IONIC LIQUIDS AS MOBILE PHASE ADDITIVES IN REVERSED-PHASE HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

Ionic liquids are compounds of salt structure with melting point below 100°C and even 25°C known as room temperature ionic liquids. They have been widely investigated as new nonmolecular solvents exhibiting a wide range of changing properties, in many fields of analytical chemistry. This work reports on the use of 1-butyl-3-methylimidazolium of varying anion chaotropicity as a mobile phase additive for separation and chromatographic behavior studies of acidic, basic, and amphoteric compounds in reversed-phase liquid chromatography on two hydrophobic columns: Zorbax XDB-C18 and Zorbax SB-Phenyl. Satisfactory separations are achieved by the use of carefully optimized chromatographic systems modified with ionic liquids’ additives. The retention mechanism involving molecular interactions between analytes and additives and partitioning process between mobile phase and interphase created during equilibration process are discussed.