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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 433-436 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Miniaturization ; Planar chip technology ; Silicon and glass microstructures ; Small volume optical detector cell ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Miniaturization of separation columns implies equally reduced vol- umes of injectors, detectors, and the connecting channels. Planar chip technology provides a powerful means for the fabrication of micron-sized structures such as channels. This is demonstrated by two examples. An optical absorbance detector chip exhibits the expected behavior of a 1 mm optical path length cell despite its volume of 1 nL. A capillary electrophoresis device allows integrated injections of 100 pL samples, efficiencies of 70,000 to 160,000 theoretical plates in 10 to 20 seconds, and external laser-induced fluorescence detection at any capillary length of choice between 5 and 50 mm.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Column switching ; Planar chip technology ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel concept for repeated column switching in capillary electrophoresis is presented. Theoretical considerations predict high plate numbers per volt. Using micromachining techniques, a planar glass structure has been fabricated, which contains four capillaries of 20 mm length arranged in a square. Laser fluorescence detection gave a cycle time of 70 s for 2.5 kV applied. After five cycles a theoretical plate number of 40,000 was reached.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A Nafion membrane was tested as a new tool for a fast and easy sample pretreatment for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) measurements. This membrane material was used for ion exchange and carbohydrate purification with minimal quantities of sample solution. An ion exchange method for carbohydrates was developed and demonstrated on a Dextran sample. The cations of the original sample were replaced within minutes by potassium or cesium ions. Another feature of this membrane was the fact that proteins and peptides adsorb on the acid surface. This behavior was investigated as a purification step for carbohydrates with high peptide and protein impurity concentrations. It was found that oligosaccharide libraries from rat- and mouse IgG mass spectra can be obtained clearly in the presence of high peptide impurities.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 809-814 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The aim of this article was to study the influence of different matrix molecules on the quality of matrix-assisted laser desorption/ionization mass spectra of oligosaccharides. An important criterion was the sample preparation, i.e. the crystallization process leading to the matrix from which the analytes were desorbed and investigated. Quality criteria were, among others, the resulting molecular peak intensity, the mass resolution, and the suppression of unwanted matrix peaks. It was found that a mixture of 2,5-dihydroxy benzoic acid (DHB) and 1-hydroxy isoquinoline (HIC) in a weight ratio of 3:1 was best suited for the analytical investigation of oligosaccharides. In addition, this matrix mixture was found to be quite tolerant against all kinds of buffers, salts, and even additives such as sodium dodecyl sulfate (SDS). Furthermore, we determined the different affinities of the alkaline metals to the carbohydrates and found that cesium and potassium ions ionize oligosaccharides about three times better than sodium ions and therefore have an important influence on the quantum yield.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The effect of buffer conditions  -  varying in salt type, pH, and concentration - on the separation of 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS)-labeled monosaccharides and complex-type carbohydrates was investigated. Different buffer systems for high and low electroosmotic flow conditions were chosen: a phosphate and a citriate background electrolyte, each at pH 2.5, a phosphate buffer, pH 9.0, and a borate buffer at pH 9.5. All buffer systems displayed differences in resolution and selectivity. Phosphate and borate buffer demonstrated the greatest selectivity changes for ANTS-labeled carbohydrates. While separation in the phosphate system relies mainly on differences in the charge-to-mass-ratio, additional selectivity can be achieved with borate complexation of glycoconjugates. The use of borate buffers improved monosaccharide separations whereas complex carbohydrates showed a loss in resolution. The citrate background electrolyte at low pH caused no significant changes in the separation performance. The pH 9.0 phosphate buffer showed a reversed migration order of the ANTS conjugates with a decreased resolution, compared to the pH 2.5 phosphate buffer, due to the strong electroosmotic flow generated under high pH conditions. An ovalbumin-derived oligosaccharide library demonstrates the significance of buffer selectivity for complex carbohydrate separations. The separation in the acidic phosphate and the alkaline borate buffer generates a different pattern and only the combination of both buffer systems allows an appropriate assessment of sample complexity.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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