries in the range of 100-112% in lake water and 98-101% in tap water. This Article not only reports an excellent fluorescence probe for copper(II) ion detection but also presents an instance for more fully understanding the metal coordination process.

Phytochemical investigations of Blumea balsamifera branches and leaves led to the isolation of ten secondary metabolites, including three new compounds, namely, balsamiferine K (1) and balsamiferosides A (2) and B (3). Structural elucidation was confirmed by detailed analysis of the 1D and 2D NMR spectra as well as HR-ESI-QTOF mass spectra. Among the isolated compounds, blumeaene J (4) exhibited moderate cytotoxicity against LNCaP (IC50 = 44.53 ± 4.95 μM) and SK-Mel2 (IC50 = 46.49 ± 3.84 μM) cell lines and weak effects on HepG2 (IC50 = 61.54 ± 2.98 μM), KB (IC50 = 65.40 ± 4.97 μM), and MCF-7 (IC50 = 70.06 ± 5.65 μM) cell lines, whereas (―)-angelicoidenol 2-O-β- d -glucopyranoside (6) revealed weak activity on all five tested cancer cell lines, with IC50 values ranging from 61.60 ± 5.64–98.73 ± 2.24 μM.

New benzimidazole derivatives were synthesized by reacting substituted phenacyl bromides with 1H-benzimidazole-2-thiols. The synthesized compounds were characterized through 1H and 13C NMR and high-resolution mass spectra. Their evaluation for α-amylase activity revealed inhibitory potential with IC50 values ranging from 1.20±0.05 to 19.10±0.30 μM against IC50 = 1.70±0.10 μM for the standard drug acarbose. Among the examined series, 2-[(1H-benzimidazole-2-yl)sulfanyl]-1-(3–nitrophenyl)ethan-1-one (IC50 = 1.20±0.05 µM) was the most potent. Other nitro-substituted analogs showed good potency with IC50 values of 2.10±0.10, 2.20±0.10 and 2.10±0.10 µM. Limited structure–activity relationship was established for all derivatives based on the nature, position, and number of substituents on the aryl ring. Binding sites of the most active compounds were determined by the molecular docking study.

Journal of cosmology and astroparticle physics 12(12), 006 (2022). doi:10.1088/1475-7516/2022/12/006, We study the generation of a localized peak in the primordial spectrum of curvature perturbations from a transient dissipative phase during inflation, leading to a large population of primordial black holes. The enhancement of the power spectrum occurs due to stochastic thermal noise sourcing curvature fluctuations. We solve the stochastic system of Einstein equations for many realizations of the noise and obtain the distribution for the curvature power spectrum. We then propose a method to find its expectation value using a deterministic system of differential equations. In addition, we find a single stochastic equation whose analytic solution helps to understand the main features of the spectrum. Finally, we derive a complete expression and a numerical estimate for the energy density of the stochastic background of gravitational waves induced at second order in perturbation theory. This includes the gravitational waves induced during inflation, during the subsequent radiation epoch and their mixing. Our scenario provides a novel way of generating primordial black hole dark matter with a peaked mass distribution and a detectable stochastic background of gravitational waves from inflation., Published by IOP, London

The LHCb Collaboration has recently discovered a structure around 6.9 GeV in the double-$J/\psi$ mass distribution, possibly a first fully-charmed tetraquark state $X(6900)$. Based on vector-meson dominance (VMD) such a state should have a significant branching ratio for decaying into two photons. We show that the recorded LHC data for the light-by-light scattering may indeed accommodate for such a state, with a $\gamma \gamma$ branching ratio of order of $10^{-4}$, which is larger even than the value inferred by the VMD. The spin-parity assignment $0^{-+}$ is in better agreement with the VMD prediction than $0^{++}$, albeit not significantly at the current precision. Further light-by-light scattering data in this region, clarifying the nature of this state, should be obtained in the Run 3 and probably in the high-luminosity phase of the LHC (Run 4 etc.)., Comment: 6 pages, 4 figures

Modern soft ionization mass spectrometry provides chemical information on various polymers with unparalleled resolution and sensitivity. However, the interpretation of the resulting highly complex mass spectra is hampered by the sheer amount of contributing macromolecular species. For example, state-of-the-art reversible deactivation radical polymerization techniques, which are generally considered to be highly controlled, can still generate tens or even hundreds of species in a narrow mass window. Moreover, the multitude of species typically leads to partially overlapping isotopic patterns, further complicating the data evaluation. Herein, a rapid and powerful three-step methodical approach is introduced that enables the successful identification and quantification of the contributing species. The approach is subsequently implemented in “pyMacroMS”, a high performance algorithm that allows for ultrafast processing of high resolution polymer mass spectra with varying complexities. The power of our algorithm is demonstrated on the example of a photochemical atom transfer radical polymerization (photoATRP) of three monomers, ultimately leading to 908 identified species. pyMacroMS is available free of charge under a GNU General Public License v3.0.

Intact phase II steroid metabolites have poor product ion mass spectra under collision-induced dissociation (CID) conditions. Therefore, we present herein the liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/(MS)) behavior of intact phase II metabolites of oxosteroids after derivatization. Based on the fact that Girard's reagent T (GRT), as derivatization reagent, was both convenient and efficient in terms of the enhancement in the ionization efficiency and the production of diagnostic product ions related to the steroid moiety, the latter was preferably selected between methoxamine and hydroxylamine upon the model compounds of androsterone glucuronide and androsterone sulfate. Sixteen different glucuronides and 29 sulfate conjugated metabolites of anabolic androgenic steroids (AASs), available either as pure reference materials or synthesized/extracted from administration studies, were derivatized with GRT, and their product ion spectra are presented. Product ion spectra include in all cases high number of product ions that in some cases are characteristic for certain structures of the steroid backbone. More specifically, preliminary results have shown major differences in fragmentation pattern for 17α/17β-isomers of the sulfate conjugates, but limited differentiation for 17α/17β-isomers of glucuronide conjugates and for 3α/3β- and 5α/5β-stereoisomers of both sulfate and glucuronide conjugates. Further to the suggestion of the current work, application on mesterolone administration studies confirmed-according to the World Anti-Doping Agency (WADA) TD2015IDCR-the presence of seven intact phase II metabolites, one glucuronide and six sulfates with use of LC-ESI-MS/(MS).

© Trapped ion-mobility spectrometry combined with quadrupole time-of-flight mass spectrometry (TIMS-QTOFMS) was evaluated as a tool for resolving linear and branched isomeric polyester oligomers. Solutions of polyester samples were infused directly into the ion source employing electrospray ionization (ESI). TIMS-MS provides both mobility and m/z data on the formed ions, allowing construction of extracted-ion mobilograms (EIMs). EIMs of polyester molecules showed multimodal patterns, indicating conformational differences among isomers. Subsequent TIMS-MS/MS experiments indicated mobility differences to be caused by (degree of) branching. These assignments were supported by liquid chromatography-TIMS-MS/MS analysis, confirming that direct TIMS-MS provided fast (500 ms/scan) distinction between linear and branched small oligomers. Observing larger oligomers (up to 3000 Da) using TIMS required additional molecular charging to ensure ion entrapment within the mobility window. Molecular supercharging was achieved using m-nitrobenzyl alcohol (NBA). The additional charges on the oligomer structures enhanced mobility separation of isomeric species but also added to the complexity of the obtained fragmentation mass spectra. This complexity could be partly reduced by post-TIMS analyte-decharging applying collision-induced dissociation (CID) prior to Q1 with subsequent isolation of the singly charged ions for further fragmentation. The as-obtained EIM profiles were still quite complex as larger molecules possess more possible structural isomers. Nevertheless, distinguishing between linear and symmetrically branched oligomers was possible based on measured differences in collisional cross sections (CCSs). The established TIMS-QTOFMS approach reliably allows branching information on isomeric polyester molecules up to 3000 Da to be obtained in less than 1 min analysis time.

Organic pollutants can be identified by comparing their electron ionization (EI) mass spectra with those in libraries or obtained from authentic standards. Nevertheless, libraries are incomplete; standards may be unavailable or too costly, or their synthesis may be too time-consuming. This study evaluates the performance of quantum chemical electron ionization mass spectrometry (QCEIMS) vis-a-vis competitive fragmentation modeling (CFM) for suspect screening and unknown identification. EI mass spectra of 35 compounds, including halogenated organics, organophosphorus flame retardants (OPFRs), and disinfection byproducts were computed. Computational results were compared with EI mass spectra compiled in the NIST Library as well as collision-induced dissociation (CID) mass spectra obtained from radical cations M•+ generated by charge-exchange atmospheric pressure chemical ionization (APCI). The results indicate that QCEIMS performs equivalently or better than CFM. Average match factors between computed and experimental (NIST) EI mass spectra were 656 vs 503 for the halogenated organics, and on average, QCEIMS predicted 55% of the products generated by CID vs 17% predicted by CFM. QCEIMS predicted 37% of the OPFR CID products whereas CFM predicted 29%. QCEIMS performed comparably to a commercial combinatorial fragmentation method for suspect screening of a dust sample, identifying 19/20 targets. Examples of unknown pollutants, whose reference spectra were unavailable at the time of discovery, are also presented. The computational results suggest that QCEIMS can help guide the analyst in obtaining authentic standards and raise the possibility that, with advances in computing, an unknown may eventually be confirmed in hours as opposed to the days or months required to obtain authentic standards.

In this work, the electrochemical determination of antioxidant compounds in green coffee beans using a low-pressure chromatographic system based on a single 1-cm length monolithic column is presented. Screening of the antioxidant compounds in green coffee beans using this approach was performed under different elution conditions, considering different supporting electrolyte media and applied potential values at detection. Mass spectra analyses for the structure elucidation of the separated compounds are presented. Under the selected experimental conditions, five chlorogenic acids (3-, 4-, 5-, cis-5-caffeoylquinic acids, and 5-feruloylquinic acid) and caffeine were identified. Resolution values higher than 1.5 were achieved for all identified compounds. The limits of detection for 5-caffeoylquinic acid and caffeine were 9.25 µmol L−1 and 6.73 µmol L−1, respectively. Acetonitrile consumption was of 0.325 mL per analysis. The figures of merit obtained plus the simplicity of the analytical system assembling and handling highlight the high competitiveness of the presented low-cost approach to be used in substitution of HPLC methodologies currently performed to this end, and for further analytical applications in complex matrices.

Background Objective of present research work is to develop and validate cost-effective analytical tool for determination of camptothecin (CPT) and determine its anticancer potential against prostate cancer LNCaP cell lines. Structural elucidation has been performed by mass spectrometry, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and MTT assay utilized for in vitro cytotoxicity where spectrometric method was used for estimation of camptothecin. Results Mass spectra showed peak at 349.2 which matches to standard molecular weight of camptothecin. FTIR and NMR spectra conformed functional moieties and structure of isolated camptothecin which was nearly equal to values mentioned in standard structure of camptothecin. IC50 values of CPT against LNCaP cell lines was found to be 3.561 μg/ml. Lambda max of CPT was found to be at 225 nm and calibration curve found to be linear over the concentration range from 2 to 70 μg/ml of camptothecin. Developed method was found to be linear, accurate, and precise. LOD and LOQ were found to be 0.0524 μg/ml and 0.1614 μg/ml, respectively. Developed method has % relative standard deviation less than one which is reproducible hence % recovery was found to be 99.80%. Conclusions FTIR, NMR, and mass spectrometry results conforms isolated compound was camptothecin; cytotoxicity study proves it has strong potential in treatment of prostate carcinoma as competent alternative to chemotherapy in the form of herbal medicine and the developed UV method proves to be valid, sensitive, and applicable for rapid, accurate, precise, and economical determination of camptothecin.

We present the calculated and the experimental mass spectra of alkali metal tungstates within the temperature range of 1100–1500 K and determine the vapor pressures and the thermodynamic properties of gaseous alkali metal tungstates.

In this study, the imaging of metal ions and nanoparticles deposited on a structured silicon surface was investigated using a laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). For application, 8 $\times $ 8 Petri-dish pillars, each with a diameter of 250 $\mu \text{m}$ and height of 300 $\mu \text{m}$ , were constructed on a silicon wafer. The etched pillar surface took a droplet of approximately 4.3 nL aqueous solution from a capillary tip through the surface-liquid attraction. The dissolved materials were found at the intersecting edge of pillar bottom after evaporation, and their positions were matched with the peaks of elements in the mass spectrum for imaging. Results suggest that the trace contaminants in the cleaning solution are gathered at the intersecting edges of the patterned wafer, and the multi-elemental images of the contaminants can be successfully obtained using LA-ICP-MS.

Particulate organic nitrates (pON) are an important component of secondary organic aerosol in biogenic-emission-dominant environments and play a critical role in NOx cycles. However, estimation of pON has been a challenge in polluted environments, e.g., North China Plain, with high concentrations of inorganic nitrate and NOx. Here we developed a method for estimation of pON from the measurements of high-resolution aerosol mass spectrometer coupled with a thermodenuder based on the volatility differences between inorganic nitrate and pON. The results generally correlated well with those estimated from positive matrix factorization of combined organic and inorganic mass spectra and from the ratio of NO+ to NO2+ (NOx+ ratio), yet they had improvements in reducing negative values due to the influences of high concentration of inorganic nitrate and constant NOx+ ratio of organic nitrates (RON). By applying this approach to the measurements at an urban (Beijing) and a rural site (Gucheng) in summer and winter in the North China Plain, we estimated that the average mass concentrations of NO3,org (1.8 µg m−3 vs. 1.0 µg m−3) and pON to OA (27.5 % vs. 14.8 %) were higher in summer than in winter in Beijing, indicating more pON formation in biogenically and anthropogenically mixed environments. In addition, the average NO3,org loading in Gucheng was 1.9 µg m−3, and the pON at the rural site also showed higher contribution to OA than that in Beijing during wintertime due to higher primary emissions and gaseous precursors in Gucheng. In addition, RON was determined and showed considerable differences between day–night and clean–polluted periods, highlighting the complexity of pON compounds from different chemical pathways (e.g., OH and NO3 oxidation) and sources.

The kinetics of intercluster metal atom exchange reactions between solvated [Ag25(DMBT)18]- and [Au25(PET)18]- (DMBT and PET are 2,4-dimethylbenzenethiol and 2-phenylethanethiol, respectively, both C8H10S) were probed by electrospray ionization mass spectrometry and computer-based modeling. Anion mass spectra and collision induced dissociation (CID) measurements show that both cluster monomers and dimers are involved in the reactions. We have modeled the corresponding kinetics assuming a reaction mechanism in which metal atom exchange occurs through transient dimers. Our kinetic model contains three types of generic reactions: dimerization of monomers, metal atom exchange in the transient dimers, and dissociation of the dimers to monomers. There are correspondingly 377 discrete species connected by in total 1302 reactions (i.e., dimerization, dissociation and atom exchange reactions) leading to the entire series of monomeric and dimeric products [AgmAu25-m]- (m = 1-24) and [AgmAu50-m]2- (m = 0-50), respectively. The rate constants of the corresponding reactions were fitted to the experimental data, and good agreement was obtained with exchange rate constants which scale with the probability of finding a silver or gold atom in the respective monomeric subunit of the dimer, i.e., reflecting an entropic driving force for alloying. Allowing the dimerization rate constant to scale with increasing gold composition of the respective reactants improves the agreement further. The rate constants obtained are physically plausible, thus strongly supporting dimer-mediated metal atom exchange in this intercluster reaction system.

Electron-based dissociation (ExD) produces uncluttered mass spectra of intact proteins while preserving labile post-translational modifications. However, technical challenges have limited this option to only a few high-end mass spectrometers. We have developed an efficient ExD cell that can be retrofitted in less than an hour into current LC/Q-TOF instruments. Supporting software has been developed to acquire, process, and annotate peptide and protein ExD fragmentation spectra. In addition to producing complementary fragmentation, ExD spectra enable many isobaric leucine/isoleucine and isoaspartate/aspartate pairs to be distinguished by side-chain fragmentation. The ExD cell preserves phosphorylation and glycosylation modifications. It also fragments longer peptides more efficiently to reveal signaling cross-talk between multiple post-translational modifications on the same protein chain and cleaves disulfide bonds in cystine knotted proteins and intact antibodies. The ability of the ExD cell to combine collisional activation with electron fragmentation enables more complete sequence coverage by disrupting intramolecular electrostatic interactions that can hold fragments of large peptides and proteins together. These enhanced capabilities made possible by the ExD cell expand the size of peptides and proteins that can be analyzed as well as the analytical certainty of characterizing their post-translational modifications.

Precursor compounds (PCs) link quantum dots (QDs) and magic-sized clusters (MSCs), which is pivotal in the conversion between QDs and MSCs. Here, for the first time, we report the transformation, synthesis, and composition of a type of ZnSe PCs. ZnSe PCs can be directly transformed to two different MSCs with the assistance of octylamine and acetic acid at room temperature. The two types of MSCs exhibit sharp absorption peaks at 299 and 328 nm which are denoted as MSC-299 and MSC-328. In the preparation of ZnSe PCs, diphenylphosphine (DPP) as an additive plays a key role which not only inhibits the thermal decomposition of Zn precursor, but also acts as a reducing agent to reduce the by-products produced in the reaction. The composition was explored by X-ray photoelectron spectroscopy, energy dispersive spectrometer, matrix-assisted laser desorption/ionization time-of-flight mass spectra with ZnSe PC powder appeared as white powder after purifying by toluene (Tol) and methanol (MeOH). The results indicate that the molar ratio of Zn/Se is 2:1 with a molecular of ∼ 3,350 Da. Therefore, we propose that the molecular formula of ZnSe PCs is Zn32Se16. In addition, at the molecular level, the covalent bond of Zn-Se is formed in ZnSe PCs. This study offers a deeper understanding of the transformation from PCs to MSCs and for the first time proposes the composition of PCs. Meanwhile, this research provides us with a new understanding of the role of DPP in the synthesis of colloidal semiconductor nanoparticles.

In this work, we obtain solutions of the Schrödinger equation with Kratzer-screened Coulomb potential (KSCP) model using the series expansion method. Explicitly, we compute the bound state energy eigenvalues for selected diatomic molecules of N2, CO, NO, and CH, respectively, for the various vibrational and rotational quantum states and the numerical energy eigenvalues agree with the existing literature. Three special cases were considered. The energy eigenvalues are applied to obtain the mass spectra of heavy quarkonium system such as charmonium and bottomonium. The results agree with the experimental data and other recent theoretical studies.

The main features of the secondary emission mass spectrometry probing of condensed systems containing compounds of biological significance at low temperatures are summarized. The possibilities of distinguishing mass spectra of the solid and liquid phases of simple organic compounds and water as the medium for bio-molecules, monitoring of phase transitions and nonequilibrium processes are illustrated. The peculiarities of a model of sputtering of metastable liquids are described. On the basis of the evaluation of these findings, an idea concerning the probable source of relatively large clusters of organic molecules and ions emerging on sputtering of the liquid phase of organic matter condensed on dust grains in space is proposed and discussed.

Here, we newly propose the structure of protoaculeine B, an N-terminal moiety of the marine peptide toxin aculeine B, as possessing the cis-disubstituted tetrahydro-beta-carboline framework. We prepared two truncated model compounds that lack long-chain polyamine by one-step Pictet-Spengler reaction of tryptophan, and compared the NMR and mass spectra and chemical reactivity with those of natural protoaculeine B. The synthetic models reproduced the profiles of the natural product well, which was conclusive for the structural revision.

The Orbitrap mass spectrometer has recently been proved to be a powerful instrument to accurately measure gas-phase and particle-phase organic compounds with a greater mass resolving power than other widely used online mass spectrometers in atmospheric sciences. We develop an open-source software tool (Orbitool, https://orbitrap.catalyse.cnrs.fr, last access: 4 February 2021) to facilitate the analysis of long-term online Orbitrap data. Orbitool can average long-term data while improving the mass accuracy by re-calibrating each mass spectrum, assign molecular formulae of compounds and their isotopes to measured signals, and export time series and mass defect plots. The noise reduction procedure in Orbitool can separate signal peaks from noise and reduce the computational and storage expenses. Chemical ionization Orbitrap data from laboratory experiments on ozonolysis of monoterpenes and ambient measurements in urban Shanghai were used to test Orbitool. For the test dataset, the average mass accuracy was improved from to ppm by mass calibrating each spectrum. The denoising procedure removed 97 % of the noise peaks from a spectrum averaged for 30 min while maintaining the signal peaks, substantially helping the automatic assignment of unknown species. To illustrate the capabilities of Orbitool, we used the most challenging and complex dataset we have collected so far, which consists of ambient gas-phase measurements in urban Shanghai. These tests showed that Orbitool was able to automatically assign hundreds of molecular formulae as well as their isotopes with high accuracy.

The autoxidation of triglyceride (or triacylglycerol, TAG) is a poorly understood complex system. It is known from mass spectrometry measurements that, although initiated by a single molecule, this system involves an abundance of intermediate species and a complex network of reactions. For this reason, the attribution of the mass peaks to exact molecular structures is difficult without additional information about the system. We provide such information using a graph theory-based algorithm. Our algorithm performs an automatic discovery of the chemical reaction network that is responsible for the complexity of the mass spectra in drying oils. This knowledge is then applied to match experimentally measured mass spectra with computationally predicted molecular graphs. We demonstrate this methodology on the autoxidation of triolein as measured by electrospray ionization-mass spectrometry (ESI-MS). Our protocol can be readily applied to investigate other oils and their mixtures.

De novo peptide sequencing is the key technology for finding novel peptides from mass spectra. The overall quality of sequencing results depends on the de novo peptide sequencing algorithm as well as the quality of mass spectra. Over the past decade, the resolution and accuracy of mass spectrometers have improved by orders of magnitude and higher-resolution mass spectra have been generated. How to effectively take advantage of those high-resolution data without substantially increasing the computational complexity remains a challenge for de novo peptide sequencing tools. Here we present PointNovo, a neural network-based de novo peptide sequencing model that can robustly handle any resolution levels of mass spectrometry data while keeping the computational complexity unchanged. Our extensive experiment results show PointNovo outperforms existing de novo peptide sequencing tools by capitalizing on the ultra-high resolution of the latest mass spectrometers. Increased resolution of mass spectroscopy can provide better data for sequencing, but also increases the computational complexity of analysing the data. Qiao and colleagues present here a neural network-based method that processes sequencing data of any resolution while improving the accuracy of predicted sequences.

Here, a new gas chromatography-atmospheric pressure photoionization-high-resolution mass spectrometry (GC-APPI-HRMS) method combined with selective pressurized liquid extraction (sPLE) has been developed for the selective determination of Dechlorane Plus (DP) and its related compounds in gull egg samples used as a bioindicator of contamination. To the best of our knowledge, this is the first time these compounds have been analyzed by GC-MS using atmospheric pressure photoionization (APPI). Negative ion dopant-assisted APPI using vapors of diethyl ether and a source temperature of 250 °C provided high ionization efficiencies and mass spectra characterized by intense in-source fragment ions as well as the presence of molecular ion and characteristic cluster ions containing oxygen atoms in their chemical structure. This made it possible to improve the selectivity in the determination of these compounds compared to that obtained with traditional GC-MS ion sources. Under optimized conditions, the sPLE GC-APPI-HRMS (Orbitrap) method provided high recoveries (> 91%), good precisions (RSD%, This work received financial support from the Spanish Ministry of Science, Innovation and Universities under the project PGC2018-095013-B-I00 and PID2019-105732GB-C21, as well as the Generalitat of Catalonia under the project 2017-SGR-310 and the Spanish Autonomous Organism of National Parks under the project 2012/768. Juan F. Ayala-Cabrera received PhD fellowship from the Spanish Ministry of Education, Culture and Sports (FPU14/05539).

The need for technology and technology has led to a sharp acceleration of experimental design and research work to study in an ultrahigh vacuum environment, both surface and bulk properties of solids. The accumulation of basic knowledge about surfaces, especially semiconductor materials, makes it possible to develop modern semiconductor devices in electronics and microelectronics. In this work, a time-of-flight mass spectrometric setup is proposed, the use of which makes it possible to obtain objective information about such processes as adsorption and desorption on the surface of semiconductors. Mass spectrometry is a physical method for analyzing the composition of complex mixtures of substances and identifying individual substances in them by their mass spectra. The mass spectrum is obtained as a result of ionization of substances, separation of ions according to their mass numbers (the ratio of the mass of an ion to its charge) and measurement of the intensity of ion currents for all ions. The mass spectrum allows conclusions to be drawn about the molecular weight of the sample, its composition and structure. The study of adsorption processes makes it possible to qualitatively change the conditions on the surface of semiconductors, which in turn change the energy spectrum of electrons in the near-surface region and leads to the production of both efficient photocathodes with negative electron affinity and an MIS structure with specified parameters. The novelty of this setup lies in the fact that, along with the existing standard units, blocks and devices (a rectangular pulse generator that controls the power supply of an electron gun, an ion source, an electron multiplier for registering ions by masses, a pulse broadband amplifier, a gate signal delay unit, valve, integrator and indicator) are used in order to increase the speed, accuracy and reliability of measurements. Recommended additionally a waiting square-wave generator, two pulse expanders and a comparison unit, while the input of the waiting square-wave generator is connected to the output of the master pulse generator, and its two outputs are connected to the inputs of pulse expanders, the outputs of which are connected to the inputs of the comparator connected with their output to the stroboscopic signal delay unit, they can qualitatively improve the operation of the installation.

In the past decade, hydrophilic interaction liquid chromatography (HILIC) has emerged as an efficient alternative to reversed-phase chromatography (RPC) for the analysis of phospholipid (PL) mixtures based on mass spectrometric detection. Since the separation of PL by HILIC is chiefly based on their headgroup, the mass spectrum of each class can be obtained by spectral averaging under the corresponding HILIC band. Using experimental m/z values resulting from high mass resolution/accuracy instruments, the sum compositions of PL in a specific class can be thus inferred but partial overlapping may occur between signals related to the M + 0 isotopologue of one species and the M + 2/M + 4 isotopologues of species having one/two more C═C bonds in their chemical structures. Here, an automated workflow, named LIPIC (lipid isotopic pattern interference correction), is proposed to account for such interferences. Starting from the experimentally verified assumption that peaks in isotope patterns are Gaussian, LIPIC predicts, as a function of m/z ratio, signal intensities due to M + 2 and M + 4 isotopologues of species with one or two more C = C bonds than the target one and calculates the corrected intensity for the M + 0 isotopologue of the latter. Thanks to an iterative procedure, the suggested algorithm compensates also for slight shifts occurring between experimental and theoretical m/z ratios related to isotopologue peaks. Examples of applications to simulated and experimental mass spectra of two PL classes, i.e., phosphatidylcholines (PC) and cardiolipins (CL), emphasize the increased extent of correction at the increase of molecular masses of involved species.

Reaction of 2-((4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)methylene)hydrazinecarbothioamides with dimethyl acetylenedicarboxylate afforded, in good yields, the corresponding thiazoles derived from 2-quinolones. However, the reaction of N-ethyl-2-quinonylhydrazinecarbothioamide with 2-(bis(methylthio)methylene)malononitrile or its ester derivative gave the corresponding quinolin-3-yl-methylenehydrazono-1,3-thiazines. The proposed mechanism was discussed. The structure of the obtained products was elucidated via NMR, IR and mass spectra as well as elemental analysis.