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Gas Analysis System using Full Vacuum Type FT/IR
(Trace amount of H2O in N2 gas)
(1/2)
No. 230TR0187-E
The analysis of low concentration gases using long pathlength gas cells has been reported previously, however, it can be difficult
to accurately quantitate gases at low concentrations when the absorption peaks of the target gas overlap with the peaks of
atmospheric water vapor or, when the target gas itself is H2O or CO2, which are presnet in the atmosphere. This is because even
with a vacuum FT-IR instrument, it was not possible to evacuate the sample chamber with the long pathlength cell present. The full
vacuum gas analysis system introduced in this application note has a special gas cell integrated into the sample chamber, allowing
the entire light path to remain under full vacuum with the gas cell in place. This full vacuum model makes it possible to quantitate
concentrations of H2O even at the 0.1 ppm level.
For the measurement, there are separate vacuum lines for evacuation of the FT-IR instrument and the gas cell, with independent
evacuation capability for the separate components. Adding a vacuum gauge to the gas cell makes it possible to control extremely
方案详情
Application NoteNo.230TR0187-E No. 230TR0187-E Gas Analysis System using Full Vacuum Type FT/IR(Trace amount of H20 in N2 gas) Introduction The analysis of low concentration gases using long pathlength gas cells has been reported previously， however， it can be difficultto accurately quantitate gases at low concentrations when the absorption peaks of the target gas overlap with the peaks ofatmospheric water vapor or， when the target gas itself is H，0 or CO， which are presnet in the atmosphere. This is because evenac1111with a vacuum FT-IR instrument， it was not possible to evacuate the sample chamber with the long pathlength cell present. The fullvacuum gas analysis system introduced in this application note has a special gas cell integrated into the sample chamber， allowingthe entire light path to remain under full vacuum with the gas cell in place. This full vacuum model makes it possible to quantitateconcentrations of H，O even at the 0.1 ppm level. Instrument and Measurement For the measurement， there are separate vacuum lines for evacuation of the FT-IR instrument and the gas cell. with independentevacuation capability for the separate components. low concentrations of the gas samples. Cell specification Cell type：Multi-pass ‘White’cellPathlength ：10 metersCell body：Stainless steelMirror material：Stainless steelMirror surface：Gold coatedO-ring ：VitonWindow：CaF2Heating：Possible， max. 100℃Cell capacity：Approx. 2 LGas in/output port：1/4 inch VCR Fig. 1 Full vacuum type FT-IR gas analysis system (10 meter cell) Measurement example The quantitation of a trace amount of water vapor (H，O) within nitrogen gas was attempted. Water vapor with a concentrationof 100 ppm was diluted by monitoring the pressure gauge during dilution of the standard samples with concentrations of 0.0， 0.51，1.02 and 2.48 ppm. Figure 2 shows the IR spectra of water vapor for each concentration. For the 0 ppm concentration， there wasno absorption due to water vapor observed in the spectrum. The calibration curve in Figure 3 was created using the absorptionpeak at 1653 cm. Easton， Maryland 21601 Fig.2 Expanded region for spectra of low concentration H，0 Condition Fig. 3 H，O calibration curve Easton， Maryland 21601 JASCO，USACommerce Drive
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