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5
Micro GC Channels
Tuning the backflush time
Tuning the backflush time
To set the proper backflush time for each new backflush to detector channel, follow either the
"8 m 5CB BF2D procedure"
8 m 5CB BF2D procedure
Table 23 8 m 5CB BF2D settings
Parameter
Column pressure
Injection temperature
Column temperature
Injection time
Run time
Sample gas
1 Set backflush (BF) time to 0 seconds. Start a run to obtain the peaks of all eluted components.
Record the retention time (RT) of n-pentane and 2,2-dimethylbutane.
2 Set run time to a value which is 10 seconds longer than the RT of 2,2-dimethylbutane. Set BF
time to 5 seconds. Start a run again.
3 Increase BF time by 0.5 seconds steps, and start a run. Observe the peak height of
2,2-dimethylbutane. Continue increasing BF time until the 2,2-dimethylbutane peak is
observed (peak height > 3 µV).
4 Finely tune the BF time, find the data point when the 2,2-dimethylbutane peak is observed.
Decrease BF time by 0.1 seconds steps, and start a run until the peak disappears (peak height
< 3 µV). Set BF time for this channel to that value minus 0.2 seconds. A typical "clean cut" time
range of 8m 5CB BF2D channel is approximately 0.3-0.5 seconds. (See
Figure 32.
8m 5CB Column for natural gas analysis
80
or the
C
6+
"10 m Al2O3/KCl BF2D procedure"
Settings
150 kPa
110 °C
72 °C
40 ms
90 s
NGA gas
on page 81.
Figure
32.)
n-pentane
Agilent 990 Micro GC User Manual
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