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  • 1
    Electronic Resource
    Electronic Resource
    Influence of agricultural soil management on humus composition and dynamics: Classical and modern analytical techniques (1992)
    Springer
    Plant and soil 142 (1992), S. 259-271 
    Details
    ISSN: 1573-5036
    Keywords: chemometric evaluation ; crop rotation ; pyrolysis-mass spectrometry ; soil management ; soil organic matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In-source pyrolysis-field ionization mass spectrometry (Py-FIMS), in combination with complementary elemental, wet-chemical, biochemical, and microbiological data, has been used to characterize humus composition and dynamics in soil samples from several field plots that have been cultivated in long-term experiments under different management conditions. Thermograms and Py-FI mass spectra of whole-soil samples from field plots that under very different management show significant differences in humus composition, which may be due to varying stages of decomposition of plant residues and humus genesis. The intensity of soil management significantly affects high-molecular-weight subunits such as dimeric lignin0, arylalkyl-, and aliphatic constituents, even though humus quantity is similar for plots under more practically oriented management, such as crop rotation. The differences in molecular humus subunits of soil samples from different plots, in combination with complementary data, demonstrated that less parent (i.e. primary) material is incorporated in the humus matrix under intense soil management conditions. Samples from different field plots can thus be objectively differentiated on the basis of humus properties using multivariate statistical techniques such as principal component and cluster analyses. This statistical discrimination, using Py-FI mass spectra of the samples, corresponds well with microbial biomasses but is somewhat inconsistent with elemental data and results of chemical degradation procedures. The microflora populations in soils under intense management are limited by low availability and/or quality of carbon substrates. The resulting restricted internal nitrogen cycle causes those soils to have a reduced capacity to immobilize N, leading to relative enrichment of heterocyclic nitrogen compounds that are resistant to mineralization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010971
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization and chemodynamics of plant constituents during maturation, senescence and humus genesis in spruce ecosystems (1991)
    Springer
    Biogeochemistry 13 (1991), S. 27-60 
    Details
    ISSN: 1573-515X
    Keywords: chemical characterization ; chemodynamics ; conifer ecosystem ; humus genesis ; maturation ; pattern recognition ; plant constituents ; pyrolysis-mass spectrometry ; senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Spruce needles of different age, litter materials and soil samples from the L-, O-and A-horizons of a mor profile were analysed by temperature-programmed pyrolysis (Py) in combination with field ionization mass spectrometry (FIMS). The integrated Py-FI mass spectra give characteristic fingerprints of the biomaterials investigated. The application of principal component analysis to the mass spectral data results in a clear discrimination and classification of the samples reflecting the chemical modifications and transformations of organic matter by biochemical and biogeochemical processes. The chemical compositions are determined by processes such as enrichment and/or translocation of plant constituents (e.g. carbohydrates, lignin, lipids, suberin, and aliphatic polymers) during maturation and senescence of needles; amendment of new components; decomposition; selective preservation and humification processes in the soil environment. During needle maturation, major chemical changes include the decrease of carbohydrate content, condensation of lignin, and crosslinking of waxes. Senescent needles are characterized by lower contents of carbohydrates and lower yields of monomeric pyrolysis products from lignin. The contribution of different litter materials to the humus layer can be estimated by differences in chemical composition. During litter decomposition and humification on the forest floor, carbohydrate content decreases rapidly. The lignin content remains almost constant but some subunits are continuously oxidized. Wax material accumulates until the mechnical disintegration of the needle occurs. In the O-horizons polymeric aliphatic materials are enriched in humified plant remains. A constant increase of aryl-alkyl esters from suberin in the O-horizons is due to both root input and selective preservation. In general, mainly aliphatic polymers and aryl-alkyl esters accumulate during the genesis of mor profiles under conifers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002875
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal reactions of amphotropic copolymers studied by thermogravimetry and temperature-resolved pyrolysis-field ionization mass spectrometryDedicated to Prof. Dr. H. D. Beckey on the occasion of his 70th birthday (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1567-1587 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal degradation mechanisms of amphiphilic acrylic copolymers containing mesogenic pyrimidine side chains and hydrophilic 2-hydroxyethyl acrylate (HEA) main-chain spacer units were investigated by thermogravimetry (TG) and pyrolysis-field ionization mass spectrometry (Py-FIMS). The degradation behaviour of these polymers depends on the amount of HEA incorporated. Thermogravimetry revealed that the main decomposition occurs in a single step for the pyrimidine homopolymer, whereas with increasing HEA content a two-step process evolves. The major products identified by Py-FIMS are two alcohols and one olefin split from the aromatic side chains. Depolymerization is only a minor degradation pathway. The rather complex thermal behaviour can be explained by three different reaction mechanisms: (a) alcohol formation via reaction of the HEA hydroxyl groups with ester groups in the side chains, (b) intramolecular cis-elimination forming a volatile olefin and carboxylic acid groups remaining at the polymer backbone, and (c) the reaction of these acid groups with ester bonds forming the alcohols. Steps (b) and (c) are dominant for the pyrimidine homopolymer. With increasing HEA content in the copolymers step (a) becomes more important and, in addition, chemical crosslinking occurs. The mesogenic monomer, which was also examined, polymerized under the experimental conditions and showed essentially the thermal features of the pyrimidine homopolymer.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920711
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal degradation of aliphatic polyamides studied by field ionization and field desorption mass spectrometry (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 2381-2394 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aliphatic polyamides nylon 6.6, 6.9, 6.10, 6.12, 12.6, 12.10, and 12.12 of the diamine dicarboxylic acid-type were pyrolyzed in the ion source of a double-focusing mass spectrometer and the thermal degradation products were recorded by field ionization (FI) and field desorption (FD) mass spectrometry (MS). In the FI mode, several series of thermal degradation products differing in the number of polymer repeating units were detected up to 1000 Daltons. The main products were oligomers and, in addition, protonated dinitriles and various protonated nitriles are formed in large amounts except for nylon 6.6 and nylon 12.6. These two polymers form, in contrast to all other samples, large amounts of protonated amides and diamines. The technique employed allows distinction between oligomers already present in the original polymer and oligomers formed by thermal fission of bonds in the polymer chain. Reaction mechanisms are given that explain the products observed. High resolution experiments and accurate mass measurements were performed to confirm the proposed structures. In the FD mode, cationized oligomers (attached mostly to a sodium cation) were observed below 200°C with the dimers being the base peak for most samples. In contrast to the FI results, the monomers were only detected at very low intensities. Similarly, only weak signals for additional thermal degradation products were registered except for nylon 12.6. At higher temperatures the FD mass spectra gave protonated and doubly protonated oligomers in the high mass range up to 2000 Daltons, which resulted in complementary structural information about the polymers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080260911
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  • 5
    Electronic Resource
    Electronic Resource
    Pyrolysis-gas chromatography mass spectrometry and field ionization mass spectrometry of polyquinones (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 1027-1043 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low- and high-molecular mass thermal decomposition products of five polyquinones with different linking aromatic structures have been analyzed by pyrolysis-gas chromatography and by direct (in-source) pyrolysis-field ionization mass spectrometry. The quantity of carboxyl groups present in the polymer is obtained by the amounts of carbon dioxide found by pyrolysis-gas chromatography. Assuming a radical thermal decomposition mechanism the distribution of ketoacidic and quinonoid segments along the macromolecular ladder could be estimated from the high-molecular mass products measured by pyrolysis-field ionization mass spectrometry. A random distribution of the two different segments was found for polyquinones with biphenylene and dibenzofuran subunits, while a structure built up of blocks of two or more identical segments was obtained for polyquinones with dibenzothiophene and diphenylmethane subunits. At the same time the anomalous structural moieties in the polyquinone ladders are also clarified with the help of the identification of the unexpected pyroysis products. Oxidated and bis-dibenzothiophene and bis-diphenylmethane subunits were found. The observed temperature dependence for the appearances of the thermal degradation products indicates that condensation and elimination reactions are taking place under the described pyrolysis conditions. Condensation in the ketoacidic segments forming new quinonoid segments proved to be important in the polymer which was a 100% poly(ketoacid), but negligible in the polyquinones containing ketoacidic segments up to 60%.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270325
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  • 6
    Electronic Resource
    Electronic Resource
    Pyrolysis-field ionization mass spectrometry of polyamide copolymers and blends (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 123-134 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Nylon foils of PA 6, PA 66, PA 69, PA 12, the copolymer PA 666, and nine blends based on these polymides have been investigated by in-source pyrolysis (Py)-field ionization mass spectrometry (FIMS). These polymers and blends can be distinguished by characteristic molecular ions of oligomers, protonated amines and nitriles, and products terminated by olefinic end groups. Series of ions are formed differing in the number of additional monomeric units. Thus, polymers containing different chemical subunits were easily distinguished from each other in the spectra of the blends. Mass signals, only expected for copolymers, were found in the integrated blend spectra, indicating that amide exchange reactions occur under the experimental conditions employed. This observation was confirmed by pyrolysis of mixtures of pure polymers in the same crucible and under the same experimental conditions. Hence, the distinction by Py-MS alone between blends and copolymers with an identical averaged number of identical chemical subunits is not possible.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070380112
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