Chapter': ' TCD Detector ".
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Thermal Conductivities of common gases
As illustrated by the table below, Heliumand Hydrogen have
the highest thermal conductivitiesof any gases. TheTCD de–
tector responds to the difference between the thermal conduc–
tivity of the carrier gas and the analytepeak. The greater the
difference, the better the sensitivity. For this reason, Nitrogen
is only used as a carrier gaswhen hydrogen or heliumis the
target analyte. Argon is sometimes used as a carrier gas, but
would have little sensitivity towards ethane or propane, for ex–
ample, because the thermal conductivity of the argon ( 39 ) is
very close to that of ethane ( 43 ) or propane ( 36 ).
THERMAL CONDUCTIVITIESOF
SOME COMMONGASES
Air
58
Argon 39
CO 53
C02 34
H2
419
HE
343
N2
57
02
58
Neon 109
Methane 73
Ethane 43
Propane 36
Butane 32
