Abstract
The basic retention mechanisms of reversed-phase and hydrophilic-interaction liquid chromatography (HILIC) were quantitatively analyzed using simple molecular mechanics (MM) calculations. The model bonded phases were composed of an alkyl chain bonded to siloxane-like molecules. The head of the alkyl chain was a hydroxyl group, used to study retention mechanisms of HILIC. The standard analytes were benzoic acid, aniline, benzene, water, and acetonitrile. The molecular interaction (MI) energy values of the van der Waals (VW) force were predominant for the reversed-phase chromatography, and those of hydrogen bonding (HB) were predominant for HILIC. Up to 5 units of methylene affected the MI.
Highlights
Retention mechanisms of various chromatographic methods such as gas chromatography, liquid chromatography, chiral chromatography, and affinity chromatography have been quantitatively studied using computational chemistry
The molecular interaction (MI) energy values of the van der Waals (VW) force were predominant for the reversed-phase chromatography, and those of hydrogen bonding (HB) were predominant for hydrophilic-interaction liquid chromatography (HILIC)
A simple model experiment was carried out in silico to obtain a quantitative explanation of hydrophobic and hydrophylic mode chromatography, for the effect of alkyl chain length as described excluding ion-exchangers and zwitter ion phase used for HILIC; the retention mechanism was inconclusive because unspecified experimental conditions were provided
Summary
Retention mechanisms of various chromatographic methods such as gas chromatography, liquid chromatography, chiral chromatography, and affinity chromatography have been quantitatively studied using computational chemistry. HILIC columns were classified using physico-chemical descriptors, and the retention mechanisms were intensely discussed; the results could not be adopted as a general rule, and may only be attributed to their specific test settings, varying under different elution conditions [10] These above-mentioned problems are the basic problems in quantitatively studying the stationary phase selectivity. A simple model experiment was carried out in silico to obtain a quantitative explanation of hydrophobic and hydrophylic mode chromatography, for the effect of alkyl chain (ligand) length as described excluding ion-exchangers and zwitter ion phase used for HILIC; the retention mechanism was inconclusive because unspecified experimental conditions were provided. The limitation of the alkyl chain (ligand) length was studied using a computational chemical analysis
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