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  • 1
    Electronic Resource
    Electronic Resource
    On-line chromatographic pretreatment of samples with varying salt concentrations for capillary electrophoresis (1997)
    Springer
    Chromatographia 44 (1997), S. 581-588 
    Details
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; On-line LC-CE ; Sample pretreatment ; Matrix effects ; Benzoic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various methods are currently under investigation to improve concentration detection limits in capillary electrophoresis (CE). Stacking and isotachophoresis coupled in-line with free-solution electrophoresis are the techniques most frequently used. Samples containing a high and/or varying salt concentration, such as urine and serum, are difficult to handle: usually a significant loss in electrophoretic efficiency is observed compared with samples possessing a low electric conductivity. In the present paper an alternative approach is developed, i.e. a liquid chromatographic (LC)-type of sample pretreatment is coupled on-line with CE. To demonstrate the feasibility of this approach, the separation of three model compounds (benzoates) in water containing up to 400 mM of sodium chloride is studied using a 50 mM borate CE buffer of pH 9.5. The direct injection of samples with high salt concentrations in CE results in peak splitting and/or serious band broadening. These problems are not encountered when using the present LC-CE system. In addition, the detection limits are hardly influenced by the salt concentration of the sample; this underlines the robustness of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466659
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  • 2
    Electronic Resource
    Electronic Resource
    On-line dialysis solid-phase extraction coupled to capillary electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2944-2949 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Dialysis ; Sample pretreatment ; Serum ; Sulfonamides ; Urine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A fully automated dialysis solid-phase extraction (SPE) sample preparation procedure is coupled on-line to capillary electrophoresis (CE) for the first time. The system is used to determine sulfonamides in serum and urine. The dialysis unit serves to remove proteins and particulate matter. Reconcentration of the analytes is performed with a small SPE column while (in)organic salts and other interferences are removed simultaneously. Finally, the analytes are desorbed and injected, via a homemade interface, into the CE system. Limits of detection (LOD) of 0.05-0.1 and 0.05-0.3 μg/mL are obtained in urine and serum, respectively. The within-day and between-day precisions are in the range of 2-6% and 3-8%, respectively, for a concentration of five times the LOD. The dialysis SPE-CE system was used over a period of six months for the analysis of over 500 serum and urine samples without problems such as clogging of the CE capillary or SPE column.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191625
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  • 3
    Electronic Resource
    Electronic Resource
    Analyte identification in capillary electrophoretic separation techniques (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2753-2776 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Capillary electrochromatography ; Analyte identification ; Spectrometric detection ; Review ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A review on applications of on-line hyphenation in capillary electrophoresis and capillary electrochromatography for the identification of migrating analytes is presented. There is an urgent need for unambiguous analyte identification by combining spectral information and observed migration times, because the parameters influencing the migration times and separation efficiencies in these separation techniques are not easily controlled, especially when real samples containing unknown interferences have to be analyzed. The spectrometric techniques covered here are ultraviolet and visible radiation (UV/Vis) absorption, fluorescence including fluorescence line-narrowing spectroscopy, Raman spectroscopy, nuclear magnetic resonance and mass spectrometry. Attention is essentially confined to literature reports in which the extra information provided by the detector is really used for identification purposes, especially in real-life samples, while the interfacing as such and analyte detectabilities in standard solutions are only briefly discussed. This article covers an extensive fraction of the literature published on this topic until the beginning of 1998.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191604
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  • 4
    Electronic Resource
    Electronic Resource
    Separation of twenty-one naphthalene sulfonates by means of capillary electrophoresis (1996)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 99-104 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Micellear electrokinetic chromatography ; Organic modifiers ; Naphthalene sulfonates ; Surface water ; Thermostatting ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The production and use of naphthalene sulfonates can easily cause pollution of surface and other types of waters. In the present study, capillary electrophoresis in combination with UV absorption detection was used to separate 21 amino- and hydroxy-substituted naphthalene sulfonates which included multiple isomeric compounds. The influence of various parameters such as pH (which turned out to be extremely important), temperature of the surrounding air flow, and the use of buffer additives (micelles, cyclodextrins, organic modifiers) was studied. Complete separation of all analytes including the isomers, was achieved in two runs with a 50 mM boric acid/borate buffer, containing either 100 mM sodium dodecylsulfonate or 15% acetonitrile. The limits of detection obtained for the individual compounds typically were 20μgI-1. River water samples spiked at this concentration level could be analysed using a simple three-step sample clean-up procedure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240190208
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  • 5
    Electronic Resource
    Electronic Resource
    At-Line Solid-Phase Extraction Coupled to Capillary Electrophoresis: Determination of Amphoteric Compounds in Biological Samples (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 183-187 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; interfacing ; sample treatment ; serum ; solid-phase extraction ; sulfonamides ; urine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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