^#.^t6: Ionic Liquid Additives to Mobile Phases
Numerous mobile-phase manipulations have been tested to suppress undesirable silanol effects in liquid chromatography. The most studied modiers of mobile phase were primary, secondary, tertiary, and quaternary amine additives [4,5]. Nahum and Horvath recommended them as additives to the eluent employed in reversed-phase chromatography of inorganic substances to suppress the deleterious effect of free silanolic groups in the stationary phase . The class of amine additives involves monoamines, such as dimethyloctylamine (DMOA), ethanolamine, hydroxylamine, triethanolamine, triethylamine (TEA), propylamine, and quaternary tetramethylammonium chloride as well as diamines such as ethylenediamines . The role of the amine additive is to interact with silanol sites and reduce its interaction with basic analytes . In practice, the most effective are tertiary amines that can interact with a silica support through the same mechanism as a basic solute.