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12
MinimumTemperature
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For maximum resolution of chiral
compounds with low boiling points
(below100
°
C), initial temperatures of
35-40
°
Care recommended for theRt-
β
DEXsm,Rt-
β
DEXse,andRt-
β
DEXsa
columns. In contrast, the same vola-
tile compounds exhibit a very broad
peakshapeon theRt-
β
DEXspandRt-
β
DEXcstcolumnsat these initialoven
temperatures. Linalool oxides are
volatile compounds that exhibit peak
broadening andalmost no resolution
on the Rt-
β
DEXcst column with an
initial oven temperature of 40
°
C
(Fig-
ure14A)
. Thepeak shapesandover-
all resolutionof the linalooloxides im-
prove when initial temperature is
increased to70
°
C,even though the in-
dividual enantiomers of both the cis
and trans isomers are not separated
(
Figure 14B
). Higher initial tempera-
turesdonot always completely elimi-
nate peak broadening for some com-
ponents. However, the improvement
in solvent peak shape indicates a
physical transitionof thecyclodextrin
macromolecules from a crystalline
structure to a liquid at this higher
temperature.Thus the recommended
minimum operating temperature of
Rt-
β
DEXspandRt-
β
DEXcst columns
is 60°C.
Figure 14A
Linalool oxides exhibit extreme peak broadening and poor resolution on the
Rt-
β
DEXcst columnwith an initial oven temperature of 40°C.
Figure 14B
Linalool oxides exhibit improved peak shape and resolution on the
Rt-
β
DEXcst columnwhen initial oven temperature is increased to 70°C.
cis& trans linalool oxides
15
min.
20
25
cis& trans linalool oxides
15
min.
20
25
30m, 0.32mm ID, 0.25µmRt-
β
DEXcst (cat.# 13102)
Oven temp.:
70°C (hold 1min.) to 200°C@
2°C/min.;
Carrier gas:
hydrogen; 80cm/sec. set @ 40°C;
Detector:
FID set @ 220°C
30m, 0.32mm ID, 0.25µmRt-
β
DEXcst (cat.# 13102)
Oven temp.:
40°C (hold 1min.) to 200°C@
2°C/min.;
Carrier gas:
hydrogen; 80cm/sec. set @ 40°C;
Detector:
FID set @ 220°C
Higher initial
temperatures do not
always completely elimi-
nate peak broadening
for some components.
However, the improve-
ment in solvent peak
shape indicates a physi-
cal transition of the
cyclodextrinmacromol-
ecules from a crystalline
structure to a liquidat
this higher temperature.
