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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 174-176 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma levels and urinary excretion of mevalonate were reported to be correlated with cholesterol biosynthesis. Evaluation of mevalonate concentration in plasma and urine represents therefore a non-invasive method for studying the modifications of cholesterol synthesis. A method is described here by wich mevalonate in plasma and urine is determined by the selected ion monitoring technique after extraction as mevalonolactone and conversion into the trimethylsilyl ether. Linear responses were obtained in the evaluation of mevalonate added to plasma in the 10-100 ng/ml (r 〉 0.995) and to urine in the 50-1000 ng/ml concentration ranges, respectively. Identity of mevalonate in plasma and urine was confirmed by high-resolution mass spectrometry.
    Additional Material: 2 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1991), S. 40-40 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1994), S. 514-518 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrolysis of cyclosporin A (CsA) was studied in order to clarify the still undefined point of attack of the acidic degradation. Among ether extractable and water-soluble products formed from CsA in HCl, two open-chain peptides were isolated by high-performance liquid chromatography which were identified as the deca- and nonapeptides deriving from CsA through the hydrolytic cleavage of amino acid residue 11 and both residues 11 and 10, respectively. Identification was carried out by fast atom bombardment tandem mass spectrometry.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1991), S. 426-430 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple and rapid gas chromatographic/mass spectrometric method to determine plasma diclofenac was developed, which employs formation of the methyl ester with diazomethane. Methoxydiclofenac was used as the internal standard. Under the conditions used, the previously described partial cyclization of diclofenac to the indolone derivative was avoided. The limit of detection of plasma levels of diclofenac is 2 ng ml-1, which renders the method useful for clinical studies on oral, intravenous and rectal administration of the drug. The analysis is carried out by electron impact gas chromatography/mass spectrometry and can therefore be performed on the more common mass spectrometers. Linearity and reproducibility of the method were demonstrated by the high correlation coefficient of the calibration lines (r 〉 0.999) and from the low variation of their slopes (coefficient of variation 3%) determined on different days, respectively. Pharmacokinetic parameters (area under curve = 1.8 ± 0.26 μg h ml-1, tmax = 1.5 ± 0.5 h, Cmax = 734 ± 82 ng ml-1 and terminal half-life = 0.88 ± 0.52 h) determined from the plasma decay of diclofenac in three healthy subjects given a single oral dose of diclofenac were in good agreement with those reported in the literature.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1994), S. 173-173 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 366-370 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Sampling problems by syringe needle temperature ; Technical solution of the problems by cooling and heating up minimized masses ; Discrimination and standard deviation measured with test mixtures C18-C38 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On-column injection into a hot gas chromatograph oven involves the danger that the bottom part of the needle is warmed up above the boiling point of the solvent in the sample. Consequently parts of the sample are evaporated out of the needle instead of being introduced as a liquid into the capillary column. This causes losses and hence discrimination of the less volatile parts of the sample which remain in the needle.A technical solution is proposed using a system for cooling the capillary during the injection, down to the injection point in the oven.
    Additional Material: 2 Ill.
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  • 7
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns ; Simulated distillation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The characterization of heavy petroleum fractions is essential for the design and improvement of cracking plants converting heavy feedstock into valuable “white” products. Conventional simulated distillation methods using packed columns are unsuitable for this purposes, being limited to boiling points up to about 600°C. The method presented is able to cover a boiling points interval ranging from about 150°C up to around 800°C. It employs a short, nonpolar, highly thermostable capillary column routinely operated at temperatures around 430°C. The analytical system is based on a high temperature versions of a fully automatic, capillary dedicated gas chromatograph. The experimental data demonstrate that cold on-column injection is the sole sampling system suitable for such heavy compounds. The conversion of the retention times into boiling points, based on the use of low molecular weight polyethylenes, is extremely reliable, as demonstrated by the excellent retention time reproducibilities. The lower part (up to 550-600°C TBP) of the boiling point distribution curves of heavy petroleum fractions obtained on capillary columns fits well with the corresponding distribution curves based on packed column data. For the petroleum fractions fully eluted from the column the quantitative results obtained either using internal standards or by direct processing of the elution curves are in excellent agreement (less than 0.3 weight% differences). The method has been applied to the determination of the true boiling points corresponding to short path vacuum distillation (DISTACT) cut points over 300°C.
    Additional Material: 18 Ill.
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  • 8
    ISSN: 1040-7685
    Keywords: Enantioselective GC ; 2,3-di-O-acetyl-6-O-t-butyldimethylsilyl-β-cyclodextrin ; diluting stationary phases (PS-086, OV-1701) ; retention parameters ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results of a series of experiments concerning the GC enantioseparation of some racemates on columns coated with 2,3-di-O-acetyl-6-O-t-butyldimethylsilyl-β-cyclodextrin diluted in two different polysiloxanes (PS-086 and OV-1701) are reported. The investigation is centered on the influence of the diluting phase on the separations of the racemates investigated [δ-heptalactone, linalyl acetate, and an homologous series of cis-2-(2-alkyl-cyclopropyl)-ethanol (alkyl from ethyl to heptyl)] because one of the two polysiloxanes separated them, whereas the other did not. Column retention and efficiency characteristics were investigated as a function of the diluting phase. Retention increase (RI) and Gibbs-Helmholtz parameter (ΔR,SΔG) were determined for each of the above racemates, analyzed by different mixtures of the CDD selector with the two diluting phases. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 484-486 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Capillary columns ; Polyolefins ; Antioxidants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 349-352 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Press-fit connectors ; Y connectors ; On-column/dual column ; Multidetection ; Essential oils ; 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
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