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  • Liquid chromatography  (26)
  • Springer  (26)
  • American Meteorological Society
  • Blackwell Publishing Ltd
  • International Union of Crystallography (IUCr)
  • Nature Publishing Group
  • Springer Nature
  • Springer Science + Business Media
  • 1980-1984  (26)
  • 1960-1964
  • 1945-1949
  • 1982  (26)
Collection
Publisher
  • Springer  (26)
  • American Meteorological Society
  • Blackwell Publishing Ltd
  • International Union of Crystallography (IUCr)
  • Nature Publishing Group
  • +
Years
  • 1980-1984  (26)
  • 1960-1964
  • 1945-1949
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 15 (1982), S. 595-598 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; High-speed liquid chromatography ; Small-particle LC columns ; Injector bypass ; Column lifetime in LC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In the case of liquid chromatography columns packed with small (3–5 μm) particles and utilized at relatively high flow rates, pressure pulses associated with the sample injection process (caused by a short-duration interruption in mobile phase flow to the column during injection) may result in a reduction of column lifetime. This detrimental effect can be eliminated by the utilization of specially constructed sample injection valves incorporating properly desinged bypass loops. The paper investigates in detail the effect of pressure pulses, describes the criteria and performance of the bypass systems, and documents column life time and performance.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 15 (1982), S. 83-85 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Tricyclic antidepressants ; Solid phase extraction ; Serum ; Clinical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Five common tricyclic antidepressants are separated on a silica column using an aqueous eluent. The tricyclics are concentrated from serum using an adsorption procedure on a solid phase Sep PakTM C18 cartridge. The method appears to be adequate for monitoring therapeutic levels of these drugs.
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  • 3
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Complex solvent mixtures ; Optimization of solvent composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Four different methods of calculation of retention in ternary mobile phases were compared and it was found that the simple calculation based only on two values of the capacity factors (one for each binary system that composes the ternary mobile phase) provides the accuracy of prediction that is, at least, comparable to the other methods of calculation that require a large number of preliminary experiments. The deviations from ideal behaviour in ternary solvent mixtures are discussed; some sources of errors can be avoided, at least partially, using binary systems of adequate compositions for preparation of ternary mobile phases. Several examples show the comparison of calculated and experimental selectivities in ternary solvent systems. A simple calculation can be used for rapid selection of an adequate ternary (or more complex) mobile phase, if it is necessary to achieve the separation of a given sample mixture.
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  • 4
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Reverse-phase ; 3 μm packing materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The efficiency of high-performance liquid chromatography columns packed with 5 μm and 3 μm reverse-phase octadecylsilane packing materials has been evaluated using four test mixtures. Both stopped flow and valve injection have been used and typical efficiencies are given.
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  • 5
    ISSN: 1612-1112
    Keywords: Phosphorescence, room-temperature ; Detection, continuous flow ; Liquid chromatography ; Halogenated componds ; Dibenzofurans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is shown that sensitized room-temperature phosphorescence in liquid solutions can be successfully applied as a detection method in continuous flow and chromatographic systems. The limits of detection for a series of halogenated naphthalenes and biphenyls obtained by plug injection are roughly the same as those in batch experiments — in the subnanogram region. Liquid chromatograms of mixtures of PCBs, PCNs and polychlorodibenzofurans are given.
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  • 6
    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.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 15 (1982), S. 437-444 
    ISSN: 1612-1112
    Keywords: Detection ; Liquid chromatography ; Reversed phase ; Ion-pairing probes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Compounds without own detector response can be detected and quantified by a UV-absorbing or fluorescent, ion-pairing probe in reversed-phase liquid-solid systems. Charged as well as uncharged samples give response by affecting the distribution of the probe between the phases. The probe is usually a hydrophobic organic ion. It is included in the mobile phase, which also contains a counter ion and an ion of the same charge as the probe, both fairly hydrophilic. The choice of properties and concentrations of the hydrophilic ions is essential for the response since too low and too high distribution of the mobile phase ions to the adsorbent will make the system insensitive. It is with UV-absorbing probes possible to get a response corresponding to a molar absorptivity of more than 3000 for ionic samples. Fluorescent probes have given 3–5 times higher sensitivity. Uncharged compounds give as a rule lower response. A combination of two UV-absorbing probes with different charge gives a considerable improvement of the response for samples with low retention. A simplified theoretical model for the detector response is suggested on the basis of detailed studies of the concentration changes in the eluted mobile phase.
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  • 8
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Photochemical reaction detection ; Chemical post-column reduction ; Fluorimetric detection ; Air segmented flow systems ; Non-aqueous reversed-phase chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new photochemical reaction method for the on-line fluorimetric detection of natural vitamin K homologs was developed. In addition to its high sensitivity, the method features an interesting selectivity for the determination of these compounds in a complex matrix such as human serum. The formation of different photolysis products as a function of reaction conditions, and the optimalisation of a segmented flow reaction system will be discussed. The results indicate that the method is 4 times more sensitive than UV detection, and at least as selective as fluorescence detection after post-column chemical reduction.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 15 (1982), S. 476-478 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Mass detector ; Carbohydrates ; Lipids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The mass detector was investigated as an alternative to RI detection for carbohydrate and lipid analyses with high pressure liquid chromatography. The instrument was found to be more sensitive than most RI detectors and, as gradient elution could also be carried out, the resulting chromatograms showed improved resolution.
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  • 10
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Nucleobases ; Nucleosides ; Silica gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of nucleobases and nucleosides on unmodified silica with dichloromethane-methanol-water mixtures has been systematically investigated. The degree and order of retention can be varied over a wide range by changing the pH, the type and concentration of the acidic additives and by the methanol and water content of the mobile phase. The retention process cannot be considered as simple adsorption but rather as a very complex mixed distribution process of adsorption and absorption including the involvement of ion-pair formation. Further data on the effect of the type of silica (source of supply) on retention behaviour, column efficiency and column reproducibility are reported. The practical application of unmodified silica for the separation of nucleobases and nucleosides is demonstrated by the analysis of a hydrolysate of calf thymus DNA.
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