Effects of ionic liquid on the separation of 2-chlorophenol and 2,4,6-trichlorophenol in RP-HPLC.

In this study, the use of ionic liquids as additives in the separation of 2-chlorophenol and 2,4,6-trichlorophenol in reversed-phase high-performance liquid chromatography is reported. The ionic liquids used were 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium methylsulfate ([EMIm][MS]), and 1-octyl-3-methylimidazolium methylsulfate ([OMIm][MS]), because of their high hydrophobicity and good solvating properties. The effects of the ionic liquid on retention factor and resolution, and the change of detector response using the different ionic liquids were studied. Separation with the [MS] anion ionic liquid in the eluent resulted in better resolution than with the [BF4] anion ionic liquid. The best result was achieved using 3.0 mM/L of [OMIm][MS] and 1.0 mM/L [EMIm][MS] as mobile phase additives.