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
    Evaluation of flow restrictors for open-tubular supercritical fluid chromatography at pressures up to 560 atm (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 269-274 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Flow restrictor ; Integral restrictor ; Tapered restrictor ; Frit restrictor ; Polysiloxane ; Polydimethylsiloxane, PDMS ; Polyethylene glycol, PEG ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proper performance of the flow restrictor is of crucial importance in supercritical fluid chromatography. This is especially the case when the restrictor is the interface between the chromatographic column and a detector operating at lower pressure than the column. The performance of three types of fixed flow restrictor, the “tapered”, the “integral”, and the “frit”, was examined. The test mixtures chosen covered a range of polarities and molecular weights. Polydimethylsiloxane with an average molecular weight of 10,000 was used as a low polarity probe. Two polyethylene glycol mixtures were chosen as higher polarity probes. One consisted of a mixture of polyethylene glycol standards with average molecular weights ranging from 200 to 1450. The other polyethylene glycol mixture had an average molecular weight of 2000. The polydimethylsiloxane standard did not elute when the frit restrictor was used. Satisfactory results were obtained when the tapered and integral restrictors were employed. All three restrictors provided satisfactory results for polyethylene glycol oligomers eluting up to approximately 40.5 MPa (400 atm). However, for oligomers eluting above this pressure, the peaks merged into a broad hump with the frit restrictor, while the tapered and integral restrictors provided satisfactory separations. The integral restrictor produced more evenly spaced, more well resolved peaks at the high-pressure end of the chromatograms than did the tapered restrictor. This is shown to be due to differences in the rates of increase in mobile-phase velocity with increasing pressure for the two restrictors.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240160502
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Use of SFC/MS for the confirmation of peak identities in the SFC/FID chromatogram of olestra (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 4 (1992), S. 295-303 
    Details
    ISSN: 1040-7685
    Keywords: open tubular supercritical fluid chromatography-mass spectrometry ; ammonia chemical ionization ; electron ionization ; direct fluid introduction interface ; cryopumping ; Ultramark 3200 ; perfluorinated polyether ; sucrose polyester ; SPE ; olestra ; noncaloric fat replacement ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Open tubular supercritical fluid chromatography (SFC) with flame ionization detection (FID) has been used for characterizing olestra, a mixture of fatty acid sucrose esters. In this publication, we describe SFC/mass spectrometry (SFC/MS) of olestra using the direct fluid introduction interface. Chemical ionization spectra were used in confirming SFC/FID peak identities. Electron ionization SFC/MS of olestra was also investigated. Both major and minor component peaks in the SFC chromatogram of olestra were characterized. A slight modification of the interface-probe tip was necessary for operation at higher temperature. A procedure was developed for tuning and calibrating the instrument in the 10-4000-u mass range, chemical ionization mode using Ultramark 3200, a perfluorinated polyether. The use of additional pumping in the form of liquid nitrogen cooled cryopumps was key in providing good signal-to-noise ratios for the latereluting (i.e., eluting at higher mobile phase pressures and flow rates) olestra components.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220040402
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Characterization of low molecular weight poly(acrylic acid) samples by capillary supercritical fluid chromatography and capillary supercritical fluid chromatography-mass spectrometry (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 2 (1990), S. 181-187 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; mass spectrometry ; poly(acrylic acid) ; linear polycarboxylate ; derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low molecular weight poly(acrylic acid) (PAA) samples were derivatized to increase their solubilities in the supercritical mobile phase, CO2. tert-Butyldimethylsilyl ester derivatives provided better chromatographic performance and molecular weight range than did trimethylsilyl or methyl esters. Individual oligomers were resolved through approximately n = 28. Higher oligomers, up to approximately n = 45 (corresponding to an underivatized molecular weight of more than 3300), were eluted from the column but were not resolved. Ammonia chemical ionization and electron ionization supercritical fluid chromatography-mass spectrometry data revealed that the PAA terminal groups of the samples studied were sulfonate and hydrogen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220020405
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Modified ionspray interface for supercritical fluid chromatography/mass spectrometry: Interface design and initial results (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1087-1094 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A pneumatically assisted electrospray liquid chromatography/mass spectrometry interface has been modified for use with open-tubular supercritical fluid chromatography (SFC). The modified interface houses the SFC flow restrictor within the spray device. A sheath-flow liquid of methanol or methanol/water containing ammonium acetate flows coaxially to the restrictor. The addition of the sheath-flow liquid results in the ionization of analytes known to be in a neutral charge state during the chromatographic separation. The sheath-flow liquid also allows for the independent operation of the chromatograph and the mass spectrometer. Both could be operated under optimum conditions. The operation of the interface was optimized using a solution of poly(dimethylsiloxane) in CO2 introduced by continuous infusion. We also report the application of the modified instrument to samples containing amines and propoxylated alcohols.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091202
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Comparison by capillary SFC and SFC-MS of soxhlet and supercritical fluid extraction of hamster feces (1991)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 401-406 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Supercritical fluid extraction, SFE ; On-line combination ; SFC-MS ; Hamster feces ; Lipids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Components of hamster feces ranging from low molecular weight fatty acids through the expected range of triglycerides have been eluted in a single SFC run with simultaneous pressure and temperature programming. Temperature programming from 140°C to 240°C was required to provide optimum conditions for separation of the fatty acids and to move the elution region of the sterol esters away from that of the triglycerides. Data from chemical ionization and electron impact mass spectrometry of compounds separated by SFC were used to confirm identities suggested by retention measurements and to provide tentative identities of unknown compounds.SFC with flame ionization detection was used to compare Soxhlet extraction, off-line supercritical fluid extraction (SFE), and on-line SFE of the feces. Although samples obtained by Soxhlet extraction and SFE produced very similar chromatograms, SFE required far less time and consumed much smaller quantities of organic solvent.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240140610
    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...