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  • Articles: DFG German National Licenses  (5)
  • Electronic Resource  (5)
  • On-line trace enrichment  (3)
  • Electrodialytic sample treatment  (2)
  • 1
    Electronic Resource
    Electronic Resource
    On-line trace enrichment — column liquid chromatography of polar pollutants in surface water using bifunctional membrane-based extraction-disk cartridges (1994)
    Springer
    Chromatographia 39 (1994), S. 239-245 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02274506
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Trace enrichment of polar pollutants from water and the influence of humic substances (1993)
    Springer
    Chromatographia 37 (1993), S. 13-19 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polar pollutants in water ; On-line trace enrichment ; Humic substances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A practical liquid chromatographic early-warning system for polar pollutants in water ought to have detection limits at a level below a microgram per litre. Using ultraviolet absorbance detection this normally necessitates trace enrichment of the samples. In this study ten different sorbents have been tested with respect to their enrichment capacity. The hydrophobic polymeric PLRP-S material, in combination with a C-18 modified analytical column, proved to be the best choice. The influence of humic substances, present in surface water, was also studied. Lowering of the sample pH, resulted in a significant increase in the interferences due to the humic substances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272181
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Miniaturization of solid-phase reactors for on-line post-column derivatization in narrow-bore liquid chromatography (1985)
    Springer
    Chromatographia 20 (1985), S. 453-460 
    Details
    ISSN: 1612-1112
    Keywords: Narrow-bore column liquid chromatography ; Post-column derivatization ; Solid-phase reactors ; Catalytic hydrolysis ; On-line trace enrichment ; Immobilized enzyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of solid-phase reactors for post-column derivatization in narrow-bore HPLC (1.0mm i.d. analytical columns) is evaluated. Two systems are described, viz. for the determination of N-methylcarbamate pesticides and for that of urea and ammonia. The solid-phase reactor is packed with a strong anion exchange resin and urease immobilized on silica, respectively, to effect the catalytic hydrolysis of the solutes eluting from the analytical column. In both systems, the hydrolysis product is reacted with o-phthalaldehyde followed by fluorescence monitoring. Analytical data are presented and band broadening from various parts of the reaction detector system is discussed. An on-line trace enrichment procedure via a micro precolumn is descried for the trace level determination of N-methylcaramates in surface water samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02344785
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Electrodialytic sample treatment coupled on-line with high-performance liquid chromatography (1990)
    Springer
    Chromatographia 30 (1990), S. 361-366 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrodialytic sample treatment ; On-line coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An electrodialytic sample treatment method coupled on-line with high-performance liquid chromatography (EDIST-HPLC) is discussed in this paper. The performance of EDIST as a function of the donor-phase (sample solution) flow rate, the voltage applied over the electrodialysis block, and the time of dialysis has been studied using the basic drug ephedrine as a model compound. Enrichment of the analyte by a factor of 10–20 was possible. The determination of human plasma spiked with ephedrine is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02328498
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical models for electrodialytic sample treatment in trace analysis by liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 460-468 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrodialytic sample treatment ; Computer models ; Analyte enrichment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Basic considerations for analyte enrichment and recovery obtainable by electrodialysis as a sample treatment method are given. Equations are derived which describe the dependence of the concentration profiles of ionic compounds on the electric field strength in a set-up with stagnant donor and acceptor solutions. It is shown that analyte recovery increases when less ion-selective membranes are used in the electrodialysis cell. Computer models are used to estimate the analyte enrichment for a flowing donor (sample) and a stagnant acceptor phase. About 10-fold enrichment can be obtained in an electrodialytic sample treatment system within 20 min under maximum current conditions. A compromise has to be found between analyte recovery and the donor (sample) flow rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278763
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    Paper (German National Licenses)
    Fulltext
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