Competitional hydrophobicity driven separations under RP‐LC mechanism: Application to sulfonylurea congeners

Abstract

Retention of a model set of sulfonylurea compounds has been studied under RP-LC conditions, considering competitional effects brought by different alcohols (ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, and 1-octanol) used as additives in the organic component of the mobile phase (methanol). The capacity factors determined for the model compounds decreased with the increase of the hydrophobic character of the organic additive in the mobile phase. The amount of the additive within the organic component of the mobile phase was kept constant (1% as volumetric ratio). Retention was studied at different mobile phase compositions (aqueous to organic component ratios). Different functional fitting models were used to correlate retention to the content of the organic component in the mobile phase. Extrapolation of retention expressed as capacity factor to a mobile phase composition free of organic component is well correlated to the hydrophobic characteristics of the organic additives. The adsorption model was used for tuning the experimental find-outs. The possibility of controlling retention through the competitive effects induced by hydrophobic additives in the mobile phase is highlighted.

Retention prediction in reversed‐phase liquid chromatography systems with methanol/water mobile phases containing different alkanols as additives

“…Fine‐tuning of difficult separations is possible using ternary mobile phases in either isocratic 1–5 or gradient elution mode 6–10. However, the commonly used organic modifiers in RP‐LC systems are methanol (MeOH) and acetonitrile (MeCN) and only few publications, to our knowledge, focused on enhancing the selectivity using some relatively uncommon organic modifiers 11–15. In most of these studies, straight‐chain upper alkanols at low concentration were used either as organic modifiers in binary solvent mixtures 11, 12 or as additives together with MeOH or MeCN in ternary mobile phases 14, 15 to modify and improve the separations.…”

“…However, the commonly used organic modifiers in RP‐LC systems are methanol (MeOH) and acetonitrile (MeCN) and only few publications, to our knowledge, focused on enhancing the selectivity using some relatively uncommon organic modifiers 11–15. In most of these studies, straight‐chain upper alkanols at low concentration were used either as organic modifiers in binary solvent mixtures 11, 12 or as additives together with MeOH or MeCN in ternary mobile phases 14, 15 to modify and improve the separations. However, no systematic study for the combined effect of the content of the main organic modifier (usually MeOH) as well as of the type and the concentration of the additive on solute retention has been reported in literature.…”