Library

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
    Contribution of interfacial resistance to plate height in open tubular gas chromatography (1989)
    s.l. : American Chemical Society
    Analytical chemistry 61 (1989), S. 2165-2171 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00194a010
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    On the occurrence and characteristics of intense low-altitude electric fields observed by Freja (1995)
    Springer
    Annales geophysicae 13 (1995), S. 704-712 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract High-resolution measurements by the double probe electric field instrument on the Freja satellite are presented. The observations show that extremely intense (up to 1 V m−1) and fine-structured (〈1 km) electric fields exist at auroral latitudes within the altitude regime explored by Freja (up to 1700 km). The intense field events typically occur within the early morning sector of the auroral oval (01-07 MLT) during times of geomagnetic activity. In contrast to the observations within the auroral acceleration region characterized by intense converging electric fields associated with electron precipitation, upward ion beams and upward field-aligned currents, the intense electric fields observed by Freja are often found to be diverging and located within regions of downward field-aligned currents outside the electron aurora. Moreover, the intense fields are observed in conjunction with precipitating and transversely energized ions of energies 0.5-1 keV and may play an important role in the ion heating. The observations suggest that the intense electric field events are associated with small-scale low-conductivity ionospheric regions void of auroral emissions such as east-west aligned dark filaments or vortex streets of black auroral curls located between or adjacent to auroral arcs within the morningside diffuse auroral region. We suggest that these intense fields also exist at ionospheric altitudes although no such observations have yet been made. This is possible since the height-integrated conductivity associated with the dark filaments may be as low as 0.1 S or less. In addition, Freja electric field data collected outside the auroral region are discussed with particular emphasis on subauroral electric fields which are observed within the 19–01 MLT sector between the equatorward edge of the auroral oval and the inner edge of the ring current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-995-0704-9
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Modification of HPTLC-plates by in situ chemical bonding with non-polar and polar organosilanes (1980)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 345-350 
    Details
    ISSN: 0935-6304
    Keywords: Thin-layer chromatography, HPTLC ; Chemical modification of HPTLC-plates ; Organosilanes, polar and non-polar ; Zwitter character of modified silica surface ; Advantageous separation through plate modification ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method has been developed for the preparation of modified silica plates for high performance thin-layer chromatography (HPTLC). Some typical organosilanes were thus allowed to react in situ with the silica of Merck HPTLC-plates. This method was found to be highly reproducible, simple and cheap. Non-polar plates were prepared and compared with commercial plates from Merck, Whatman and Macherey-Nagel. Modification with cyanodecyltrichlorosilane resulted in plates that showed good coverage, efficiency and low residual silica activity. Silica modified with a multifunctional silane has different properties in different organic solvents. It will appear to be non-polar in a polar solvent and vice versa. New advantageous separation systems are thus made feasible by the presence of cyano groups on the plate.The utility of modified thin-layer plates is demonstrated by the separation of some homologues of p-hydroxybenzoic acid esters and of some polycyclic aromatic hydrocarbons.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240030707
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Guest editorial (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 208-208 
    Details
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240090402
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Examination of the properties of different 20% phenyl-substituted polymethylsiloxane stationary phases for capillary chromatography (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 3 (1991), S. 459-465 
    Details
    ISSN: 1040-7685
    Keywords: gas chromatography ; supercritical fluid chromatography ; open tubular columns ; methylphenyl polysiloxanes ; stationary phase immobilization ; polycyclic aromatic compounds ; triacylglycerols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three polysiloxanes, each having 20% phenyl substitution, have been evaluated for use as stationary phases in fused silica open tubular columns for gas and supercritical fluid chromatography. The columns were coated with PS-090 which had been treated in an aluminum pan in order to improve immobilization properties, OV-7, and a newly synthesized phase, Polymer S.Excellent columns were prepared with PS-090; however, treatment in the aluminum pan was an uncontrolled process, and the reproducibility of polarity may be questioned. For comparison, OV-7 could not be immobilized, but columns coated with this phase showed good thermal stability. The silanol terminated Polymer S was immobilized via a mechanism involving scission of phenyl groups; thus polarity was decreased after immobilization. However, columns for which Polymer S was immobilized in the presence of a cross-linking reagent maintained their polarity. Such columns showed very good chromatographic performance. These columns were applied to the separation of polynuclear aromatic compounds by GC and to the analysis of extracts from a thermomechanical pulping white water and lichen by SFC.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220030511
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Performance of silica-bonded quinolinol as a selective stationary phase for packed capillary supercritical fluid chromatography (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 223-228 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; packed capillary columns ; stationary phases ; silica-bonded 8-quinolinol ; fatty acid methylesters ; azaarenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selective stationary phases are of crucial importance in packed column supercritical fluid chromatography (SFC), and a potentially powerful selective stationary phase, silica-bonded 8-quinolinol, has been evaluated. Its performance was compared with that of an aminopropyl modified silica. The 8-quinolinol columns could be used at temperatures up to 150°C, while the aminopropyl columns were degraded above 90°C. The general performance of the quinolinol column was very good when utilizing a mobile phase containing a polar modifier. Reduced plate heights of 4.8 to 3.8 and symmetrical peaks were obtained. Further, the quinolinol phase showed excellent selectivities under supercritical conditions. This was demonstrated by the separation of fatty acid methylesters and azaarenes. In addition, changes in selectivity could readily be made by loading with metal ions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220060305
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    New silarylene/methylphenylsiloxane copolymer stationary phase for open tubular gas chromatography (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 3 (1991), S. 497-503 
    Details
    ISSN: 1040-7685
    Keywords: gas chromatography ; open tubular columns ; immobilized silarylene/siloxane stationary phase ; methyl/phenyl silicone ; polycyclic aromatic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new silanol-terminated silarylene/siloxane copolymer, having 30% phenyl and 1.5% vinyl substitution, has been evaluated for use as a stationary phase in gas chromatography. The polymer was found to be auto-cross-linkable. The highest degree of immobilization (90%) was obtained at relatively low temperatures (300°C). The auto-cross-linking at lower temperatures might be due to a silanol catalyzed reaction of vinyl groups. At higher temperatures (350-370°C) scission of phenyl groups and the formation of branched structures are the dominating immobilization reactions. Column polarity is thereby decreased.Thermal stability was excellent at 370°C after conditioning at this temperature. The utility of the columns was illustrated by the separation of polycyclic aromatic compounds.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220030604
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Current aspects of stationary phase immobilization in open tubular column chromatography (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 2 (1990), S. 62-68 
    Details
    ISSN: 1040-7685
    Keywords: statlonary phases ; immobilization ; open tubular columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In situ stationary phase immobilization in principle can be attempted in two different ways: using thermal methods or radical-initiated reactions. Thermal immobilization, in general, is applied for the preparation of columns to be used at ultra-high temperatures, and radical-initiated immobilization can be applied in most other cases. For polar, narrow-bore, and thick-film columns, low immobilization temperatures are preferred. The reactions involved in the different immobilization methods are described in this review, and the advantages and disadvantages of current immobilization methods are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220020204
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Enantioseparation of amino acids and dipeptides using vancomycin as chiral selector in capillary electrophoresis (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 1938-1944 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Enantiomers ; Vancomycin ; Amino acids ; Dipeptides ; Optimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Vancomycin was applied as chiral selector for the enantiomeric separation of derivatized amino acids and dipeptides. The influence of vancomycin concentration, pH and presence of 2-propanol in the buffer were examined in order to find optimal separation conditions. Optimization was by factorial design. Further, chiral separation of derivatives prepared with three different reagents was compared. These reagents were 9-fluorenylmethyl chloroformate (FMOC), 2-(9-anthryl)ethyl chloroformate (AEOC) and dansyl chloride (dansyl). Optimum resolution was at high vancomycin concentrations, while optimum efficiency was at low vancomycin concentrations. As a consequence of the very high enantioselectivity of vancomycin, the vancomycin concentration below the amount necessary for maximal resolution can be used. Separation efficiency was relatively low, and this could be attributed to adsorption of the selector at the capillary wall. Three factors led to decreased adsorption: application of a pH above the zero mobility pH value, low vancomycin concentrations and the presence of 2-propanol. For amino acids, the resolutions of the different derivatives were: dansyl 〉 AEOC 〉 FMOC, while for dipeptides, the highest selectivity was with AEOC.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150171222
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Chiral separation of DL-peptides and enantioselective interactions between teicoplanin and D-peptides in capillary electrophoresis (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 943-949 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Enantiomers ; Macrocyclic antibiotics ; Teicoplanin ; Dipeptides ; Tripeptides ; Optimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Teicoplanin has been evaluated as a selector for enantioseparation of di- and tripeptide derivatives in capillary electrophoresis. Separation variables such as type of buffer, pH, concentrations of teicoplanin and organic modifier were examined. Optimal separation conditions were obtained by means of factorial design experiments. The effects of teicoplanin concentrations below and above its critical micellar concentration (CMC) and of acetonitrile (ACN) on the separation were demonstrated. The use of a high concentration of ACN resulted not only in increased selectivity, but also in improved separation efficiency. Electroosmotic flow was observed to be largely independent of the concentrations of teicoplanin under the optimized conditions. Good repeatability of migration times was obtained. The interactions between teicoplanin and D and L peptides were studied, and it was found that, for some peptides, teicoplanin exhibited enantioselective interaction only with the D-form. Somewhat lower separation efficiencies were thus observed for the strongest interacting (D-form) peptides. Chiral separation of 15 DL-peptide derivatives was achieved in less than 10 min.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180615
    Library Location Call Number Volume/Issue/Year 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...