Chemically L-phenylalaninamide-modified monolithic silica column prepared by a sol-gel process far enantioseparation of dansyl amino acids by ligand exchange-capillary electrochromatography
Zl. Chen et T. Hobo, Chemically L-phenylalaninamide-modified monolithic silica column prepared by a sol-gel process far enantioseparation of dansyl amino acids by ligand exchange-capillary electrochromatography, ANALYT CHEM, 73(14), 2001, pp. 3348-3357
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.