Detector Systems
Thermal conductivity detector (TCD)
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As Figure 7•9shows, however, the lower the detector zone temperature,
the greater is the temperature difference between the filament versus the
surrounding detector body temperature. Thus, for maximum sensitivity,
the detector zone should be operated at the lowest temperature possible
(limited by highest boiling components condensing inside the detector).
Also, a second advantage is one of increased filament lifetime.
Gas flow rates
After the detector and instrument are allowed time for thermal
stabilization (about 1/2•hourafter the oven and zones achieve desired
setpoint values), two gas flow rates, column and reference gas, must be
set independently.
After setting optimal carrier gas flow rate through the column, Figure
7•10may be used to determine the corresponding optimal reference flow
rate.
60
55
50
45
40
35
0
20
40 60 80 100
Column Flow Rate:
30 ml/min
Column Flow Rate:
60 ml/min
Column Flow Rate:
20 ml/min
Reference Gas Flow Rate
(ml/min)
Relative
Response
TCD Response versus Reference Flow Rate
Figure 7-10
