Chemically L-phenylalaninamide-modified monolithic silica column prepared by a sol-gel process far enantioseparation of dansyl amino acids by ligand exchange-capillary electrochromatography

A new type of chiral monolithic column was successfully developed for the e nantioseparation of dansyl amino acids by ligand exchange-capillary electro chromatography (LE-CEC) in this work, The monolithic column matrix was prep ared by a sol-gel process and then chemically modified with the spacer (3-g lycidoxypropyl)trimethoxysilane and the chiral selector L-phenylalaninamide . After being conditioned with Cu(II) aqueous solution, the ligand exchange -chiral stationary phase (LE-CSP) possesses positive charges, When the exte rnal electric field was applied in CEC, electroosmotic flow (EOF) was gener ated on the surface of LE-CSP in the direction from the cathode to the anod e. The EOF was found to be dependent on the applied electric field strength and the composition of the mobile phase. With the increase of pH of the mo bile phase, the EOF showed a tendency to decrease. Scanning electron micros copy showed that the chiral monolithic column has a continuous skeleton and large through-pore structure. The separation efficiency (theoretic plate n umbers) for the separation of Dns-DL-Leu reached up to 9.0 x 10(4) plates m (-1) for the D-enantiomer and 6.6 x 10(4) plates m(-1) for the L-enantiomer , by using pH 5.5, acetonitrile/0.50 mM Cu(Ac)(2)-50 mM NH4Ac (7:3) as mobi le phase, The reproducibility and life-time were satisfactory. CEC was carr ied out with conventional capillary electrophoresis equipment without press urizing the ends of the capillary. No bubble was formed during the operatio n, after degassing the mobile phase and conditioning the column.