Biomedical Engineering Reference
In-Depth Information
30
1
R
, 2
R
25
20
1
S
, 2
S
15
10
5
0
-5
-10
0
1
2
3
4
5
(a)
min
1
S
, 2
S
30
20
1
R
, 2
R
10
0
-10
0
1
2
3
4
5
(b)
min
1
S
, 2
S
0
-5
1
R
, 2
R
-10
-15
-20
0
1
2
3
4
5
(c)
min
FIGURE 9.14
Effect of cosurfactant stereochemical coni guration on the enantiomeric
separations of pseudoephedrine. (a)
R
X microemulsion, (b)
RS
microemulsion, and (c)
SS
microemulsion. Peak identii cation: 1
S
,2
S
= (1
S
,2
S
)-pseudoephedrine; 1
R
,2
R
= (1
R
,2
R
)-
pseudoephedrine. Surfactant concentration = 2% w/v; cosurfactant concentration = 1.65% v/v;
0.5% v/v ethyl acetate; 50 mM phosphate buffer, pH 7.0; detection wavelength = 215
5 nm;
capillary dimensions:
L
tot
= 32 cm,
L
eff
= 23.6 cm, i.d. = 50 μm; hydrodynamic injection =
25 mbar for 2 s; applied voltage = 11.5 kV. (From Kahle, K.A. and Foley, J.P.,
Electrophoresis
,
27, 896, 2006. With permission.)
±
and dibutyl-d-tartrate, respectively, 1.23% v/v) were employed for the separation
of six pairs of pharmaceutical enantiomers and results were statistically evaluated.
In comparison to ethyl acetate, dibutyl tartrate proved to be slightly more difi cult to
use due to its higher hydrophobicity. It required longer sonication times for solubili-
zation (microemulsions remained stable after formation for several months) and more
rigorous column conditioning for stable baselines. Another observation was that one
chiral analyte, atenolol that could be minimally resolved with ethyl acetate could
not be resolved at all with the new oil. Enantioselectivity trends were mainly analyte
specii c but overall the system comprised of
R
-DDCV and
S
-dibutyl tartrate gave
the highest value and dual-chirality aggregates provided slight improvements over
single-chirality nanodroplets. The ephedrine derivatives displayed an enantioselec-
tive preference for the surfactant and the oil being present in opposite stereochemical
Search WWH ::
Custom Search