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  • 1
    Electronic Resource
    Electronic Resource
    Development of an eluotropic series for the chromatography of Lewis bases on zirconium oxide (1992)
    s.l. : American Chemical Society
    Analytical chemistry 64 (1992), S. 863-873 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00032a008
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  • 2
    Electronic Resource
    Electronic Resource
    The role of Lewis acid-base processes in ligand-exchange chromatography of benzoic acid derivatives on zirconium oxide (1992)
    s.l. : American Chemical Society
    Analytical chemistry 64 (1992), S. 853-862 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00032a007
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  • 3
    Electronic Resource
    Electronic Resource
    Manipulation of chiral resolution for isoxazoline-based IIb/IIIa receptor antagonists using various mobile phase additives in subcritical fluid chromatography (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 338-342 
    Details
    ISSN: 0899-0042
    Keywords: additive ; selectivity ; efficiency ; modifier ; subcritical fluid chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Subcritical fluid chromatography (SubFC) using a carbon dioxide-methanol mobile phase is used for the chiral resolution of IIb/IIIa receptor antagonist enantiomers. The chiral resolution of three analogs, each containing two chiral centers, is optimized using various mobile phase additives. The effects that acidic, basic, and neutral additives have on retention, efficiency, and resolution are examined. The additive that gives the best resolution was found to be dependent upon the functionality and charge of the chiral analyte. For charged analytes, additives that act as competing ions of the same charge as the chiral analyte dramatically improve efficiency and resolution. Resolution of neutral chiral analyte enantiomers is also greatly affected by the choice of mobile phase additive. Chirality 10:338-342, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Optimization of chiral resolution using packed columns with carbon dioxide-based mobile phases (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 672-677 
    Details
    ISSN: 0899-0042
    Keywords: chiral SFC ; SubFC ; SFC ; methanol modified CO2 ; efficiency ; selectivity ; retention ; packed column SFC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optimization of chiral resolution, using carbon dioxide based mobile phases, must take into consideration the individual contributions of analyte retention, selectivity, and efficiency. Each of these factors may be independently affected by changes in pressure, temperature, or state of the mobile phase. The ability to control retention by different means reflects an advantage of carbon dioxide based mobile phases over conventional HPLC mobile phases. Utilization of this advantage requires that the effects of each of these factors on each contributor to resolution be known. The cumulative effect that each of these variables has on retention, selectivity and efficiency suggests that maximum resolution is obtained using low pressures and temperatures. Maximum resolution (at fixed k′) results from low temperatures and high pressures. The latter may be of more practical importance when speed of analyses and detection limits are considered. Chirality 9:672-677, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature effects for chiral separations using various bulk fluids in near-critical mobile phases (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 693-698 
    Details
    ISSN: 0899-0042
    Keywords: supercritical fluid chromatography ; subcritical fluid chromatography ; HFC-134a ; 1,1,1,2-tetrafluoroethane ; carbon dioxide ; chiral selectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As supercritical fluid chromatography becomes more accepted as a facile means for the separation of chiral compounds, the need for mobile phases that can readily solubilize these polar compounds grows. Prior studies suggest that HFC-134a may prove suitable due to its very high eluotropic strength compared to carbon dioxide-based mobile phases. A comparison is made between ethanol-modified carbon dioxide, HFC-134a, and decafluoropentane as to their relative eluotropic strength, selectivity, and efficiency for three chiral compounds using a Whelk O-1 chiral bonded phase. The bulk component of the mobile phase was found to have relatively little effect on chiral selectivity over the range of 5° to 95°C. Chirality 9:693-698, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of Mobile Phase Components on the Separation of Polypeptides Using Carbon Dioxide-Based Mobile Phases (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 74-78 
    Details
    ISSN: 0935-6304
    Keywords: Polypeptides ; subcritical fluid chromatography ; supercritical fluid chromatography ; carbon dioxide ; additives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The effect of mobile phase modifier and additive on the chromatographic properties of various small polypeptides was explored under subcritical conditions. A polymeric column was used to separate various enkephalin analogs, bradykinin, and oxytocin using a carbon dioxide-based mobile phase with either an ethanol or a 2-methoxyethanol modifier. The role of the modifier was found to be secondary to that of the mobile phase additive. As progressively stronger acidic mobile phase additives were used, the peak profiles of the various polypeptides improved and retention decreased. Heptadecafluorooctanesulfonic acid was found to be the most useful additive for these types of solutes under near-critical conditions, while the potassium salt of heptadecafluorooctanesulfonic acid failed to elute any of the polypeptides. At low temperatures, pressure gradients with a carbon dioxide/ethanol/heptadecafluorooctanesulfonic acid ternary mobile phase produced reasonably good peak profiles with the polymeric column.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Functional group selectivity using fluoroform as a mobile phase for supercritical fluid chromatography (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 475-482 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; fluoroform ; carbon dioxide ; mobile phases ; selectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The eluotropic strenght and chromatographic selectivity of fluoroform is compared to that of carbon dioxide and methanol-modified carbon dioxide. Naphthalene derivatives were used as probe solutes in capillary supercritical fluid chromatography to determine the effects of fluid type, pressure, and temperature on selectivity and retention. Fluoroform is much stronger in eluotropic strengh than carbon dioxide or methanol-modified carbon dioxide at the same temperature and pressure. Under the same reduced conditions, fluoroform is lower in eluotropic strength than carbon dioxide. Specific interactions between hydrogen bond accepting functional groups and fluoroform are observed. Functional groups capable of accepting hydrogen bonds contribute less of an increase in retention when using fluoroform while those capable of dispersive interactions contribute less of an increase in retention when using carbon dioxide.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220060507
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrofluorocarbon and perfluorocarbon mobile phases for capillary supercritical fluid chromatography (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 551-556 
    Details
    ISSN: 1040-7685
    Keywords: hydrofluorocarbon ; perfluorocarbon ; mobile phases ; supercritical fluid ; selectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The eluotropic strength of several hydrofluorocarbon and perfluorocarbon supercritical fluids is examined using capillary supercritical fluid chromatography. The results obtained are compared with carbon dioxide, fluoroform, and carbon dioxide modified with 5% methanol. Various naphthalene derivatives are used to determine differences in functional group selectivity between these fluids. Specific hydrogen bonding interactions are observed between hydrogen bond donating hydrofluorocarbon fluids and naphthalene derivatives with hydrogen bond accepting functional groups. Unexpectedly, perfluorocarbon fluids are much stronger in eluotropic strength than carbon dioxide, fluoroform, or methanol-modified carbon dioxide.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220060604
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  • 9
    Electronic Resource
    Electronic Resource
    Study of the Effect of Mobile Phase Additives on Retention in Reversed Phase HPLC Using Linear Solvation Energy Relationships (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 427-434 
    Details
    ISSN: 0935-6304
    Keywords: Linear solvation energy relationship ; retention ; mobile phase ; stationary phase ; additives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Linear solvation energy relationships (LSERs) were used to delineate which specific intermolecular interactions are responsible for changes in retention for a variety of well characterized analytes when acidic and basic additives were used in reversed phase HPLC. The effects of trifluoroacetic acid, triethylamine and a combination of trifluoroacetic acid and triethylamine on the LSERs were compared to those observed in the absence of additives. These effects were examined using four different mobile phase modifiers and five different stationary phases. Trifluoroacetic acid alone and in combination with triethylamine produced LSER regression coefficients nearly identical to those obtained with no additive present in the mobile phase. Triethylamine alone produced different LSER regression coefficients from the other systems unless the mobile phase contained trifluoroethanol as the mobile phase modifier, or the stationary phase consisted of a polymeric support.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Comparision of varuious bulk fluids and modifiers as near-crtical mobile phases on a polymeric column using linear solvatio energy realationships (1997)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 631-637 
    Details
    ISSN: 0935-6304
    Keywords: High Perfromance liquid chromatography ; supercritical fluid chromatography ; Selectivity ; Hydrogen bonding ; Linear solvation energy relationships ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear solvation energy realationships (LSERS) were used to qunatitatively compare the relative contributions of dipolarity/polarizability, hydrogen bonding, and other types of intermolecular interactions to retention and selectivity using various bulk moblie phase component. Using experimental condition which differ only by the compostion of the bulk moble phase component, the factors which cause selctivity to differ between HPLC, subcritical fluid chromatography and supercritical fluid charomatography were decovoluted. Heptance-based HPLC mobile phases showed superior selectivities towards analytes which differ in hydrogen bond donating ability, gas-to-hexadecane partion coefficint and dipolarity/ploarizability. subcritical fluid chromatography with HFC-134a (1, 1, 1, 2-tetrafluoroethane) as the bulk fluid produced superior seclectivities for which differ in hydrogen bond accepting ability and execess molar refraction properties. Many of these factors showed temperature dependences which act to attenuate or accenture the particular intermolcular interaction.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240201203
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