ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Determination of the ionization constants of weak electrolytes by capillary zone electrophoresis (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 30-32 
    Details
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; Ionization constants ; Aromatic amines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary zone electrophoresis in untreated fused silica capillaries has proved suitable for the determination of the ionization constants of weak electrolytes. Several fundamental equations relating the electrophoretic mobilities of ionized solutes to hydronium ion concentrations in the running electrolyte have been verified experimentally. The observed dependence of the electrophoretic mobilities of weak bases and ampholytes on the pH of the electrolyte showed good agreement with predicted behavior. The pKa values calculated from electrophoretic mobility data obtained by capillary zone electrophoresis were reasonably close to those reported in the literature.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150108
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Capillary zone electrophoresis of biological substances with surface-modified fused silica capillaries with switchable electroosmotic flow (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 573-578 
    Details
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; Switchable electroosmotic flow ; Proteins ; Oligosaccharides ; Nucleotides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A surface modification has been developed which yields fused silica capillaries with switchable electroosmotic flow (anodal/cathodal). The capillary surface is a composite material consisting of unreacted silanol groups, a layer of positively charged quaternary ammonium functions, and a hydrophilic layer of long polyether chains. Because of the presence of positively and negatively charged groups, the net charge of the capillary surface can be varied from positive to negative by changing the pH of the running electrolyte, thus enabling manipulation of the magnitude and direction of the electroosmotic flow. The long polyether chains were effective in shielding biomacromolecules from the charged inner surface of the capillary, thus minimizing electrostatic interaction of the solutes with both unreacted silanols and the quaternary ammonium groups which had been introduced. As a consequence, high separation efficiencies were achieved with proteins, nucleotides, and a series of acidic oligosaccharides.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150903
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Chromatographic properties of zirconia-based stationary phases for ion exchange chromatography having surface bound cationic functions (1994)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 705-712 
    Details
    ISSN: 0935-6304
    Keywords: High performance liquid Chromatography ; Zirconia-based ion exchange ; Proteins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of non-porous, microspherical zirconia-based stationary phases with surface bound cationic functions have been introduced and evaluated in ion exchange chromatography of proteins and small acidic solutes. Different surface modification procedures were evaluated in the covalent attachment of weak, strong or hybrid anion exchange moieties on the surface of non-porous zirconia micropar-ticles. N,N-Diethylaminoethanol (DEAE) was used as the weak anion exchange ligand while glycidyltrimethylammonium chloride, which was covalently attached to poly(vinyl alcohol) layer (PVAN) on the zirconia surface, constituted the strong anion exchange moiety. Partially quaternarized poly(ethyleneimine) hydroxyethylated (PEI) was used as the hybrid type of anion exchange coating. DEAE-zir-conia microparticles acted as purely cation exchange stationary phases toward basic proteins indicating the predominance of electron donor-electron acceptor interaction (EDA) with surface exposed zirconium sites as well as cation exchange mechanism via electrostatic interaction with unreacted and unshielded hydroxyl groups. PVAN-zirconia stationary phase exhibited anion exchange chromatographic properties toward acidic proteins, but EDA interaction has stayed as an important contributor to solute retention despite the presence of a relatively thick layer of poly(vinyl alcohol) on the surface of the zirconia particles. The modification of zirconia surface with partially quaternarized PEI proved to be the most effective approach to minimize Lewis acidic metallic properties of the support. In fact, PEI-zirconia stationary phase operated as an anion exchanger toward acidic proteins and other small acidic solutes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240171005
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Coupled fused silica capillaries for rapid capillary zone electrophoresis of proteins (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 289-292 
    Details
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; Tunable electroosmosis ; Coated capillaries ; Coupled capillaries ; Protein ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel two-dimensional electrophoretic system for the control of electroosmosis in capillary zone electrophoresis has been developed and evaluated for rapid separations of proteins. The system comprises uncoated and polyether-coated fused silica capillaries coupled in series. An equation relating the average electroosmotic flow velocity in the coupled capillaries to the intrinsic electroosmotic velocities of the connected segments and their corresponding lengths has been derived and verified experimentally. This approach has the advantage of enabling the electroosmotic flow to be tuned independently of the applied voltage. As a consequence, rapid protein analysis at relatively low field strength was achieved without sacrificing the high separation efficiencies obtained with surface-modified capillaries.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150503
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Micellar electrokinetic capillary chromatography with in situ charged micelles: II. Evaluation and comparison of octylmaltoside and octylsucrose surfactants as anionic borate complexes in the separation of herbicides (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 127-138 
    Details
    ISSN: 1040-7685
    Keywords: micellar electrokinetic capillary chromatography ; in situ charged micelles ; herbicides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This report is an extension of our previous work involving the development of in situ charged micellar phases with adjustable surface charge density for micellar electrokinetic capillary chromatography (MECC) of neutral and charged herbicides. The micelles evaluated here are basically alkyldisaccharide-borate complexes in which the surface charge density can be conveniently varied by changing the operating parameters such as borate concentration and/or pH of the running electrolyte. The two alkyldisaccharide surfactants (i.e., octyl-β-D-maltopyranoside and octylsucrose), having the same alkyl tail but differing in the nature of the sugar polar head group, were compared and characterized over a wide range of conditions using neutral and acidic herbicides as model solutes. The effects of the operating parameters are discussed in terms of mobility, elution range parameter, capacity factor, peak capacity, and separation efficiency. The retention energetics of the micellar phases were studied using two homologous series, alkylphenylketones and alkylbenzenes. At constant micellized surfactant concentration, the two in situ charged micellar phases exhibited homoenergetic retention behavior toward the homologous solutes. On the other hand, even though the two surfactants differed by the nature of one sugar residue in their polar head groups, the micelles exhibited different hydrophobic character, with octylmaltoside yielding higher retention.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220060206
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Preparation of amino-zirconia bonded phases and their evaluation in hydrophilic interaction chromatography of carbohydrates with pulsed amperometric detection (1994)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 773-778 
    Details
    ISSN: 0935-6304
    Keywords: High performance liquid chromatography ; Amino-zirconia sorbents ; Carbohydrates ; Pulsed amperometric detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of non-porous, microspherical zirconia-based stationary phases with surface bound amine functionality have been introduced and evaluated in hydrophilic interaction chromatography (HILIC) of underivatized, neutral carbohydrates and anion exchange chromatography of nucleotides using pulsed amperometric detection and ultraviolet detection, respectively. Three aminopropyl alkoxysilane compounds were used in the surface modification of the non-porous zirconia support, namely 3-aminopropyltrimethoxysilane (monoamine), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (diamine), and trimethoxysilylpropyldiethylenetriamine (triamine). Due to the relatively low specific surface area of the non-porous zirconia support used in this study (ca. 7.3 m2/g), zirconia with surface coating of the triamine type yielded the best results as far as the separations of chitooligosaccharides and maltooligosaccharides are concerned. Since a non-porous zirconia could be readily modified with amine functionality via Zr—O—Si bonds, it is expected that all the three aminopropyl alkoxysilane compounds would yield satisfactory results with porous zirconia microparticles because of their much higher specific surface areas. Although the non-porous zirconia exhibited some limitations, the present study has demonstrated that microspherical zirconia particles are suitable supports for the production of polar sorbents for HILIC of carbohydrates. Another surface modification, which involved the activation of the zirconia surface with aldehyde groups followed by reductive amination with tetraethylenepentamine, was also evaluated. Although this chemistry would in principle yield sorbents with higher concentration in amine groups, the conversion of the majority of the primary amine groups of the tetraethyle-nepetamine molecules to secondary amine functions in the course of the reductive amination reaction have provided a stationary phase that did not afford satisfactory resolution for carbohydrates. However, this same stationary phase behaved as a weak anion exchanger and allowed the high resolution separation of nucleoside-5′-mono-, -di-, and triphosphates. Overall, the results obtained with zirconia-based hydrophilic sorbents paralleled those obtained on amino-silica bonded phases.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240171109
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Capillary zone electrophoresis of proteins with fused-silica capillaries having polymers and surfactants adsorbed onto surfactant moieties previously covalently bound to the capillary column surface (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2278-2284 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Fused-silica capillaries ; Capillary coating ; Hydroxypropylcellulose ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Fused-silica capillary columns having cationic surfactant moieties (CSM) covalently attached to the capillary inner walls were introduced for the separation of proteins by capillary zone electrophoresis (CZE). The CSM capillary coating proved to be useful in the separation of basic and acidic proteins when modified hydroxypropylcellulose (HPC), namely epoxybutane-HPC (EBHPC), was adsorbed to the primary CSM coating, yielding a hybrid coating (i.e., coating consisting of a covalenty bound ligand and an adsorbed ligand). The EBHPC layer rendered the capillary surface highly hydrophilic, thus permitting the separation of basic proteins with relatively high plate counts. Also, the CSM coating was useful for the separation of acidic proteins when the capillary wall had, in addition, a negatively charged polymer adsorbed to the surface, e.g., hyaluronic acid. In general, neutral and charged polymeric compounds could be readily adsorbed by the CSM coating, thus altering the zeta potential of the capillary and diminishing solute adsorption to the capillary surface. In other words, the sign of the zeta potential of the capillary surface could be tailored to be of the same sign as the charge of the analytes. Under these conditions, little or no solute-wall interaction could be observed due to electrostatic repulsion. Although the capillary surface was charged, the presence of adsorbed polymer suppressed or, in most cases, even eliminated the electroosmotic flow (EOF).
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191305
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Call for papers (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 3230-3230 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191829
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Capillary zone electrophoresis of biological substances with fused silica capillaries having zero or constant electroosmotic flow (1993)
    Weinheim : Wiley-Blackwell
    Electrophoresis 14 (1993), S. 396-406 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A series of capillary surface modifications entailing multilayered coatings were introduced and evaluated in capillary zone electrophoresis of biological substances, e.g., proteins, peptides, oligosaccharides and nucleotides. In one set of surface modifications, large molecular weight hydroxypropyl cellulose afforded “zero” flow capillaries, which were used as precursors for developing anodal flow capillaries. When “zero” flow capillaries were further functionalized with a charged polyethyleneimine layer to which a top polyether layer was covalently attached, the resulting anodal electroosmotic flow was relatively weak due to the high viscosity of the coated wall imparted by the hydroxypropyl cellulose layer. Capillaries with relatively strong and constant anodal electroosmotic flow were best achieved when the inner capillary surface was first chemically derivatized with methylated (i.e., quaternarized) polyethyleneimine hydroxyethylated. This hydroxylated and permanently charged polymeric coating yielded constant anodal flow regardless of electrolyte pH. The hydroxyl groups of the charged polymeric coating permitted the covalent attachment of polyether chains, which minimized electrostatic interaction between the positive charges of the polymeric layer and oppositely charged biopolymers. Under these conditions, rapid transport of acidic biopolymers past the detection point in the separation capillary could be achieved, and relatively high plate counts were obtained.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150140165
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Fused-silica capillaries with surface-bound dextran layer crosslinked with diepoxypolyethylene glycol for capillary electrophoresis of biological substances at reduced electroosmotic flow (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 617-624 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Capillary coating ; Proteins ; Acidic monosaccharides ; Sialooligosaccharides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: This report is concerned with the introduction of novel surface modification involving the covalent attachment of branched, high molecular weight dextrans and subsequent crosslinking with polyether chains on the inner surface of fused silica capillaries with the aim of producing hydrophilic capillaries with reduced electroosmotic flow (EOF). Three different molecular mass dextrans, namely 45, 71 or 150 kDa were covalently attached to the capillary surface, and subsequently crosslinked with diepoxypolyethylene glycol (PEG). This chemistry produced stable coating over a wide range of conditions including high and low pH aqueous solutions. Moreover, the various dextran-PEG-coated capillaries exhibited reduced electroosmotic flow. These features of the dextran-PEG coatings were useful for the separations of basic and acidic proteins, and provided high resolution separation for closely related acidic monosaccharides and sialooligosaccharidesPresented as a poster at Electrophoresis Forum '94, Munich, Germany, October 24-26, 1994.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150160199
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...