Yokogawa GC1000 Mark II Process Gas Chromatograph - Manual (Page 19)

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<Toc> <Ind> <1. Principle of Gas Chromatograph >
IM 11B03A03-01E 3rd Edition : Aug. 23. 2006-00
(2)Flame Ionization Detector (FID)
The FID utilizes the phenomenon that carbon molecules in the measured component
(hydrocarbon) are ionized in a hot hydrogen flame. That is, it detects the ionization current
which flows between electrodes to which a high voltage is applied. The ionization current is
proportional to the concentration of the measured component.
The FID is used to measure the component concentration of gases containing low concen-
trations of hydrocarbons.
F0104.EPS
Output
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+
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+
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+
+
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Ion collector coil
Hydrogen flame
Jet pipe (nozzle)
Carrier gas
+
Sampling gas
Hydrogen gas for combustion
Figure 1.4 Fundamental Principle of Flame Ionization Detector
(3)Flame Photometric Detector (FPD)
Figure 1.5 shows the structure of the FPD. As the sample gas containing a sulfur compo-
nent is led into the excess hydrogen flame, the component containing the sulfur atoms is
excited. The FPD detects the luminous intensity of the light emitted when this excited
component return to its base state using multiplier phototube and converts it to a voltage.
This voltage represents the concentration of the sulfur component in the measured gas.
The FPD can measure on the sulfur component with a high sensitivity of 1 ppm.
F0105.EPS
Photomultiplier tube
Hydrogen flame
Jet pipe (nozzle)
Carrier gas
+
Sampling gas
Air fo combustion
Hydrogen gas for combustion Hydrogen gas
for combustion
Figure 1.5 Basic Configuration of Flame Photometric Detector