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  • 1
    Electronic Resource
    Electronic Resource
    Direct observation of morphological differences as a function of reaction temperature in model systems for polyurethane foams (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 3065-3077 
    Details
    ISSN: 0887-6266
    Keywords: polyurethanes ; AFM ; atomic force microscopy ; phase separation ; crosslinking ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of polyurea urethanes was isothermally synthesized from toluene diisocyanate (TDI), water, and trifunctional poly(propylene oxide) in the temperature range of 50-150°C. Morphologies of the samples vary significantly as a function of reaction temperature. In this system, phase separation competes with polymerization and crosslinking. Both transmission electron microscopy and atomic force microscopy have shown a network type of structure for the 50°C samples, while the 150°C samples appear to be homogeneous. Infrared analysis shows that samples prepared at 150°C possess a morphology that is less strongly hydrogen bonded and has a broader distribution of hydrogen-bonded states compared to those prepared at lower temperatures. From this combination of techniques, it can be inferred that phase separation occurs faster than crosslinking at low temperatures; consequently, a phase-separated morphology forms. In contrast, crosslinking occurs faster than phase separation at higher reaction temperatures. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3065-3077, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Comparison of radioimmunoassay and gas chromatographic mass spectrometric assay for d-amphetamine (1979)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1979), S. 187-190 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quantification of low levels of psychotropic drugs (10-7 to 10-9 g ml-1) in small volumes of plasma requires sensitive and accurate methods. Validation of these methods is best achieved by comparing results obtained using several techniques. In this study, amphetamine levels in plasma were measured using gas chromatography mass spectrometry and radioimmunoassay. Correlation of the results obtained by the two methods was found to be positive and high (R = 0.9822). The average coefficient of variation between assays for gas chromatography mass spectrometry was 5.8% and for radioimmunoassay was 12.3%, while the average coefficient of variation within assays for gas chromatography mass spectrometry was 4.9% and for radioimmunoassay 6.9%. Although gas chromatography mass spectrometry was 1.9 times more sensitive than radioimmunoassay, for most purposes, the convenience of the radioimmunoassay method outweighs the technical superiority of gas chromatography mass spectrometry.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200060503
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of monomers and copolymers from isatoic anhydrides (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 2679-2681 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.170161024
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  • 4
    Electronic Resource
    Electronic Resource
    Quasi-equilibrium states of copolymers that simultaneously crystallize and interchange structural units (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 2651-2661 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quasi-equilibrium model of a step-growth copolymer that crystallizes and interchanges structural units simultaneously is presented. Equilibrium values of counit-sequence-length distribution in the amorphous phase and degree of crystallinity are calculated in a system for which crystallite thickness is determined by nucleation. When applied to calculations, the model predicts that the counits of the amorphous phase will tend to be ordered in blocks. The crystalline content of the whole polymer and the extent of ordering counits along the chain decreases with increasing temperature. The model predicts temperature ranges for some whole copolymers in which one of two similarly stable, disparate combinations of crystallinity and sequence-length distribution may prevail.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.170161019
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  • 5
    Electronic Resource
    Electronic Resource
    Statistical approaches to the copolymerization equation and the steady-state assumption (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 633-634 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.170210232
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  • 6
    Electronic Resource
    Electronic Resource
    Metabolism of 1,1,1,2,2-pentafluorohexane and 1,1-difluorocyclohexane by rat liver microsomes in vitro (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 512-521 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metabolism of 1,1,1,2,2-pentafluorohexane with liver microsomes from phenobarbital-treated rats gave only one metabolite, namely, the 5-hydroxy derivative. Under similar conditions 1,1-difluorocyclohexane was metabolized to give mainly the 3- and 4-hydroxy derivatives in the ratio 1:∼5.5 The structures of these metabolites were established by chemical ionization (CI) and/or electron impact (EI) mass spectrometry and confirmed by synthesis in the case of 1,1-difluorocyclohexan-4-ol. Oxidation of 1,1-difluorocyclohexane with lead tetrakis(trifluoroacetate) also gave, inter alia, the 3- and 4-hydroxy derivatives. In saturated hydrocarbons complete replacement of hydrogen by fluorine at one particular carbon will not only block microsomal hydroxylation thereat but will also inhibit hydroxylation at neighbouring hydrogen-bearing carbons, (α almost completely, β markedly, γ slightly).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200111005
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of prior crystallinity on the flow-induced crystallization of poly(ethylene oxide) (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 1097-1113 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: After flowing in a dilatometer bulb for a small fraction of the duration of the transformation, a relaxed melt of poly(ethylene oxide) (M̄n = (5.9 ± 0.1) × 103) showed marked increases in isothermal crystallization rate. The extent of increase was greater when flow was imposed at modestly later stages rather than at the earliest stage of a crystallization. Kinetic parameters for the flow-induced crystallizations were obtained via modification of the conventional mathematical treatment of the kinetics of phase change, thereby allowing the analytical resolution of the overall process into flowinduced and quiescent components. Determination of the flow-induced crystallization parameters required independent determination of the kinetic parameters for quiescent crystallizations at that temperature. The Avrami exponents nf which characterized the flow-induced portions of the crystallizations were larger for those instances in which flow was imposed at the more advanced stages of the crystallizations, thus indicating a transition in crystallization mechanism. It is suggested that prior crystallinity present at the time of flow contributed to the crystallization by serving as a source of nucleation sites. However, in light of the experimental procedure employed, values of nf approximating 4 that were obtained are not susceptible to mechanistic interpretations now extant.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.180130604
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  • 8
    Electronic Resource
    Electronic Resource
    Octafluorotoluene as a derivatizing agent for steroids in human plasma (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 211-213 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of octafluorotoluene (OFT) as a versatile gas chromatographic/mass spectrometric derivatizing agent for steroids containing alcoholic, phenolic or α,β-unsaturated keto functions, is described. Two distinct derivatizing schemes can be utilized, involving (method 1) a phase-transfer reaction, employing a two-phase system of CH2Cl2 and N NaOH with n-Bu4NHSO4 as catalyst (suitable for alcoholic and phenolic steroids) and (method 2) a reaction conducted in anhydrous dimethylformamide at 155°C with CsF as base (appropriate for α,β-unsaturated keto steroids). Perfluorotolyl (PFT) ethers and/or enol ethers have thus been generated. The electron impact spectra display abundant high-mass molecular ions where derivatization has occurred at a phenolic or enolic function. An extraction, derivatization and gas chromatographic/mass spectrometric scheme has been devised involving method 2 for the analysis of steroids in human plasma. A preliminary quantitative investigation of the levels of testosterone in plasma has been carried out employing these methods. The anomalously high level found is explained in terms of the presence in plasma of lipid-soluble derivatives of testosterone (probably fatty acid esters) which generate the testosterone bis-OFT derivative under the reaction conditions employed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160138
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  • 9
    Electronic Resource
    Electronic Resource
    Confirmation of oxytetracycline, tetracycline and chlortetracycline residues in milk by particle beam liquid chromatography/mass spectrometryThis work was presented in part at the 38th ASMS Conference on Mass Spectrometry and Allied Topics, Tucson, Arizona, June 1990. (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1991), S. 789-795 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method using particle beam liquid chromatography/mass spectrometry was developed for the confirmation of oxytetracycline, tetracycline and chlortetracycline residues in bovine milk. This method is one of the first to apply particle beam technology to the confirmation of animal drug residues in food products for regulatory purposes. The milk is centrifuged, using molecular weight cut-off filters to remove components of 25 000 daltons and above from the milk. The filtrate is passed through a C-18 sample preparation cartridge which retains the tetracyclines. After the columns are washed with water, the tetracyclines are eluted with 0.1 M oxalic acid in methanol and concentrated. The compounds are separated on a Novapak C-18 column with a methanol-oxalic acid-acetonitrile mobile phase. Negative chemical ionization with selective ion monitoring is used to identify the tetracyclines. The procedure was used to confirm the presence of each tetracycline at 100 ng ml-1 in fortified and incurred milk samples.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200201208
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis of mercapturic acid conjugates of xenobiotic compounds using negative ionization and tandem mass spectrometryPresented in part at the 36th Annual Conference on Mass Spectrometry and Allied Topics, San Francisco, 1988. (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1993), S. 68-76 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of mercapturic acid conjugates of two xenobiotic products of lipid peroxidation (trans-4-hydroxy-2-hexenal and trans-4-hydroxy-2-nonenal) as well as conjugates of 1,3-dichloropropene, styrene oxide, 1,2-naphthalene oxide and α-chlorotoluene were obtained using fast atom bombardment or negative chemical ionization. Fragmentation pathways were investigated using linked scan and mass-analyzed ion kinetic energy spectrometric techniques. Characteristics of the spectra obtained using different ionization and sample introduction techniques are compared. Deprotonated molecular ions of mercapturic acids gave simple daughter ion spectra, with the dominant mode of decomposition involving cleavage of C—S bonds giving a characteristic neutral loss of 129 Da Screening for mercapturates in urine samples was performed using neutral loss scanning and yielded limits of detection in the low nanogram per milliliter range. Quantitative analysis of the S-benzyl mercapturic acid at 1 p.p.b. in urine has been demonstrated using combined gas chromatography/electron capture mass spectrometry with d3-S-benzyl mercapturic acid as internal standard.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200220109
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