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  • 1
    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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  • 2
    ISSN: 1612-1112
    Keywords: Colum liquid chromatography ; Ethylenethiourea in ground water ; Column switching ; Trace analysis ; Screening for ETU
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Column-switching with two C18 separation columns combined with UV detection at 233 nm has been used to determine ETU in ground water samples. The direct assay of ETU (limit of detection, 1 ppb) takes less than 10 min. For the determination of ETU down to a level of 0.1 ppb, preconcentration of ETU is achieved by a liquid-liquid extraction procedure allowing the analysis of at least 12 water samples per day. For both methods (1-ppb and 0.1-ppb level), the overall recovery (96 and 82%), the repeatability (4.5 and 4.3%) and the reproducibility (5.0 and 7.9%) are satisfactory (n=18 and 28, respectively). More than one hundred samples of ground water were analysed during a 10-month period; over 0.1 ppb of ETU (range, 0.1–300 ppb) was found in 30% of the samples tested.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-line preconcentration ; Polar pollutants ; Water (tap and surface)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An isocratic column liquid chromatographic system with UV absorbance detection at 230 nm has been developed for the rapid trace-level determination of a large number of polar pollutants in water. The systems contains two precolumns, in series, which are packed with a styrenedivinylbenzene (PLRP-S) polymer. The second precolumn is also loaded with sodium dodecylsulphate before use. Each precolumn is combined with a PLRP-S analytical column, and aqueous acetonitrile mixtures (pH 3) are used for the separation of neutral as well as acidic and basic pollutants. With 10-ml water samples the detection limits for all analytes, in tap water, are in the low to sub μg/l range. Relevant analytical data are reported and the advantage of using a dodecylsulphate-loaded precolumn over a cation-exchange precolumn is discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Chlorophenols in water ; Preconcentration ; Post-column photochemical dechlorination ; Electrochemical, UV and fluorescence detection ; Column switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A specific HPLC method has been developed for the trace analysis of lower chlorinated aromatic compounds. The method consists of an on-line preconcentration and a post-column reaction step. On-line preconcentration of mono- and dichlorophenols from aqueous samples has been performed using PRP1, a divinylbenzene-styrene copolymeric sorbent as packing material for both pre-and analytical column. Enrichment factors of over 300 were obtained compared to regular (100 μl) loop injections, even for the highly polar monochlorophenols. After reversed-phase separation, post-column photochemical dechlorination is carried out directly in the eluent stream, using a photochemical reactor. Upon dechlorination, fluorescent products are formed, which can be detected selectively. The resulting fluorescence signal shows a linear response to the quantity of solute present over 2 to 3 orders of magnitude (correlation coefficients: 0.990–0.98). For the mono- and dichlorophenols, the detection limit of the photoconversion method is in the lower nanogram range. The method is especially suitable for the analysis of complex matrices such as effluent water samples or biological fluids containing traces of the polar chloroaromatic compounds together with large amounts of other constituents, which interfere when using more general methods of detection like UV absorption. The potential of this technique for automation has been demonstrated by using a microprocessor-controlled column switching unit.
    Type of Medium: Electronic Resource
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