○
○
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○
○
○
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10
Figure 12B
Faster linear velocities provide maximum
resolution of chiral pairs.
Figure 12A
Higher Trennzahl values are obtained at 40 cm/sec
with hydrogen carrier gas.
Rt-
β
DEXsa:
40°C (80°C for lactones) to 200°C@
2°C/min. (hold 1min.). Hydrogen carrier gas.
Rt-
β
DEXsa:
40°C to 200°C@ 2°C/min. (hold 1min.).
Hydrogen carrier gas.
OPTIMIZATION OF
CHIRAL SEPARATIONS
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
Although the new
β
-cyclodextrin col-
umns can resolve a variety of chiral
compounds,certainparametersmust
be optimized to obtain maximum
separationandcolumnperformance.
Variation in linear velocity and tem-
perature ramp rate can greatly affect
the resolution of enantiomers. De-
pendingon the typeof chiral column,
initialGCoven temperaturecanaffect
peakwidth. Column sample capacity
varieswithdifferent compounds, and
overloading results in broad tailing
peaks and reduced enantiomeric
separation.
LinearVelocity (ColumnFlow)
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
The resolution between the enantio-
meric pairs can be improved by in-
creasing the linearvelocity.This ises-
pecially important if the resolution
factor isbelow two foroptical isomers
(see Table I). Trennzahl values are
measurements of column separation
efficiency, which are often optimum
at a linear velocity of 40 cm/secwith
hydrogen carrier gas. This is illus-
trated in
Figure 12A
. Although opti-
mal linearvelocitycanbedifferent for
each chiral compound and column,
the typicaloptimum linearvelocity for
maximumenantiomericseparation is
around 80 cm/sec with hydrogen
carrier gas, as illustrated with six
chiral compounds on the Rt-
β
DEXsa
column in
Figure 12B
. This is twice
the linear velocity required toachieve
maximum efficiency as indicated by
the Trennzahl values of 1-octen-3-ol
enantiomers in
Figure 12A
.
1-octen-3-ol
linalool
α
-ionone
γ
-nonalactone
γ
-undecalactone
δ
-decalactone
30
40
80
120
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
30
40
80
120
30
25
20
15
10
5
0
Linear Velocity (cm/sec)
Trennzahl Value
Linear Velocity (cm/sec)
Resolution Factor
