Use of vancomycin silica stationary phase in packed capillary electrochromatography: III. Enantiomeric separation of basic compounds with the polar organic mobile phase

The separation of basic compounds in their enantiomers was achieved by using capillary electrochromatography in 50 or 75 micron ID fused silica capillary packed with silica stationary phase derivatized with vancomycin and mobile phases composed by mixtures of polar organic solvents containing 13 mM of ammonium acetate. Enantiomer resolution, electroosmotic flow, number of theoretical plates was strongly influenced by the type and concentration of the organic solvent. Mobile phases composed by 13 mM ammonium acetate dissolved in mixtures of acetonitrile/methanol or ethanol or n-propanol or iso-propanol were tested and the highest enantioresolutions were achieved using the first mobile phase allowing the separation of almost all investigated enantiomers (9 over 11 basic compounds). The use of capillaries with different ID (50 and 75 micron I.D.) packed with the same chiral stationary phase revealed that higher number of theoretical plates and higher enantioresolution was achieved with the tube with lowest ID.