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  • 11
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; On-line coupling ; Ion-exchange membrane ; Ion-pair reagent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to enable the coupling of reversed-phase liquid chromatography (RPLC) with capillary gas chromatography (GC), the performance of an anion-exchange micromembrane device has been studied to remove the ion-pair reagent methanesulphonic acid from an acetonitrile/water LC eluent. The regenerant in the membrane was tetrabutylammonium hydroxide dissolved in acetonitrile/water, which effects an anion-exchange of methanesulphonate ions for regenerant hydroxide ions. The efficiency of the exchange process was found to be 99.9%. This enabled the direct introduction of the LC eluent, free of ions and with the proper acetonitrile/water ratio, into the GC. The applicability of the on-line LC-micromembrane-GC system has been illustrated for the potential drug eltoprazine, which is quantitatively recovered with a coefficient of variation for standard solutions of 3% at the 150 μg/ml analyte level.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Membrane-extraction disks ; On-line trace enrichment ; Polar pollutants ; Surface water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An on-line trace-enrichment system, using a bifunctional membrane extraction-disk cartridge, has been combined with a column liquid chromatography separation for the simultaneous determination of basic, neutral and acidic pollutants in surface water. The enrichment device consisted of a specially constructed holder containing both C-18 and cation-exchange disks. The holder can contain up to 25 disks of 0.5 mm thickness and 4.6 mm diameter. Before trace enrichment of 20 ml of surface water (pH 3.0), calcium ions were removed from the sample by means of an oxalic acid precipitation. Desorption of the cartridge was at elevated temperature using reversed-phase gradient elution; detection was performed with a diode-array UV absorbance detector. The detection limits for the test compounds in surface water are typically 0.5–2 μg/l; the calibration graphs are linear from the lower limit of determination up to 50 μg/l.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. An extensive study on the presence of nine organotin compounds (OTs) in a freshwater foodweb was made, using newly developed analytical procedures in order to obtain insight in accumulation and degradation processes. Tributyltin (TBT), Triphenyltin (TPT) and their degradation products were detected. Zebra mussels, eel, roach, bream, pike, perch, and pike perch and cormorant showed high OT body concentrations. At the lower trophic levels, phenyltin concentrations were higher in benthic species while butyltin concentrations were higher in pelagic species. This indicates that TBT is passed on primarily via the water, while TPT is passed on to a larger extent via the sediment. At the higher trophic levels, net bioaccumulation of TPT was greater than that of TBT, resulting in relatively higher TPT concentrations. High concentrations of biodegradation products of TBT, but not of TPT, were found in the livers of fish and birds, which indicates that TBT is more easily metabolized than TPT. A comparison with literature data of fish lethal body concentrations revealed that fish in the field may be endangered. With birds, the highest concentrations of OTs were present in liver and kidney and not in subcutaneous fat, which confirms that OTs accumulate via different mechanisms than traditional lipophilic compounds. As a whole the OT concentrations found in the foodweb may be considered to be quite alarming.
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract An extensive study on the presence of nine organotin compounds (OTs) in a freshwater foodweb was made, using newly developed analytical procedures in order to obtain insight in accumulation and degradation processes. Tributyltin (TBT), Triphenyltin (TPT) and their degradation products were detected. Zebra mussels, eel, roach, bream, pike, perch, and pike perch and cormorant showed high OT body concentrations. At the lower trophic levels, phenyltin concentrations were higher in benthic species while butyltin concentrations were higher in pelagic species. This indicates that TBT is passed on primarily via the water, while TPT is passed on to a larger extent via the sediment. At the higher trophic levels, net bioaccumulation of TPT was greater than that of TBT, resulting in relatively higher TPT concentrations. High concentrations of biodegradation products of TBT, but not of TPT, were found in the livers of fish and birds, which indicates that TBT is more easily metabolized than TPT. A comparison with literature data of fish lethal body concentrations revealed that fish in the field may be endangered. With birds, the highest concentrations of OTs were present in liver and kidney and not in subcutaneous fat, which confirms that OTs accumulate via different mechanisms than traditional lipophilic compounds. As a whole the OT concentrations found in the foodweb may be considered to be quite alarming.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 32 (1984), S. 45-52 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 35 (1985), S. 711-715 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An automated system for the monitoring of fermentations of filamentous fungi is described. The system is based on the on-line combination of ultrafiltration, for the removal of cellular and macromolecular material from the fermentation broth, and column liquid chromatography for analysis of the filtrate. The performance of one hollow-fibre and two planar ultrafiltration modules is evaluated. The maximum sampling frequency as well as prevention from clogging by mycelium is strongly dependent on the construction of the module, best results being obtained with a planar membrane and a relatively high flow rate (150 ml/min) of the broth through a single, wide-bore (3 mm) flow channel in the module. The method is used for the study of metabolic and regulatory processes of two different Aspergillus niger strains on multiple carbon sources. The selected system can be applied for at least 70 h without any negative effect on either the fermentation or the analytical system. Through an analysis frequency of once per hour detailed information regarding consumption and production of nine different compounds could be obtained.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An automated system for the monitoring of fermentations of filamentous fungi is described. The system is based on the on-line combination of ultrafiltration, for the removal of cellular and macromolecular material from the fermentation broth. and column liquid chromatography for analysis of the filtrate. The performance of one hollow-fibre and two planar ultrafiltration modules is evaluated. The maximum sampling frequency as well as prevention from clogging by mycelium is strongly dependent on the construction of the module, best results being obtained with a planar membrane and a relative high flow rate (150 ml/min) of the broth through a single, wide-bore (3 mm) flow channel in the module. The method is used for the study of metabolic and regulatory processes of two different Aspergillus niger strains on multiple carbon sources. The selected system can be applied for at least 70 h without any negative effect on either the fermentation or the analytical system. Through an analysis frequency of once per hour detailed information regarding consumption and production of nine different compounds could be obtained.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 83 (1984), S. 47-52 
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Umsetzung von Nitrat in Nitrosylchlorid und die nachfolgende Reaktion mit 8-Hydroxychinolin undp-Aminobenzolsulfonsäure ermöglicht den raschen Nachweis bis zu5 ng Nitrat im Wege einer Tüpfelprobe. Über55 Anionen und Kationen stören diesen Nachweis nicht, wenn vorher eine Dünnschicht-Chromatographie auf Kieselgel durchgeführt wird. Das Verfahren kann für die Bestimmung von Nitrat in Lebensmitteln und Wasser verwendet werden.
    Notes: Summary The conversion of nitrate into nitrosyl chloride, and subsequent reaction with 8-hydroxyquinoline andp-aminobenzene sulphonic acid allows the rapid detection of down to 5 ng of nitrate in a spot-test procedure. Over 55 anions and cations have been shown not to interfere if detection is preceded by thin-layer chromatography on silica. The method can be used for the determination of nitrate in food and water samples.
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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