共查询到20条相似文献,搜索用时 15 毫秒
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Novel polysiloxanes, with 4-(dialkylamino)pyridine substituents, are characterized by pyrolysis tandem mass spectrometry. These polymers form abundant cyclic oligomeric ions under both desorption electron ionization (DEI) and desorption chemical ionization (DCI) conditions. Product MS/MS spectra of the cyclic ions reveal characteristic fragmentations under low energy collision activated dissociation. Protonated cyclic oligomers higher than the pentamer are mainly due to the proton bound dimers of lower oligomeric units. The cyclic oligomers are shown to have proton affinities greater than 1000 kJ/mole. It is proposed that thermal depolymerization occurs through an intramolecular siloxane bond rearrangement, which is in agreement with a previously proposed "loop mechanism". Markovian statistical calculations are applied to the DCI mass spectral data in order to determine the sequence distribution of siloxane copolymers. Application of this method show that the monomers in the copolymers examined are non-randomly distributed. 相似文献
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Qiu Tingting Ge Fanliang Li Changhai Lu Shouxiang 《Journal of Thermal Analysis and Calorimetry》2022,147(10):5743-5760
Journal of Thermal Analysis and Calorimetry - The thermal degradation behaviors of commercial flame-retardant unsaturated polyester glass fiber-reinforced plastic (polyester GFRP) containing... 相似文献
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The influence of reprocessing and thermooxidative ageing on the degradation behaviour of a commercial poly(oxymethylene) (POM) copolymer was studied by means of thermogravimetric analysis (TGA) under nitrogen and air atmosphere. Five heating rates were used to evaluate activation energies at several degrees of conversion. TGA-measurements were accompanied by simultaneous monitoring of the evolved gases with a mass spectrometer (MS) coupled to the TGA-furnace outlet. The mass spectra showed that the main degradation product was formaldehyde and that in air further formation of water was detectable. In nitrogen atmosphere aged specimens emitted small amounts of carbon dioxide at the beginning of the mass loss. The activation energy for low degrees of conversion (<5%) increased in air and in nitrogen as a function of the conversion. For higher conversions a difference with progressing degradation emerged: in air, activation energies lowered continuously while they remained nearly constant under nitrogen. 相似文献
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Gembinski C. Charola A. E. Price B. McGhie A. R. 《Journal of Thermal Analysis and Calorimetry》2000,59(1-2):601-609
The combined technique TGA/DTA/MS, thermogravimetric analysis/differential thermal analysis/mass spectrometry, has been used, in conjunction with other analytical techniques, FTIR, SEM, XRD, and optical microscopy, to analyze a specific patching material that had become seriously discolored on its surface after being used to repair a historic stone pillar at Bethesda Terrace in Central Park, New York in the 1980s. The stone patch was found to contain a polyacrylate binder which was associated with the discoloration.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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María Angeles CorresManoli Zubitur Milagros CortazarAgurtzane Múgica 《Journal of Analytical and Applied Pyrolysis》2011,92(2):407-416
The nature and the extent of degradation of poly(hydroxy ether of bisphenol-A) phenoxy resin were analysed by thermogravimetry (TGA/DTGA) under nitrogen and air atmosphere. Decomposition kinetics were elucidated according to Flynn-Wall-Ozawa, Friedman and Kissinger methods. The evolved gases during degradation were inspected by a thermogravimetry analyser coupled with Fourier Transform Infrared Spectrometer (TGA/FTIR) and also with a TGA coupled to a Mass Spectrometer (TGA/MS). Mass spectra showed that chemical species evolved in phenoxy decomposition in air were very similar to those assigned from degradation in nitrogen (water, methane, CO, CO2, phenol, acetone, etc.). However, these species appear in different amount and at different temperatures in both atmospheres. FTIR analysis of the evolved products showed that water and methane were the beginning decomposition products, indicating that decomposition is initiated by dehydration and cleavage of C-CH3 bond in the bisphenol-A unit of phenoxy resin. After this initial stage, random chain scission is the main degradation pathway. Nevertheless, in air atmosphere, previously the complete decomposition of the phenoxy obtaining fundamentally CO2, and water, the formation of an insulated surface layer of crosslinked structures has been proposed. 相似文献
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Kim Seung-Soo Park Sung Hoon Jeon Jong-Ki Chang Daejun Kim Sang Chai Lee Kyong-Hwan Park Young-Kwon 《Research on Chemical Intermediates》2011,37(9):1355-1361
Research on Chemical Intermediates - Pyrolysis Gas Chromatography/Mass Spectroscopy (Py-GC/MS) was used to investigate the catalytic pyrolysis of waste wood chip. Two different mesoporous... 相似文献
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Yiran Liang Lingxiao Wei Cunjin Yang Xiaoping Diao 《International journal of environmental analytical chemistry》2019,99(3):199-208
The dissipation and terminal residues of oryzalin in grape ecosystem under open-field condition were investigated at two different locations, Beijing and Shandong in China. Residues in field-treated samples were determined by a sample method using rapid resolution liquid chromatography triples quadrupole tandem mass spectrometry (RRLC-QqQ-MS/MS). This method showed satisfactory qualitative and quantitative performance. The mean recoveries of oryzalin at different fortification levels (0.01, 0.1 and 1 mg/kg for grape; 0.01, 0.1, 1, 10 and 30 mg/kg for soil) ranged from 88.2% to 98.8%, with the relative standard deviations ≤4.9%. The limits of detection and quantification were, respectively, 0.003 and 0.01 mg/kg. In soil, the dissipation half-lives were about 9 days and the terminal residues ranged from <0.01 to 0.58 mg/kg in both Beijing and Shandong. The concentrations of oryzalin in grapes were lower than 0.01 mg/kg in most of the samples of dissipation study and all the samples of residue study. As far as we know, this is the first study focusing on the dissipation and terminal residue of oryzalin in grape ecosystem, and no maximum residue limits (MRLs) of oryzalin in grapes were recommended by China, Codex Alimentarius Commission or European Union . Therefore, these data not only provide important information about the fate and residues of oryzalin in grape ecosystem, but also could be very useful for the establishment of the MRLs of oryzalin in grapes. 相似文献
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S.P. Marinov L. Gonsalvesh M. Stefanova J. Yperman R. Carleer G. Reggers Y. Yürüm V. Groudeva P. Gadjanov 《Thermochimica Acta》2010,497(1-2):46-51
Thermal analysis, i.e. TGA/DTA is used to study the changes in the combustion behaviour of microbially treated coals. In view of their high sulphur content and industrial significance three samples are under consideration, i.e. one lignite and two subbituminous from different region in Bulgaria. The differences in burning profiles can be related to structural changes resulted from biological treatments. The overall biological treatment generates these changes probably due to the oxidation process. Concerning organic sulphur biodesulphurization there is no change in any drastic manner of the thermal characteristic parameters. In general, applied biotreatments provoke a complex influence on combustion coal behaviour. From one side a better ignition performance, a minor decrease in higher heating value and diminishing peak temperature of maximum weight loss rate for all biotreated samples are observed. From other side some decrease in the combustibility indicated by an increase in the combustion time and the end of combustion temperature are obvious. Also well determined decrease of self-heating temperature after biotreatments evolves high risk of spontaneous unmanageable coal combustion. 相似文献
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The detection of arsenobetaine in extracts of marine algae is reported here for the first time. The application of liquid chromatography coupled online with electrospray tandem mass spectrometry in the selected reaction monitoring mode provided improved performance for the detection of low amounts of arsenobetaine in the presence of high amounts of arsenosugars. 相似文献
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Investigation of pyrolysis of chinese coals using thermal analysis/mass spectrometry 总被引:2,自引:0,他引:2
Li X. Matuschek G. Herrera M. Wang H. Kettrup A. 《Journal of Thermal Analysis and Calorimetry》2003,71(2):601-612
TA/MS (thermal analysis coupled with mass spectrometry) was applied to the pyrolysis of Chinese coals with different ranks.
A total of 13 Chinese coals were investigated. The samples were deliberately chosen to represent the 13 types of Chinese coals
according to the Chinese coal classification system. The experiments were carried out in an argon atmosphere with a flow rate
of 150 ml min-1. The samples were heated from 40 up to 1200°C with a constant heating rate of 10 k min-1. The main evolved pyrolysis products were identified through the on-line recorded mass spectra. The thermal and evolution
behavior was compared between the coals. The results showed a strong thermal and evaluation behavior dependence on the coal
rank. Different aliphatic fragments and also some aromatic substances, which are of environmental concern (BTX, PAHs), were
found to be released depending on the different types of coal.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Influence of pyrolysis temperature and time on the cellulose fast pyrolysis products: Analytical Py-GC/MS study 总被引:4,自引:0,他引:4
Qiang Lu Xiao-chu YangChang-qing Dong Zhi-fei ZhangXu-ming Zhang Xi-feng Zhu 《Journal of Analytical and Applied Pyrolysis》2011,92(2):430-438
Analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was employed to achieve fast pyrolysis of cellulose and on-line analysis of the pyrolysis vapors. Experiments were performed to reveal the effects of pyrolysis temperature and time on the distribution of the pyrolytic products, especially the formation characteristics of eighteen important products. During the fast pyrolysis process, the cellulose started decomposition to form organic volatile products at the set pyrolysis temperature of 400 °C. The pyrolytic products included various anhydrosugars (dominated by the levoglucosan (LG)), anhydrosugar derivatives (mainly the levoglucosenone (LGO), 1,4:3,6-dianhydro-α-d-glucopyranose (DGP), 1,5-anhydro-4-deoxy-d-glycero-hex-1-en-3-ulose (APP) and 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one (LAC)), furan compounds (typically the 5-hydroxymethyl-furfural (HMF), furfural (FF) and furan (F)), as well as light linear carbonyls (mainly the hydroxyacetaldehyde (HAA) and 1-hydroxy-2-propanone (HA)). These products were generated with different characteristics. The LG was the most important product, it was thermally stable, and its formation was favored at elevated pyrolysis temperature and time. Most of the other products were also enhanced at elevated pyrolytic conditions. However, some products, such as the LGO, were favorable to be produced at low temperatures. Based on these characteristics, discussion was performed on the possible pyrolytic pathways for the formation of the important products. 相似文献
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S. Wachholz U. Just F. Keidel H. Gei?ler K. K?ppler 《Fresenius' Journal of Analytical Chemistry》1995,352(5):515-520
On line measurements of infrared and mass spectra of siloxane pyrolysis products separated by gas chromatography are described. The FT-IR absorbance spectra have been recorded from the eluates trapped as small spots on a moving window held at 77 K. Three of the main compounds separated were selected for FT-IR identification performed by comparing the spectra with GC/MS data and by spectral searching using a library of compounds measured under the same conditions.Dedicated to our most honourable teacher Professor Dr. H. Kriegsmann on the occasion of his 70th birthday 相似文献
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《Journal of Analytical and Applied Pyrolysis》2007,78(1):70-75
Pyrolysis–gas chromatography/mass spectrometry was used to compare soil carbon samples from a glacier-retreat chronosequence in the high Arctic. The analysis considered the relative abundance of different pyrolysis products in an attempt to distinguish significant shifts in the soil-C pool. The relative abundance of the compound classes, pyridines, furfurals, phenols, aromatic hydrocarbon precursors, and cyclopentanones were compared. Based on principal component analysis that explained 90% of the variance in the first and second components, the compound classes were well separated. As such, the compound classes selected were well suited for identifying differences among the samples. The most obvious change indicated the appearance of ligninaceous material in the soil-C pool. This shift appeared to occur between 60 and 100 years after glacial retreat. Another less obvious shift was the change from a largely animal dominated early colonization to algae. This shift occurred between 2 and 16 years after glacial retreat. The results suggest that pyrolysis–gas chromatography/mass spectrometry (pyrolysis–GC/MS) can be an effective tool for drawing distinctions between soil-C at different sites and relationship to cover matter. 相似文献
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S. A. Liebman D. H. Ahlstrom C. R. Foltz 《Journal of polymer science. Part A, Polymer chemistry》1978,16(12):3139-3150
This thermal degradation study reports the application of “time-resolved” pyrolysis gas chromatography (PGC) in addition to derivative thermogravimetric analysis (DTGA) to a series of PVC homopolymers with differing branch content and to a model copolymer series with low amounts of propylene in an otherwise vinyl chloride chain. Benzene and toluene generation and decay envelopes were determined during the controlled thermal degradation and related to the derivative TGA experiments. These data allowed interpretation as to the microstructure of the respective polymers and its effect on the degradative pathways. It was concluded that the branch content was not a dominant factor in the initiation of thermal degradation, although it was a factor in other stages of the complex mechanism. A unique fragmentation step was noted only under oxidative thermal exposures, which gave additional support for the theory of low-level unsaturation sites as being significant triggers in the decomposition mechanism. 相似文献
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Vollmer M Hörth P Rozing G Couté Y Grimm R Hochstrasser D Sanchez JC 《Journal of separation science》2006,29(4):499-509
The proteome of the human nucleolus was investigated in a single analysis using off-line strong cation exchange chromatography and microfraction collection combined with HPLC-chip/MS. The analysis was conducted either as a 1-D workflow with HPLC-chip alone or as a 2-D workflow. Two hundred and six unique proteins were identified in the International Protein Index human database corresponding to 2024 unique tryptic peptides identified in the 2-D analysis. In contrast, only 34 proteins and 151 corresponding tryptic peptides were found by applying a 1-D separation strategy. This clearly indicated that the complexity of the samples required the combination of more than one orthogonal separation technique. Stringent database search criteria, including reversal of sequences and therefore better exclusion of false-positive identifications, were applied for reliable protein identification. 相似文献
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Summary From an acetonic extract of the roots ofFerula samarcandica Kor. have been isolated farnesiferol A, gummosin, and two new coumarin substances, samarcandin C24H30–32O5 and samarcandone C24H28–30O5. Samarcandin has been converted into samarcandone and their probable structures-I and II-have been established.Khimiya Prirodnykh Soedinenii, Vol. 4, No. 2, pp. 73–77, 1968 相似文献
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Conclusions It has been shown that the brown algae of the Sea of Japan contain, in addition to alginic acid, acid polysaccharides probably bound to a peptide component.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 2, pp. 73–76, 1969 相似文献
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Seven new diterpenes, featuring the rare 2,6-cyclo-xenicane skeleton, along with eleven previously reported metabolites were isolated from the organic extracts of the brown algae Dilophus fasciola and Dilophus spiralis. The structure elucidation of the isolated natural products was based on detailed analyses of their spectroscopic data (NMR, MS, IR, UV), whereas the assignment of their relative configurations was assisted by molecular modelling studies. 相似文献