Identification of ionic liquid components by RP-HPLC with diode array detector using chaotropic effect and perturbation technique.

Sodium hexafluorophosphate, perchlorate and tetrafluoroborate were applied as the ion-pair reagents in reversed-phase chromatography of several imidazolium-based ionic liquids. The optimization of the retention was performed by changing the kind of organic modifier (methanol, acetonitrile), concentration and the kind of the ion-pair reagents in the mobile phase and the column kind (Zorbax SB-C18, Zorbax SB-Phenyl, Zorbax SB-CN, Zorbax SB-NH2 and Supelcosil LC-F). The selectivity of the proposed chromatographic systems according to the cation kind was compared on the basis of the resolution of ionic liquid mixture. The perturbation method was applied to identify the anion kind. The formation of ion-associated complexes between promethazine as counter-cation and chaotropic anions controlling their retention was confirmed.