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  • 1
    Electronic Resource
    Electronic Resource
    Control of adsorption and solubility in gradient high-performance liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 557-563 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/methyl methacrylate) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and methyl methacrylate (MMA) were separated by both normal and reversedphase gradient chromatography. Both modes could be performed by sudden-transition gradients where the polymers were injected into a non-solvent whose polarity was either rather low (e.g.,n-heptane) or high (e.g., acetonitrile). Then the solvent strength of the starting eluent was rapidly increased to a given level by addition of dichloromethane. Under properly defined conditions, the sample components still remained on the column. Elution could be triggered off by the steady addition of another non-solvent whose polarity was opposite of that of the starting non-solvent. Thus, the mixture of five copolymers with MMA content ranging from 14 to 84% could be separated on a polar cyanopropyl column by injection inton-heptane and elution through acetonitrile (normal phase mode) and on a RP C18 column by injection into acetonitrile and elution throughn-heptane (reversed-phase mode), provided that in both modes about 30% dichloromethane was added to the starting non-solvent. The elution sequence in the reversed-phase mode was opposite to that in the normal-phase mode, obeying the approved polarity rules of chromatography in both cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268279
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  • 2
    Electronic Resource
    Electronic Resource
    Control of adsorption and solubility in gradient high performance liquid chromatography. Part 4. Sudden-transition gradient elution of styrene/ethyl methacrylate copolymers in reversed phase mode (1994)
    Springer
    Chromatographia 39 (1994), S. 170-174 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/ethyl methacrylate) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and ethyl methacrylate have been separated according to composition byn-heptane gradients on a C18 bonded phase after injection into acetonitrile and subsequent sudden transition to a concentration of either dichloromethane or tetrahydrofuran between 30 and 50% or 20 and 50%, respectively. Acetonitrile is a polar non-solvent for the copolymers under investigation and ensures proper retention of the samples on a non-polar stationary phase. Dichloromethane and tetrahydrofuran are good solvents of moderate polarity. The addition of, e.g., 30 vol% of one of these solvents increased the dissolution power of the starting eluent but not to the extent necessary for elution. The latter was achieved by the addition ofn-heptane, which is a non-solvent for the polymers investigated. Thus, its eluting power must be understood as the consequence of its modifying effect on the polarity of the eluent mixture. The higher the content of copolymer in ethyl methacrylate the earlier it was eluted. Since acetonitrile andn-heptane are only partly miscible, phase diagrams were measured after the addition of either tetrahydrofuran or dichloromethane as a third component. Homogeneous mixtures were obtained on addition of about 30% solvent (one of both of the latter).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274496
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  • 3
    Electronic Resource
    Electronic Resource
    Separation of copoly(styrene/acrylonitrile) samples according to composition under reversed phase conditions (1991)
    Springer
    Chromatographia 32 (1991), S. 107-112 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Styrene/acrylonitrile polymers ; Gradient elution ; Solubility effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copoly(styrene/acrylonitrile) samples (S/AN) have been repeatedly separated according to composition by gradient HPLC with alkane hydrocarbons as a starting eluent A and dichloromethane (DCM) or tetrahydrofuran (THF) as a solvent B. In these systems, retention increased with AN content of the copolymers. The chemical nature of the column packings used had almost no influence on the retention of S/AN samples. The present paper shows thatn-pentane andn-heptane, when used in a given volumetric gradient with DCM+20% methanol as a solvent B, lead to identical solution characteristics of S/AN on silica columns. A similar result was obtained on C18 columns withn-heptane or cyclohexane, whereas gradient elution with toluene as a starting eluent caused insufficient resolution. Reversed phase separation of S/AN copolymers could be achieved on polystyrene gel columns through gradients with methanol as a starting eluent and DCM or THF as a solvent B. In both systems, retention decreased with increasing AN content of the copolymers. The elution characteristics were almost linear in the range 0–20 wt% AN. This behaviour can be understood in the context of polymer solubility: in both systems, the solubility borderline of S/AN has a distinct maximum at about 25 wt% AN. Reversed phase separation was achieved at the lefthand slope of these curves where the dissolution of a sample with a higher AN content requires less DCM or THF solvent than the dissolution of copolymers which are poorer in AN. This idea predicts that samples with more than 25 wt% AN should elute later than S/AN whose composition is near to the solubility maximum. This indeed was found with a copolymer containing 36.2 wt% AN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325011
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  • 4
    Electronic Resource
    Electronic Resource
    Control of adsorption and solubility in gradient high performance liquid chromatography. Part 3. Sudden-transition gradient elution of styrene/ acrylonitrile copolymers (1994)
    Springer
    Chromatographia 38 (1994), S. 749-755 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/acrylonitrile) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and acrylonitrile could be separated according to composition by gradient elution through methanol after injection inton-heptane and sudden addition of 50, 60, or 70 vol% tetrahydrofuran. The peak sequence was the same as with a common binary gradientn-heptane/tetrahydrofuran, i.e., retention increased with acrylonitrile content of the samples. With copolymers containing 37, 31, or 26% acrylonitrile, the elution characteristics in the ternary systems could be logically extrapolated towards the points measured in the corresponding binary gradient system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269631
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