Adsorption phenomena in chromatography [electronic resource] : Studies on nonlinear behavior and the hydrophobic effect.

1991

1 online resource (265 p.)

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Source: Dissertation Abstracts International, Volume: 53-03, Section: B, page: 1494.

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Two important aspects of modern liquid chromatography--the dynamics of nonlinear systems and the thermodynamics of hydrophobic adsorption--are examined. Nonlinear adsorption behavior encountered at high concentrations is studied theoretically with particular emphasis on the phenomenon of selectivity reversal, which may occur upon change in the concentration of the separands or of the mobile phase modulator. Selectivity reversal hinders separation so an understanding of such behavior is important in order to correctly diagnose and prevent it. The multicomponent Langmuir adsorption isotherm model is found to be inadequate to describe the behavior, and instead thermodynamically consistent multicomponent isotherms generated by the ideal adsorbed solution (IAS) theory are employed. Gradient elution with modulator dependent and separand concentration dependent selectivity reversal is studied for the first time, and methods to predict separation behavior under conditions of column overload are given. Separand concentration dependent selectivity reversal in displacement chromatography is analyzed by a new method and three operating regions are identified--one where separated bands appear in their original order, another where they appear in reversed order, and a third where complete separation is impossible and azeotropes form. Azeotropes had previously been thought not to occur in such systems. Displacement chromatography of proteins in hydrophobic interaction chromatography (HIC) is demonstrated experimentally for the first time. In one case selectivity reversal occurs and is analyzed using the theoretical principles introduced in this work. Changes in the temperature facilitate separation in this case. New expressions are introduced to account for the effect of specific salt interactions and temperature in linear HIC of proteins. Finally, a theoretical study is presented that advocates the use of elevated temperature for rapid chromatographic analysis of macromolecules.

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English

July 12, 2011

Thesis (Ph.D.)--Yale University, 1991.

Yale University.