Product Identification and Mass Spectrometric Analysis of n-Butane and i-Butane Pyrolysis at Low Pressure

The pyrolysis of n-butane and i-butane at low pressure was investigated from 823-1823 K in an electrically heated flow reactor using synchrotron vacuum ultraviolet photoionization mass spectrometry. More than 20 species, especially several radicals and isomers, were detected and identified from the measurements of photoionization efficiency （PIE） spectra. Based on the mass spectrometric analysis, the characteristics of n-butane and i-butane pyrolysis were discussed, which provided experimental evidences for the discussion of decomposition pathways of butane isomers. It is concluded that the isomeric structures of n-butane and i-butane have strong influence on their main decomposition pathways, and lead to dramatic differences in their mass spectra and PIE spectra such as the different dominant products and isomeric structures of butene products. Furthermore, compared with n-butane,i-butane can produce strong signals of benzene at low temperature in its pyrolysis due to the enhanced formation of benzene precursors like propargyl and C4 species, which provides experimental clues to explain the higher sooting tendencies of iso-alkanes than n-alkanes.

Mass Spectrometric Study of Clusters Produced by Laser Vaporization of Some Phosphates

The clusters generated by direct laser vaporization of KH2PO4 and Cu-3(PO4)(2) samples are studied by a TOF mass spectrometer. It is found that mainly the [K(KPO3)(n)]* cluster series is generated from KH2PO4 sample and it demonstrates obvious magic numbers, which are n=3, 6, 9, 12, 15. Direct laser vaporization of Cu-3(PO4)(2) sample produced [Cu(CuPO3)n]* cluster series as well as other series with the same building block of (CUPO3).

Specific Mass Spectrometric Fragmentations from the Dissociation of Intermediate Ion-Neutral Complexes

It is reported that two kinds of specific mass spectrometric fragmentations are generated from dissociations of the intermediates of both the ion-neutral complex and the proton-bound complex. Collision-induced dissociation, isotopic labelling, and semi-empirical AM1 calculations were used to investigate the formation mechanism of the ion of m/z 139 from ionized tetrahydroimidazole-substituted methylene beta-diketones and the unimolecular fragmentations pathway of 3-phenyl-1-butyn-3-ol upon electron impact.

Determination of Variance of Secondary Metabolites in Lettuces Grown Under Different Light Sources by Flow Injection Mass Spectrometric(FIMS)Fingerprinting and ANOVA-PCA

Lettuce(Lactuca sativa L.)is one of the most consumed vegetables in the world and different management practice can result in considerable variability of the secondary metabolites.Flow injection mass spectrometry(FIMS)combined with analysis of variance-principle component analysis(ANOVA-PCA)was used to study differences in the secondary metabolites originat-ing from different lighting conditions(Sunlight,white light,and florescent light)and lettuce varieties(Romaine and Lollo Rossa).Ultra-high-performance liquid chromatography-high-resolution accurate mass spectrometry was used for putative marker compound identification.Quinic acid,caffeic acid,chlorogenic acid,L-chicoric acid,and quercetin malonyl gluco-side varied significantly for Romaine lettuce grown under different light conditions.The study showed that the combination of FIMS fingerprinting and ANOVA-PCA can be a useful tool for the characterization of the sources of variance in plant materials regarding to genetic,environmental,and management factors.

Mass spectrometric studies of cis- and trans-1a,3-disubstituted-1, 1-dichloro-4-formyl-1a ,2,3,4-tetrahydro-1H-azirino [ 1,2-a] [1,5] benzodiazepines

The mass spectrometric behaviour of four cis- and trans-1a, 3-disuhsdtuted-1,1-dichloro-4-formyl-1a,2,3,4-tetrahydro-1H-azirino[1, 2-a] [1, 5]benzodiazepines has been studied with the aid of mass-analysed ion kinetic energy spectrometry and exact mass measurements under electron impact ionization. All compounds show a tendency to eliminate a chlorine atom from the aziridine ring, and then eliminate a neutral propene or styrene from the diazepine ring to yield azirino[1, 2b][1,3] benzimidazole ions. These azirino[1,2-a][1,5]benzodiazepines can also eliminate HCl, or Cl plus HCl simultaneously to undergo a ring enlargement rearrangement to yield 1,6-benzodiazocine ions, which further lose small molecular fragments, propyne or phenylacetylene, with rearrangement to give quinoxaline ions.

The“depict”strategy for discovering new compounds in complex matrices:Lycibarbarspermidines as a case

The comprehensive detection and identification of active ingredients in complex matrices is a crucial challenge.Liquid chromatography coupled with high-resolution mass spectrometry(LC-HRMS)is the most prominent analytical platform for the exploration of novel active compounds from complex matrices.However,the LC-HRMS-based analysis workflow suffers from several bottleneck issues,such as trace content of target compounds,limited acquisition for fragment information,and uncertainty in interpreting relevant MS2 spectra.Lycibarbarspermidines are vital antioxidant active ingredients in Lycii Fructus,while the reported structures are merely focused on dicaffeoylspermidines due to their low content.To comprehensively detect the new structures of lycibarbarspermidine derivatives,a“depict”strategy was developed in this study.First,potential new lycibarbarspermidine derivatives were designed according to the biosynthetic pathway,and a comprehensive database was established,which enlarged the coverage of lycibarbarspermidine derivatives.Second,the polarity-oriented sample preparation of potential new compounds increased the concentration of the target compounds.Third,the construction of the molecular network based on the fragmentation pathway of lycibarbarspermidine derivatives broadened the comprehensiveness of identification.Finally,the weak response signals were captured by data-dependent scanning(DDA)followed by parallel reaction monitoring(PRM),and the efficiency of acquiring MS2 fragment ions of target compounds was significantly improved.Based on the integrated strategy above,210 lycibarbarspermidine derivatives were detected and identified from Lycii Fructus,and in particular,170 potential new compounds were structurally characterized.The integrated strategy improved the sensitivity of detection and the coverage of low-response components,and it is expected to be a promising pipeline for discovering new compounds.

Detection of Optical Stability of chiral 2-Methylbutyric Acid in Gas Phase with Quadrupole-Quistor-Quadrupole Mass Spectrometer

Optical stability of chiral 2-methylbutyric acid in gas phase has been detected with Quadrupole-Quistor-Quadrupole tandem mass spectrometer in combination with deuteration. The results show that these compounds are optically unstable in the process of self chemical ionization.

Spatial distribution of SiCln （n=O-2） in SICl4 plasma measured by mass spectroscopy

For a better understanding of the deposition mechanism of thin films in SiCl4 source gas, we have measured the spatial distributions of SiCln （n=0-2） radicals in SICl4 radio frequency glow discharge plasma utilizing a mass spectrometer equipped with a movable gas sampling apparatus. The experimental results demonstrate that the relative densities of SiCln （n=0-2） radicals have peak values at the position of 10 mm above the powered electrode along the axial direction; the relative densities of the Si and SiCIn （n=1, 2） radicals have peak values at the positions of 27mm and 7 mm away from the axis along the radial direction, respectively. Generally speaking, in the whole SICl4 plasma bulk region, the relative density of Si is one order of magnitude higher than that of SICl, and the relative density of SiCl is several times higher than that of SICl2. This reveals that Si and SiCl may be the primary growth precursors in forming thin films.

Simultaneous separation and determination of four main isoflavonoids in Astragali Radix by an isocratic LC/ESI-MS method

A simple, reliable and rapid isocratic liquid chromatography(LC)-mass spectrometric detection(MS) coupled with electrospray ionization(ESI) method for simultaneous separation and determination of calycosin-7-O-β-D-glucoside, ononin, calycosin and formonometin in Astragali Radix was developed. After the samples were extracted with ethanol, the optimum separation conditions for these analytes were achieved using water and acetonitrile(70:30, v/v) containing 0.2%(v/v) acetic acid as a mobile phase and a 2.0 mm×150 mm Hypersil-Keystone C18 column. Selective ion monitoring(SIM) mode and [M+H]+ ions at m/z 447, 431, 285 and 269 were used for quantitative analysis of four main active components above mentioned. The calibration curves were linear in the range of 0.4-175.0 μg/mL for calycosin-7-O-β-D-glucoside, 0.2-146.0 μg/m L for ononin, 0.4-210.0 μg/mL for calycosin and 0.5-217.0 μg/mL for formonetion, respectively. The limits of quantification(LOQ) and detection(LOD) were 0.4 μg/mL and 0.08 μg/m L for calycosin-7-O-β-D-glucoside, 0.2 μg/mL and 0.06 μg/m L for ononin, 0.4 μg/mL and 0.1 μg/mL for calycosin, 0.5 μg/m L and 0.1 μg/m L formonetion, respectively. The standard recoveries were in the range of 96.5%-104.7%. The developed method has successfully been used for the determination of four main flavonoids in Astragali Radix from various sources and can be used for identification, differentiation and quality evaluation of Astragali Radix.

A Novel Approach for Determining the Orientation of 3-Hydroxyl Group of Some Steroids by CIMS

Trimethylchlorosilane was used as a stereoselective reagent to determine the e or a orientation of 3-hydroxyl group of some steroids by chemical ionization mass spectrometry.

Subsoil Natural Physico-chemical Reactor: The Property of Deep Abiogenic Methane-Containing High-Thermobaric Fluid to Form Coal Seams

For the first time,the property of deep abiogenic methane-containing high-thermobaric fluid to decompose organic residues in the Earth’s crust and form coal seams was established.

Subsoil Natural Physico-Chemical Reactor:Regularity of Natural Processes of Synthesis of Perfect Diamond Crystals

Studies of inclusions(defects)in minerals have shown that the source of carbon in the natural processes of synthesis of perfect diamond crystals is mantle carbon dioxide,(СО2)Р=6.1МPаandδ13С=(-6.1±0.5)‰.A new mechanism for the synthesis of natural crystals of diamond,pyrope,magnetite,quartz,etc.has been developed.It is shown that under the influence of a powerful pulse of tectonogenic energy in some parts of the lithosphere that there are deep faults-tubes,which take root-migrating melt in the direction of the earth’s crust.During migration in the contact zone—“melt-lithosphere rocks”due to their contact interaction-friction,a high-voltage electric field of complex shape is formed,in which CO2 turns into an energy-excited state,its molecules decompose into individual radicals and atoms.In the melt-electrolyte under the influence of an electric field,ions-cations move in certain directions depending on the configuration of the field,which is due to magma,contact with rocks of the lithosphere and the speed of magma in the gap-tube.As they move,these ions undergo numerous collisions with the molecules present there,in particular,СО2 and its atoms and radicals,temporarily forming unstable compounds that fall into the zone with existing iron compounds,etc.OxygenСО2 poatomically detaches from the molecule and forms FeO·Fe2O3(magnetite),and the most energetically advantageous for chemically active carbon atoms in such an environment is that the melt bonds together form a diamond crystal.The isolated SiO2 molecules chemically form a group of garnets,quartz,and the like.

A Convenient Synthesis of 6,8-Dimethoxy-3-[（2-（4-methoxyphenyl）ethyl）isocoumarin

6,8-Dimethoxy-3-[2-（4-methoxyphenyl）ethyl]isocoumarin was synthesized by condensation of 5,7-dimethoxyhompophthalic acid with 3-（4-methoxyphenyl）propanoyl chloride. The structure of the synthesized compound was confirmed by its mass spectrometric studies. The synthesized compound serves as a model for synthesis of DL-agrimonolide.

Application of Spectra Accuracy for Analysis of Organic Explosive: 2,4,6‑trinitrotoluene by AccuTOF‑DART

This paper,through mass spectrometric(MS)analysis for nitro compound explosives on a direct analysis in a real‑time time‑of‑flight MS,indicates that even on a high‑resolution MS with accurate mass measurement capabilities,there is no guarantee to obtain the unique molecular formula of a compound.By calculating spectra accuracy,highly accurate isotope pattern matching can be conducted to significantly improve performance of compound confirmation or identification.