Investigation of Non-Linear Chromatographic Retention Behavior for Two Homologous Series of Bis Analytes

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Kelly, Kevin

Contributors dc:contributor

• Pirkle, William H.

• Chemistry, Analytical

Language dc:language

eng

Identifier

(MiAaPQ)AAI9737155

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/84366