Chiral Separation by Capillary Electrophoresis in Nonaqueous Medium

In the last few years, nonaqueous background electrolyte (BGE) solutions have attracted increasing interest, not only in capillary zone electrophoresis (CZE) but also in other capillary electrophoretic techniques (CE) (1 ). Nonaqueous capillary electrophoresis (NACE) exploits the vastly different physicochemical properties of organic solvents. With mere adjustment of BGE composition, parameters such as resolution, analysis time, and selectivity can be fine-tuned or even altered dramatically (2 –9 ). The solubility of the analytes and additives can be enhanced, and the possible adsorption of the analytes on the capillary wall can be reduced. Because solvation of the analytes differs considerably from that in aqueous solutions, a strong effect on the separation selectivity can be seen. In addition, low currents make the use of higher electric field strengths possible in separations. The interactions, which hardly take place in water, can be utilized in nonaqueous solvents permitting capillary electrophoretic separation of even uncharged compounds after the formation of complexes with ionic additives (6 ,10 ). Moreover, the solutes labile in aqueous solutions can be stable in nonaqueous media.