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  • 1990-1994  (7)
  • Life Sciences (general)  (4)
  • Biochemistry and Biotechnology  (2)
  • Analytical Chemistry and Spectroscopy  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 34-39 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Cold trapping ; Sampling in stainless steel canisters ; Calibration ; Halocarbons in remote areas ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 5 ml air samples from 1.6 l stainless steel canisters were cryogenically preconcentrated before gas chromatographic separation on a thick-film capillary using a home-made cryotrap. Quantification in the 10-500 ppt range was carried out with an electron capture detector. Problems during the cryotrap step were caused by carrier gas contamination, water and CO2 content of the sample, and a non-optimal heat desorption rate. Their elimination is described in detail. Compound losses by wall adsorption on stainless steel surfaces were observed when dry gases were used for standard generation. A static multipoint calibration technique using humidified He was developed allowing a precise standard generation down to 100 ppt. The concentration changes in the stainless steel canisters could be neglected over a storage period of at least 1 month as long as a sufficient degree of humidity was present. The overall reproducibility of the quantification and calibration technique is in the order of 1-2% for concentrations between 100-400 ppt when daily recalibrations are carried out.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 8 (1993), S. 307-313 
    ISSN: 0884-3996
    Keywords: Luminol ; sodium hypochlorite ; hydrogen peroxide ; inhibition of chemiluminescence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Two different mechanisms of inhibition of chemiluminescence in the oxidation of luminol by sodium hypochlorite were found. Most substances investigated in these experiments acted by scavenging NaOCI. This mechanism was independent of the concentration of hydrogen peroxide and the incubation time between luminol and inhibitors. The most potent inhibitors were substances containing SH groups. Compounds with amino groups as a target for HOCI/OCI- to yield chloramines were much less effective inhibitors. Another mechanism of inhibition was found for catalase. It depended on the presence of hydrogen peroxide in the incubation medium and the incubation time between luminol and catalase. The enzyme inhibited the luminescence by removing H2O2 at molar concentrations much smaller than those found for all other inhibitors. Our results confirm the present models of the mechanism of generation of luminescence in luminol oxidation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 6 (1991), S. 189-192 
    ISSN: 0884-3996
    Keywords: Luminol ; sodium hyochlorite ; hydrogen peroxide ; chemiluminescence intensities ; chemiluminescence spectra ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Hydrogen peroxide amplifies the chemiluminescence in the oxidation of luminol by sodium hypochlorite. A linear relationship between concentration of hydrogen peroxide and light intensity was found in the concentration range 5 × 10-8-7.5 × 10-6 mol/l. At 7.5 × 10-6 mol/l H2O2 the chemiluminescence is amplified 550 - fold. The chemiluminescence spectra of these reactions have a wavelength maximum at 431 nm independent of the concentration of hydrogen peroxide. The results indicate that hydrogen peroxide is a necessary component in the chemiluminescent oxidation of the luminol by sodium hypochlorite.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 13 (1993), S. 289-297 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dual or multiple parameter flow cytometric analysis is developing into a powerful method for characterizing microbial populations. The distinguishing of the populations only by assignment of size/shape measurements by scattered ligth renders as not satisfactory.To differentiate between the cells, the employment of a specific fluorescence marker is absolutely necessary. Methods are presented for the flow cytometric determination of DNA and the polymer poly-β-hydroxybutyrate (PHB) content in three different bacterial strains. The measurement of the 3β-hydroxysterol content enables the differentation between yeast and bacterial organisms in mixed microbial populations. Monitoring the ratio of live to dead bacterial cells in soil or water samples, e.g. in pure culture systems, is shown.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 12 (1992), S. 365-375 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: To understand and control the dynamics of microbial growth and metabolism, a theoretical background based on segregated models is necessary, and therefore flow cytometry is the suitable measuring method.It is shown that additional information to the usual mean-value information, and to the well-known cytometric methods for determining DNA content and size/shape measurement by scattered light, like the distribution of membrane sterol content of baker's yeast, leads to a more detailed knowledge of growth dynamics.We have found, that a low content of membrane sterols is a characteristic of cells with suppressed proliferation activity, but necessary for high fermentation activity. Also, a high content of membrane sterols seems to enhance the viability and survival capability of harvested and dryed baker's yeast cells. Therefore, we recommend harvesting cells at a point of medium content of membrane sterols.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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