FTIR spectrometer with cut-off filter for hydrogen sulfide detection
A gas analysis system with an FTIR spectrometer preferably utilizes a long path gas cell, a narrow band detector, and an optical filter that narrows the detection region to measure hydrogen sulfide.
1. A Fourier transform infrared spectrometry system for measuring hydrogen sulfide, comprising:
a source for generating light;
an interferometer for receiving the light;
a sample cell containing a gas sample;
a detector for detecting the light from the interferometer and after passing through the sample gas;
a bandpass filter for filtering light prior to being detected the detector including 3,700 cm −1 or 2,700 cm −1 ; and
a controller for detecting an output of the detector as the interferometer is scanned and processes interferograms to measure a concentration of the hydrogen sulfide in the sample cell.
2. The system of claim 1 , wherein the detector is an MCT detector.
3. The system of claim 1 , wherein the detector has at least an 8 μm cutoff.
4. The system of claim 1 , wherein the detector has at least a 5 μm cutoff.
5. The system of claim 1 , wherein the optical filter has a bandpass of less than 300 cm −1 .
6. The system of claim 1 , wherein the optical filter has a bandpass of less than 100 cm −1 .
7. The system of claim 1 , wherein the controller processes the interferograms within the bandpass of the bandpass filter at two resolutions and using the interferograms processed at a lower resolution as a background for interferograms processed at a higher resolution.
8. The system of claim 7 , wherein the controller employs cosine apodization.
9. The system of claim 7 , wherein the controller adds a filter spectrum of the filter into a regression analysis.
10. The system of claim 1 , further comprising the controller operating a pump pressurizing the gas sample in the sample cell.
11. A spectrometry method, comprising:
analyzing a gas sample with a Fourier transform infrared spectrometer;
detecting the light after passing through the sample gas with a detector; and
filtering light prior to being detected to include 3,700 cm −1 or 2,700 cm −1 to measure hydrogen sulfide; and
detecting an output of the detector as an interferometer of the Fourier transform infrared spectrometer is scanned and processing interferograms to measure a concentration of the hydrogen sulfide in the gas sample.
12. The method of claim 11 , wherein the detector is an MCT detector.
13. The method of claim 11 , wherein the detector has at least an 8 μm cutoff.
14. The method of claim 11 , wherein the detector has at least a 5 μm cutoff.
15. The method of claim 11 , further comprising filtering the light with a bandpass of less than 300 cm −1 .
16. The method of claim 11 , further comprising filtering the light with a bandpass of less than 100 cm −1 .
17. The method of claim 11 , further comprising processing the interferograms at two resolutions and using the interferograms processed at a lower resolution as a background for interferograms processed at a higher resolution.
18. The method of claim 17 , further comprising employing cosine apodization to filter the interferograms.
19. The method of claim 17 , further comprising adding a filter spectrum of the filter into a regression analysis.
20. The method of claim 11 , further comprising pressurizing the gas sample in the sample cell.