Roles of Ionic Liquids in High Performance Liquid Chromatography pp. 373-394
Authors: (Aurora Martín Calero, Verónica Pino, Juan H. Ayala, Ana M. Afonso, Department of Analytical Chemistry, Nutrition and Food Science, University of La Laguna, Spain)
Abstract: Ionic liquids (ILs) are a class of non-molecular ionic solvents with low melting points resulting from combinations of organic cations and various anions. ILs have many unique properties including wide viscosity ranges, almost negligible vapor pressure, high thermal stability, and a multitude of varying solvation interactions. These outstanding properties justify the high number of applications of these novel solvents in different fundamental and application areas, including analytical sciences. High-performance liquid-chromatography (HPLC) is a powerful analytical technique in which ILs have also found a variety of applications. The separation of basic compounds in HPLC still remains problematic due to the silanol interactions. The poor performance seen with basic compounds has been partially addressed through the development and introduction of the so-called base-deactivated materials. Nevertheless, addition of alkylamines (such as triethylamine) and other amino quenchers to the mobile
phase does not fully remove the deleterious effect of free silanols on the retention of basic analytes, even when employing the purified and least acidic silica supports.