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  • 1
    Electronic Resource
    Electronic Resource
    The preparation of non-extractable methylphenylpolysiloxane stationary phases for capillary column gas chromatography (1982)
    Springer
    Chromatographia 15 (1982), S. 335-340 
    Details
    ISSN: 1612-1112
    Keywords: Capillary gas chromatography ; Fused silica capillary columns ; Crosslinked phenyl polysiloxanes ; Non-extractable stationary phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of methylphenylpolysiloxane polymers and their use in the preparation of crosslinked, non-extractable stationary phases for fused-silica capillary columns are described. By preparing more viscous phenyl-containing polymers than are commercially available, stationary phase films of these polymers could be efficiently coated on fused-silica capillary columns and stabilized by a free radical crosslinking mechanism using peroxides. Four methylphenylpolysiloxane polymers containing different phenyl concentrations were prepared. These included three polymers containing 50% phenyl and one polymer containing 70% phenyl. Two of the 50% phenyl polymers had one phenyl and one methyl group attached to each silicon atom. One of these also had 1% vinyl incorporated. The third 50% phenyl polymer was synthesized in such a way that one half of the silicon atoms had two phenyl groups attached while the rest contained dimethyl groups. The 70% phenyl polymer also had 4% vinyl incorporated. Due to the intrinsic thermal stability of these phenyl phases and the enhanced film stability achieved by crosslinking, the 70% phenyl phase could be utilized up to 400 °C. Using the methods described in this paper, highly efficient and thermally stable fused silica capillary columns coated with crosslinked methylphenylpolysiloxane stationary phases can be successfully prepared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02259213
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  • 2
    Electronic Resource
    Electronic Resource
    Static coating of capillary columns using mixed solvents (1983)
    Springer
    Chromatographia 17 (1983), S. 451-453 
    Details
    ISSN: 1612-1112
    Keywords: Static coating ; Mixed solvents ; Capillary gas chromatography ; Capillary supercritical fluid chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Mixed solvents in coating solutions were employed to facilitate (lower temperatures and shorter times) the static coating of capillary columns. Different volume ratios of mixed solvents used in the coating solutions do not affect the quality of capillary columns coated with stationary phases of different polarity. Small diameter (〈100 μm i.d.) capillaries of up to 50 m long were successfully coated with a methylphenylpolysiloxane (50% phenyl) for use in supercritical-fluid chromatography. In addition, an 80 m×0.31 mm i.d. capillary was statically coated with Superox 20 M (0.25 μm film thickness) in a 1∶1n-pentane/methylene chloride mixture at 55 °C. The coating time was only 7 hrs, and the resultant column exhibited a total of 170,000 theoretical plates (k′=5.5).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262929
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  • 3
    Electronic Resource
    Electronic Resource
    Deactivation of small-diameter fused-silica capillary columns for gas and supercritical fluid chromatography (1984)
    Springer
    Chromatographia 18 (1984), S. 362-366 
    Details
    ISSN: 1612-1112
    Keywords: Deactivation of columns ; Capillary gas chromatography ; Capillary supercritical fluid chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to prevent plugging during deactivation of small diameter (50 μm i.d.) capillary columns for gas and supercritical fluid chromatography, various high temperature deactivation methods were employed. Pure hexamethyldisilazane and hexamethyldisiloxane (a substitute for D4) were dynamically coated on the column, while a film (0.05 μm) of OV-101 was statically coated, before high temperature (450°C) treatment. Excellent deactivated columns were obtained, and no significant difference in column activity was observed using any of these three methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262481
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of surface hydroxyl concentration on glass and fused silica capillary columns (1982)
    Springer
    Chromatographia 15 (1982), S. 584-586 
    Details
    ISSN: 1612-1112
    Keywords: Surface hydroxyl quantification ; Siliceous capillary columns ; Capillary gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The concentration of surface hydroxyl groups on three types of capillary columns was determined by exchanging the hydroxyl protons with tritium. The tritium was quantified by combustion to tritiated water followed by scintillation counting. The number of hydroxyl groups on a leached and presumably hydroxylated Pyrex glass capillary column was found to be about 2.8 groups per square nanometer. This value was slightly less than the 4.6 groups per square nanometer that is generally accepted for a fully hydroxylated porous silica. Dehydroxylation of the same glass by heating at 600°C left only 0.4 groups per square nanometer while an untreated fused silica had only 0.2 groups per square nanometer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02280379
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of viscosity on stationary phase stability in capillary column gas chromatography (1982)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 5 (1982), S. 413-416 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Stationary phase stability ; Stationary phase viscosity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: With recent advances in column technology it is now possible to prepare highly efficient, very inert, and thermally stable capillary columns coated with nonpolar polysiloxane stationary phases. Unfortunately, the same degree of success has not been achieved for some of the more polar polysiloxane phases. A parameter that has been studied little in the past in relation to stationary phase film stability is the viscosity of the stationary phase. In this paper the efficiency and stability of coated columns are correlated to the viscosity of the phase. Due to their structure, the viscosity of the phenyl-containing polysiloxanes change rapidly with temperature and hence, thin-film coatings are not stable at elevated temperatures. By using high viscosity phenyl-containing methylphenylpolysiloxanes which were recently synthesized, efficient and stable columns have been prepared.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240050804
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  • 6
    Electronic Resource
    Electronic Resource
    Multi-element selective radio frequency plasma detector for capillary gas chromatography (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 75-81 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Element selective detection ; Radio frequency plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A radio frequency plasma detector for element specific detection in gas chromatography is described. The detector is comprised of a radio frequency (300 kHz) discharge between electrodes in helium, and utilizes a low-resolution emission spectrometer to monitor selected spectral emission lines produced when the helium discharge decomposes and excites the atomic constituents in the chromatographic column effluent. The spectrometer is tuned to an atomic emission line in the near-infrared portion of the spectrum, and the emission intensity from the discharge region of a selected line is used to monitor the concentration of the element producing that line. Acceptable detector sensitivity was achieved by the use of a high-throughput optical system. Selectivity was achieved by a combination of correct line selection, plasma and carrier gas purification, and plasma gas doping.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110120
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  • 7
    Electronic Resource
    Electronic Resource
    Azo compounds for free radical crosslinking of polysiloxane stationary phases (1983)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 6 (1983), S. 371-374 
    Details
    ISSN: 0935-6304
    Keywords: Free radical crosslinking ; Capillary gas chromatography ; Azo compounds ; Nonextractable Polysiloxane stationary phases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: There has been much effort spent in recent years developing the technology for free radical crosslinking of polysiloxane polymers to prepare capillary columns coated with thermally stable and nonextractable stationary phases. Organic peroxides have been used extensively as the free radical initiators for the in situ polymerization of the stationary phases. However, these peroxides adversely affect the phase polarity and column activity. Seven azo compounds were studied for crosslinking efficiency. Azo compounds can be used as free radical initiators to prepare nonextractable stationary phases without the adverse effects caused by peroxides.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240060705
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  • 8
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    Diffusive electron acceleration at SNR shock fronts and the observed SNR radio spectral indices (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The radio synchrotron emission from relativistic electrons in shell supernova remnants (SNRs) provides a unique opportunity to probe the energy distribution of energetic electrons at their acceleration site (SNR shock fronts). This information provides insight into the acceleration mechanism(s). The implications of these observations for the diffusive (first-order Fermi) acceleration of electrons at the SNR shock fronts are discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Nineteenth International Cosmic Ray Conference. Conference Papers: Invited Rapporteur, Highlight, Miscellaneous, Volume 9; 4 p
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    On the anomalous component (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The so-called anomalous cosmic ray component, which occurs at energies of about 10 MeV/nucleon and consists only of He, N, O, and Ne, has been a subject of interest for more than a decade. The origin of this component is generally considered to be interstellar neutral gas that is ionized and accelerated in the solar wind. The mechanism and the location for the acceleration, however, remains an unsolved problem. A model is used which includes the effects of gradient and curvature drifts and considers the implications of observed spatial gradients of the anomalous component for the location of the acceleration region. It is concluded that if drifts are important the acceleration region cannot lie at the solar poles. It is also concluded that there is no single region for the acceleration which can account for both the observed intensities and gradients in models which include drift effects.
    Keywords: SPACE RADIATION
    Type: SH-4.6-6 , 19th Intern. Cosmic Ray Conf - Vol. 5; p 180-183; NASA-CP-2376-VOL-5
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    A simple model for the formation of 'reflected', 'intermediate', and 'diffuse' ion distributions upstream of earth's bow shock (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Detailed energetic ion and low-frequency wave experiments on ISEE 1, 2, and 3, have established correlations between the types of ion populations and waves observed to exist in the earth's foreshock region. The present calculation has the objective to quantitatively test the picture obtained for the earth's foreshock region. An analysis is conducted of the coupled spatial and temporal evolution of upstream protons and hydromagnetic waves by means of a simple model in which the protons are represented by counterstreaming beams which resonate with hydromagnetic waves, exciting the outward propagating modes and damping the inward propagating modes at a single wave number.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 39-45
    Format: text
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    NASA TECHNICAL REPORTS
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