Effect of Ionic Liquids as Mobile-Phase Additives on Chromatographic Parameters of Neuroleptic Drugs in Reversed-Phase High-Performance Liquid Chromatography

Ionogenic basic compounds belonging to phenothiazine derivatives were analyzed in the reversed-phase system and were modified with the addition of three ionic liquids: 1-ethyl-3-methyl-imidazolium hexafluorophospate (EMIM PF6), 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIM PF6), and 1-butyl-3-methyl-imidazolium chloride (BMIM Cl). The effects of the concentration and the type of ionic liquid on the analytes' retention, peak symmetry, and efficiency were examined. The following trends increase analytes' retention factor and improve system efficiency: BMIM PF6EMIM PF6BMIM Cl. With its asymmetric cation enlarged with hydrophobic substituents and a chaotropic anion, BMIM PF6 appeared to be the most advantageous one. The isotherm of adsorption of this reagent presents a typical Langmuir course. By the application of high-performance liquid chromatography, lipophilicity parameters were established (lnkw, S, phi 0) for the investigated compounds. Chromatographic systems modified with ionic liquids were compared to buffered organic-aqueous mobile phase and eluent containing chaotropic salt additive.