Chemistry Reference
In-Depth Information
160
140
120
100
80
0
5
10
15
20
Elution Volume (mL)
Figure 4.
Temperature gradient for the spray nozzle of the LC-Transform interface.
from the fact that the components of the
mobile phase have different boiling points.
In the present case these are 220
To prove that the system is working
properly, a model PP-PE blend was frac-
tionated and analyzed by HPLC-FTIR. The
concentration profile of this separation
obtained by the ELS detector is shown in
Figure 5.A, indicating that a perfect sepa-
ration into two components was obtained.
The first peak eluting at 2 mL corresponds
to PP and the later eluting peak corre-
sponds to PE. The Gram-Schmidt plot
resulting from summarizing all FTIR peak
intensities in the range of 2800-3200 cm
1
as a presentation of the concentration
profile is given in Figure 5.B. The compar-
ison of the Gram-Schmidt plot (Figure 5.B)
with the
C for
TCB and 170
8
C for EGMBE. Therefore,
the evaporation temperature in the LC-
Transform interface has to be changed con-
tinuously and corresponding to the actual
mobile phase composition. A linear tem-
perature gradient for the LC-Transform
nozzle has been found to be the optimum,
see Figure 4. Starting with a nozzle tem-
perature of 90
8
C for 6.5 min, the nozzle
temperature is raised linearly to 151
8
Cin
the following 3 min and than kept constant
for another 3 min. Finally, the nozzle
temperature is decreased back to 90
8
C.
concentration chromatogram
8
A
35
1,0
B
5
A
PE
30
0,8
4
25
PP
0,6
3
20
15
0,4
2
10
0,2
1
5
0
0,0
0
0
2
4
6
8
10
12
0
2
4
6
8
10
Elution Volume (mL)
Elution Volume (mL)
Figure 5.
HT-HPLC separation of a PP-PE blend (A) and HPLC/FTIR analysis (B), full line ELSD trace (A) or Gram-Schmidt plot
(B),
&
relative amount of CH
3
groups (peak ratio CH
3
/CH
2
), chromatographic conditions see Figure 3.
