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  • Analytical Chemistry and Spectroscopy  (503)
  • Theoretical, Physical and Computational Chemistry  (28)
  • Wiley-Blackwell  (531)
  • 1
    Electronic Resource
    Electronic Resource
    Monitoring the behaviour of 4-ketocyclophosphamide versus cyclophosphamide during capillary gas chromatography by mass spectrometry (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 643-647 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary Gas Chromatography (CGC) is capable of determining underivatized cyclophosphamide (CPA) using SCOT OV 275 columns. Then CPA is subjected to in situ degradation resulting in formation of a cyclization product which can be determined selectively in biological fluids. In routine bioanalysis however cyclization products of CPA metabolites might interfere, e.g. 4-keto CPA. In the present study possible formation of cyclization products of 4-keto CPA similar to CPA was monitored by Mass Spectrometry. Cyclization of 4-keto CPA in situ was demonstrated to occur, resulting in a product similar to that of CPA. Both cyclization products could be determined selectively and it appeared that in situ cyclization of 4-keto CPA was negligible (〈5%), probably owing to extra stabilization of the CPA metabolite by keto-enol tautomerism as has been demonstrated by NMR.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200141113
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  • 2
    Electronic Resource
    Electronic Resource
    A study of some deactivation methods for fused silica capillary columns by CP-MAS NMR and capillary gas chromatography (1985)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 664-672 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Fused silica capillary columns ; CP-MAS NMR ; Deactivation methods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of deactivating a fused silica surface by silylation with 1,1,3,3-tetraphenyl-1,3-dimethylilazane (TPDMDS), triphenylsilylamine (TPSA), and octamethylcyclotetrasiloxane (D4) and by polydimethylsiloxane degradation (PSD) is studied. Rehydrated, dried, and deactivated Cab-O-Sil M5 samples are used as model materials for 29Si CP-MAS NMR analysis.At about 350 °C, TPDMDS yelds mainly diphenylmethylsiloxysilane, dimethyldisiloxysilane, and triphenylsiloxysilane groups. TPSA yields phenyltrisiloxysilane, diphenyldisiloxysilane, and triphenylsiloxysilane groups. At 400°C, the products formed initially are eventually replaced by methyltrisiloxysilane or phenyltrisiloxysilane groups, while a substantial number of silanol groups still remains. The possible consequences for wettability are discussed.D4 reacts with Cab-O-Sil even at 200°C, but a large number of silanol groups remains. This number decreases gradually at higher temperatures and becomes negligible above 400°C. The formation of methyltrisiloxysilane groups, which starts at 425°C, is predominant at 490°C.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240081005
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  • 3
    Electronic Resource
    Electronic Resource
    A CP-MAS NMR study of some deactivation methods in capillary gas chromatography (1984)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 607-614 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Fused silica capillary columns ; CP-MAS NMR ; Silylation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of temperature, water content, and the type of reagent on the silylation of fused silica capillaries was studied by 29Si and 13C CP-MAS NMR. Fumed silica (Cab-O-Sil M5), which is essentially a highly dispersed vitreous quartz with a surface comparable to that of fused silica capillary columns, was selected as a model material.Hexamethyldisilazane (HMDS) and 1,2-diphenyl-1,1,3,3-tetraphenyldisilazane (DPTMDS), which were used as silylation reagents, yielded trimethyl- and dimethylphenylsilyl surface groups respectively at lower temperatures (〈 350°C and 〈250°C respectively). At higher temperatures, increasingly more dimethylsilyl groups are formed, with the silicon bound to two oxygen atoms. This process occurs for DPTMDS at a considerably lower temperature than for HMDS. The formation of silyl groups on the surface and the disappearance of hydroxyl groups are followed independently. The 13C NMR and GC-MS of the reaction products showed that with DPTMDS, the formation of two Si-O-Si links is accompanied by a loss of phenyl groups rather than of methyl groups.After the Cab-O-Sil had been dried over P2O5, the formation of these double links occurred for HMDS only at temperatures above 460°C and for DPTMDS at 400°C. Thus we concluded that water supplies oxygen atoms for double Si-O-Si links (possibly crosslinks) necessary for efficient deactivation. This may explain the less successful silanization of fused silica capillaries because their water content is lower than that of glass capillaries.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240071102
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of oplopanonyl acetate isolated from Chamaecyparis pisifera (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 1030-1034 
    Details
    ISSN: 0749-1581
    Keywords: 2D NMR ; Oplopanonyl acetate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oplopanonyl acetate was isolated from Chamaecyparis pisifera. Its structure and stereochemical features were established using NMR techniques.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260281207
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of pipecolic acid in serum or plasma by solid-phase extraction and isotope dilution mass spectrometry (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 566-571 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of pipecolic acid in serum or plasma by positive chemical ionization gas chromatography/mass spectrometry is assessed. This quantitative method involves stable isotope dilution and cation-exchange solid-phase extraction. Several derivatives of pipecolic acid and its octadeuterated analogue were investigated for their mass spectrometric characteristics. The beptafluorobutyric methyl ester derivatives afford optimal resolution on gas chromatography of biological extracts. Moreover, the derivatizing reagent (methanolic HCl) allows a combined elution and derivatization. Selected ion monitoring is performed on the [M + H]+ ions of both analyte and internal standard, at m/z 340 and 348, respectively. Serum or plasma samples from healthy subjects and patients suspected of peroxisomal diseases have been examined.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180810
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of gases on the native fluorescence of some butyrophenones on thin-layer plates (1980)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 423-424 
    Details
    ISSN: 0935-6304
    Keywords: High performance thin-layer chromatography (HPTLC) ; Butyrophenones ; Fluorescence ; Flushing gases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240030812
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  • 7
    Electronic Resource
    Electronic Resource
    Correlations between HPLC and NMR properties of some selected alkyl bonded phases (1983)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 6 (1983), S. 433-435 
    Details
    ISSN: 0935-6304
    Keywords: Reversed-phase HPLC ; Solid state NMR ; Surface characterization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240060806
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  • 8
    Electronic Resource
    Electronic Resource
    Gas chromatographic determination of residual ethylene oxide in gas-sterilized, medical-grade plastics (1984)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 587-589 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Packed glass columns ; Solvent extraction ; Plastics ; Ethylene oxide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240071011
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  • 9
    Electronic Resource
    Electronic Resource
    CPtmWax 57 CB: A chemically bonded polyethylene glycol stationary phase for gas chromatography (1982)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 5 (1982), S. 501-503 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, fused silica ; Chemical bonding - cross-linking ; Polar columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240050910
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  • 10
    Electronic Resource
    Electronic Resource
    Deactivation with silazanes in chromatography, mechanism of the reaction and practical consequences in capillary GC and RP-HPLC: A29Si CP-MAS NMR study (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 741-746 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; RP-HPLC ; CP-MAS NMR ; Deactivation methods ; Hexamethyldisilazane ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of Cab-O-Sil, a highly dispersed vitreous quartz, with hexamethyldisilazane (HMDS) was studied in the temperature range 380-500°C, using 29Si solid state NMR and other techniques. Such studies are of importance in view of deactivation procedures of fused silica at high temperatures in capillary GC.The commonly accepted reaction equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ \left({{\rm Me}_{\rm 3} {\rm Si}} \right)_2 {\rm NH } + {\rm 2}\equiv {\rm SiOH} \to {\rm 2} \equiv {\rm SiOSiMe}_{\rm 2} + {\rm NH}_{\rm 3} $$\end{document} predominates only below ca. 400°C. Above ca. 400°C the intermediate cleavage product Me3SiNH2 reacts with surface silanol groups to form ≡SioSiMe2NH2 + CH4. At higher temperatures these groups may ultimately form (≡SiO)3SiNH2 groups (analogously to the formation of bi-and tridentate linkages starting from ≡SiOSiMe3 groups), but (≡SiO)3SiNH2 groups are also directly formed at lower temperatures, simultaneously with the ≡SiOSiMe3 groups, probably by reaction with siloxane bridges: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Me}_3 {\rm SiNH}_2 + \equiv {\rm SiOSi} \equiv\; \to \;\equiv SiNH_2 + \equiv SiOSiMe_3 $$\end{document}.The reactions of the trimethylsilylamine part of HMDS with Cab-O-Sil were confirmed by an independent series of silylations using N,N-dimethyltrimethylsilylamine instead of HDMS. The presence of amino groups as ≡SiNH2 was confirmed by FT-IR. This may be one of the reasons why very high temperature silylation with disilazanes does not provide a satisfactory deactivation of fused silica GC columns: the active ≡SiOH groups are “replaced” by active ≡SiNH2 groups. However, such a material may be of interest in LC. Silylation with silazanes at ca. 350°C in humid atmosphere and/or after extensive hydroxylation (leaching) of the surface should yield sufficiently deactivated surfaces with a rather well defined surface structure.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240091206
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