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Detector Systems
Thermal conductivity detector (TCD)
145
Because of its exceptionally high thermal conductivity and chemical
inertness, He is the recommended carrier gas: it gives large thermal
conductivity differences with all compounds except H
(considerations
necessary in H
analyses are discussed later). With He as carrier, the
TCD exhibits universal response. For propane, the sensitivity limit is
about 400 picograms/ml of He carrier gas.
The TCD exists in two configurations: either its exhaust vent tube exits
at the top of the detector or the exhaust vent tube returns to the inside of
the oven for connection to an FID or other device.
Reference
Gas
Capillary
Makeup
Gas
Traps
Final Pressure Regulators
and Gauges
External
Plumbing
Internal
Plumbing
Flow Manifold Block
On/Off
MAKEUP GAS
On/Off
REFERENCE
Column
Makeup Gas Adapter:
Capillary Columns Only
Detector
Filament
Electronics
Solenoid Switching
Valve
From
Inlet
Makeup Gas
Reference
Flow Diagram, Thermal Conductivity Detector (TCD)
Figure 7-8