C. Desiderio et al., Use of vancomycin silica stationary phase in packed capillary electrochromatography I. Enantiomer separation of basic compounds, ELECTROPHOR, 22(3), 2001, pp. 535-543
Chiral separation of basic compounds was achieved by using 75 or 100 mum ID
fused-silica capillaries packed with a vancomycin-modified diol silica sta
tionary phase. The capillary was firstly packed for about 12 cm with a slur
ry mixture composed of diolsilica (3:1) then with the vancomycin modified d
iol-silica (3:1) (23 cm), and finally with diol-silica (3:1) for about 2 cm
. Frits were prepared by a heating wire at the two ends of the capillary; t
he detector window was prepared at 8.5 cm from the end of the capillary whe
re vancomycin was not present. The influence of the mobile phase compositio
n (pH and concentration, organic modifier type and concentration) on the ve
locity of the electroosmotic flow, chiral resolution and enantioselectivity
was studied. Good enantiomeric resolution was achieved for atenolol, oxpre
nolol, propranolol, and venlafaxine using a mobile phase composition of 100
mM ammonium acetate solution (pH 6)/water/acetonitrile (5:5:90 v/v/v) whil
e for terbutaline a mixture of 5:15:80 v/v/v provided the best separations.
The use of methanol instead of acetonitrile caused a general increase of e
nantiomer resolution of the studied compounds together with a reduction of
efficiency and detector response. However, the combination of acetonitrile
and methanol in the mobile phase las, e.g., 10% methanol and 80% acetonitri
le) allowed to improve the enantiomer resolution with satisfactory detector
response.