Chemistry Reference
In-Depth Information
crystallization analysis. The sample at a
concentration of 0.8% w/v was dissolved
in a 10 ml vial at the autosampler and 0.1 ml
solution was injected into the column. The
crystallization rate was 0.5
8
C/min. The crystal-
lization flow calculated by Equation (2),
according to the column interstitial volume,
was 0.01 ml/min. Once the crystallization
ends, the flow is stopped and the oven goes
in a fast ramp up to 150
reduce analysis time for applications in high
throughput screening of catalyst formula-
tions. The CEF analysis of a complex
polyolefin, Elite
TM
(trademark of the Dow
Chemical Company) is shown in Figure 4
with a total analysis time of 23 minutes. The
analysis was performed at very fast crystal-
lization and heating rates (10
C/min), and
still the separation of the three components
of this resin is reasonably good as shown by
the infrared transmission plot in Figure 4
and the final calculated composition dis-
tribution in Figure 5.
The capabilities of the CEF technique for
high throughput screening were tested
analyzing automatically the same sample in
10 different vial preparations every half an
hour at a crystallization rate of 5
8
C/min and
heating rate of 10
8
C, staying for ten
minutes to ensure full dissolution of the
components previously crystallized in the
column. After that time, the elution flow
begins at 0.1 ml/min to elute the two
metallocene resins separated into the
column as shown in Figure 3. When the
same experiment was repeated without any
crystallization flow, only one peak is
obtained.
8
C/min. The samples were
previously dissolved at 150
8
C for 30 minutes
with gentle shaking in the autosampler. The
results presented in Figure 6 show the good
repeatability of the CEF analysis.
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Crystallization Elution Fractionation
Most work done with crystallization elution
fractionation so far has been directed to
Figure 4.
CEF analysis of an Elite
TM
resin performed at fast crystallization and heating rates of 10
C/min. The top diagram
shows the elution infrared transmission curve. The bottom diagram is the crystallization and elution
temperature profile.
8
