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Gas considerations
11
Gases for capillary columns
Hydrogen is the recommended carrier gas for capillary analyses; helium
is an acceptable alternate and nitrogen is least desirable.
These detectors are compatible with packed columns which use higher
carrier gas flow rates than those used with capillary columns. A separate
makeup gas system brings total flow into a detector up to the rate for
optimum sensitivity with capillary columns. For each detector and carrier
gas, there is a preferred choice for makeup gas.
Detector Carrier Gas Preferred Makeup Gas Second Choice/Notes
FID
NPD
ECD
TCD
Hydrogen
Helium
Nitrogen
Hydrogen
Helium
Nitrogen
Hydrogen
Helium
Nitrogen
Argon/Methane
Hydrogen
Helium
Nitrogen
Argon
Nitrogen
”
”
Helium
”
”
Argon/Methane
”
Nitrogen
Argon/Methane
Same as carrier
and reference gas
Helium
”
”
See comment below.
Nitrogen
”
Argon/Methane
Nitrogen
Same as carrier and
reference gas
Gas Recommendations for Capillary Columns
When an NPD is used with an HP Series 530
¿
capillary column,
hydrogen carrier gas, and a packed column inlet (flow•controlled),both
isothermal and temperature programmed analyses may be run.
However, if a capillary inlet (pressure•controlled)is used, only isothermal
analysis is recommended. Temperature programming changes the
resistance of the column and the flow of hydrogen into the detector. NPD
sensitivity is very sensitive to hydrogen flow.
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