Investigation of Non-Linear Chromatographic Retention Behavior for Two Homologous Series of Bis Analytes
Kelly, Kevin
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https://hdl.handle.net/2142/84366
Description
Title
Investigation of Non-Linear Chromatographic Retention Behavior for Two Homologous Series of Bis Analytes
Author(s)
Kelly, Kevin
Issue Date
1997
Doctoral Committee Chair(s)
Pirkle, William H.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Analytical
Language
eng
Abstract
Curved plots of retention factor vs. number of methylenes have been obtained for members of two homologous series of diamides. With alcohol modified mobile phases, plots of normalized HPLC retention factor vs. number of methylenes show maxima for retention for members of the homologous series of bis naproxen amides and bis 3,5-dinitrobenzoyl amides. The maximum retention and amount of curvature for each plot is column-independent, suggesting an analyte phenomena is being observed. Maximum retention for the bis 3,5-DNB amides is found for the homologues with 5-6 methylene groups in all solvents investigated. In contrast, maximum retention for the bis naproxen amide homologues with 3-8 methylene groups is correlated with the polarity of the mobile phase. Mono analytes of these two series do not show the same retention behavior but show normal chromatographic retention. The experimental results are interpreted in light of the analyte-specific equilibria associated with the folding of the bis derivatives. Mono analytes have no such competing mechanism available to them so normal retention behavior is both expected and found. In non-alcohol modified mobile phases, normal chromatographic retention behavior is found for both the bis- and mono-functional analytes of both series. This interesting experimental observation implicates a much more complicated phenomenon is occurring than simple folding of the bis analytes. Solvophobic effects may induce folding in homologues which otherwise find folding thermodynamically unfavorable increasing the complexity of the retention data.
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