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  • Analytical Chemistry and Spectroscopy  (109)
  • Engineering  (15)
  • Theoretical, Physical and Computational Chemistry
  • Wiley-Blackwell  (124)
  • 1985-1989  (124)
  • 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
    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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  • 4
    Electronic Resource
    Electronic Resource
    PoraPLOT Q: A porous layer open tubular column coated with styrene-divinylbenzene copolymer (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 162-167 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns ; PLOT columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A porous polymer is deposited on the inner wall of fused silica capillary columns. The retention characteristics of this porous polymer were evaluated and found to be comparable with Porapak Q. The porous polymer has a high retention volume which enables the separation of permanent gases at ambient temperatures or higher. The hydrophobic character of the porous polymer allows the injection of water containing samples without changing retention due to adsorption of water. The inertness of the porous polymer allows the elution of a range of apolar and polar compounds. The maximum temperature of the porous polymer was estimated to be 250°C. With this new type of capillary column, high resolution separations are obtained in combination with short analysis times.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110204
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  • 5
    Electronic Resource
    Electronic Resource
    Deactivation by polysiloxane and phenyl containing disilazane: A 29SI CP-MAS NMR study after the formation of polysiloxane chains at the surface (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 510-516 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; Deactivation ; 29Si-NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A high degree of deactivation of glass and fused-silica capillary column walls is attainable by means of high temperature silylation (HTS) with or without a preceding leaching process. HTS with a phenyl containing disilazane, diphenyltetramethyldisilazane (DPTMDS), and polydimethylsiloxane (PDMS) are studied on Cab-O-Sil, a fumed silica, as a model substrate. Using 29Si CP-MAS NMR, it was shown that no dimethylsiloxane chains were formed upon silylation with DPTMDS under different conditions of humidity and stoichiometry at 377°C. With DPTMDS deactivation it is possible that amino trisiloxy silane groups are formed, these groups add extra activity to the surface. Silylation with a PDMS, OV 101, at various temperatures between 300°-420°C did show that dimethylsiloxane chains were bonded at the surface. Using the 29Si CP-MAS NMR technique with variable contact times to reveal siloxy group mobility, the degradation of dimethylsiloxane chains at the surface was studied. PDMS degradation at an optimal temperature gives a more effective diminuation of the silane activity caused by chemical reaction with the silanol groups and the effective screening of the remaining silanol groups with anchored polydimethylsiloxane chains and small cyclodimethylsiloxane ring structures at the surface.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110703
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    HPLC determination of valproic acid in human plasma by derivatization with O-p-nitrobenzyl-N,N′-diisopropylisourea (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 540-543 
    Details
    ISSN: 0935-6304
    Keywords: High performance liquid chromatography, HPLC ; Adsorption HPLC system ; Partition reverse phase HPLC system ; Valproic acid, VPA ; Antiepileptic drugs, AEDs ; O-p-Nitrobenzil-N,N′-diisopropylisourea, PNBDI ; Enzyme immunoassay, EMIT ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sensitive and specific method for the determination of valproic acid in plasma has been developed. After the proteins in the plasma have been precipitated with a saturated solution of ammonium sulfate in 1N HCl, the valproic acid, together with the internal standard, is extracted from the plasma with dichloromethane.An aliquot of the organic solution is taken for derivatization of the valproic acid and the internal standard with O-p-nitrobenzyl-N,N′-diisopropylisourea.Separation is carried out by HPLC using two chromatographic systems: an adsorption system with a μ Porasil column, hexane-chloroform (94:6) as mobile phase, and caproic acid as internal standard and a partition reverse phase system comprising a μ Bondapak TM/C18 column, acetonitrile/methanol/0.0035 M phosphate buffer (60:10:30), and caprylic acid as internal standard. UV detection is at 254 nm.This method, developed in both systems, permits the determination of plasma levels of valproic acid in the reported range of 50-100 μg/mL. With adequate sensitivity, specificity, precision, and accuracy.The plasma levels of valproic acid may be determined by this method without interference from the commonest antiepileptic drugs. Good correlation is obtained with the enzymatic immune analytic method: EMIT.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240120809
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of volatile amines in drug substances by capillary gas chromatography (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 604-607 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Two-phase acylation ; Aziridine ; 2-Chloroethylamine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of small, water soluble amines such as aziridine and 2-chloroethylamine, in drug substances at trace levels is described. After removal of the bulk of the drug substance by extraction or precipitation, derivatization with acid chlorides is performed. In a two-phase (water-organic solvent) system, this derivatization reaction is accomplished almost simultaneously with the extraction of the product to the organic layer. The organic layer is analyzed by gas chromatography using on-column injection and selective detection. Detection limits are approx. 0.2 mg/kg for aziridine and approx. 0.5 mg/kg for 2-chloroethylamine.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240120906
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  • 9
    Electronic Resource
    Electronic Resource
    Measurement of propericiazine in plasma by capillary gas chromatography and selected ion monitoring detection (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 25-29 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method, based upon a selective extraction and gas chromatographic/mass spectrometric analysis, was developed to monitor the effect of combined haemoperfusion-haemodialysis treatment in a case of propericiazine poisoning. The method relies on the selected ion monitoring of the acetate derivatives of propericiazine and its internal standard fluphenazine, after their extraction from 1 ml of alkalinized plasma with n-hexane: isopropanol (8:2, v/v), back-extraction into an acidified water phase, realkalinization and extraction with n-hexane:isopropanol, derivatization with acetic anhydride and gas chromatography on a short (12 m) OV-101 fused silica capillary column. The described procedure is specific and provides between-assay variability of 4.8% CV at 5 μg I-1 plasma concentration. The method enables quantification down to 1 μg I-1 and hence demonstrates sufficient sensitivity to permit pharmacokinetic or drug monitoring studies.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200120106
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  • 10
    Electronic Resource
    Electronic Resource
    The problems of oral contraceptives in dope control of anabolic steroids (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1988), S. 127-128 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200170209
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