Non-aqueous capillary electrophoresis in acetonitrile using ionic-liquid buffer electrolytes

The use of non-aqueous solvents in analysis has become a distinct field of interest in capillary electrophoresis (CE), and is designated to here as 'non-aqueous capillary electrophoresis (NACE)". Organic solvents are of interest in capillary elect ro-separations because they extend the range of application of CE techniques to more hydrophobic species, addressing one of the main limitations, of this method. Changing the buffer electrolyte composition alters mobility in different ways, which include alteration of the ionic charge due to acid dissociation, alteration of the effective size of the ion by complexation and alteration of its mobility due to interaction with buffer additives. The dialkylimidazolium-based, liquid organic salts ("ionic liquids") are used as buffer electrolytes in this study. Their properties are governed by strong, proton donor-acceptor and orientation interactions. A selected application of separations of water-insoluble dyes in acetonitrile that were previously not accessible using conventional CE methodology are discussed. Anionic part of ionic liquid changes the general electrophoretic mobility of the system as well as the concentration of ionic liquid. Separation of analytes is achieved because of dissociation of analytes in the presence of ionic liquids in the separating medium. The migration order of analytes is based on differences in the effective charge-hydrodynamic radius ratio of the analytes.