Molecule HPLC Retention Relationships

In recent years, three-dimensional quantitative structure biological activity relationship methods known as comparative molecular field analysis (CoMFA) has been applied to construct a 3D-QSRR model for prediction of retention data. The CoMFA 3D-QSRR model is obtained by systematically sampling the steric and electrostatic fields surrounding a set of analyte molecules. Next, the differences in these fields are correlated to the corresponding differences in retention. The CoMFA model was successfully applied to HPLC retention data of polycyclic aromatic hydrocarbons [60]. 

Warmuth [34] when they adopted NPC for the analysis of supermolecules, such as hemicarcerplexes. Hemicarcerplexes are complexes formed with hemi-carcerand host and guest molecules. As shown in Figure 5-6, hemicarcerands possess a very hydrophobic structure with molecular weight over 2000 and is insoluble in protic solvents. A normal-phase HPLC method was developed using a silica column with dichloromethane and diethylether as the mobile-phase system. The authors demonstrate that the chromatographic retention of hemicarcerplexes is mainly dominated by its size. Furthermore, a linear relationship between the logarithmic retention factor and the size of the hemicarcerplexes was observed for linear guest molecules independent of their polarity. 

Lipophilicity of a molecule is measured by its distribution behavior in a biphasic system either liquid-liquid (partition coefficient in 1-octanol-water) or solid-liquid (retention in RP-TLC or RP-HPLC) systems. According to definition suggested by lUPAC lipophilicity expresses the affinity of a molecule for a lipophilic environment. A reference scale representing lipophilicity appears to be the solute distribution between octanol and water. Berthod Carda-Broch (Berthod Carda-Broch) proposed another lipophilicity scale measuring ionic liquid BMIM PFg-water distribution constants. Relationship between the obtained values and respective octanol-water coefficients for a series of aromatic compounds differing in acid-base properties revealed that only the neutral compounds or ionizable ones with zwitterionic properties showed similar distribution behavior in the... 

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