Infrared emission detection of a gas

• US 5,473,162 A
• Filed: 09/20/1993
• Issued: 12/05/1995
• Est. Priority Date: 10/26/1987
• Status: Expired due to Fees

• Current Assignee: Baylor University
• Original Assignee: Baylor University
• Inventors: Srinivasan, Ravishankar, Kubala, Sidney W. Jr., Hudson, M. Keith, Zhand, Yunke, Lam, Christopher K. Y., Tilotta, David C., Busch, Kenneth W., Busch, Marianna A.
• Primary Examiner(s): FIELDS, CAROLYN
• Application Number:
  US08/123,733
• Time in Patent Office: 806 Days
• Field of Search: 356/311, 356/312, 356/313, 356/314, 250/339.13, 250/339.14, 250/341.6, 250/339.08
• US Class Current: 250/341.6
• CPC Class Codes: G01N 2021/3125 Measuring the absorption by excited molecules
• CPC Class Codes: G01N 2021/3595 using FTIR
• CPC Class Codes: G01N 21/71 thermally excited
• CPC Class Codes: G01N 21/72 using flame burners
• CPC Class Codes: G01N 30/74 Optical detectors measurement of intensity, velocity, spectral content, polarisation, or phase of infrared, visible or ultraviolet light G01J

Abstract

Apparatus and method for qualitatively and quantitatively analyzing infrared emission from excited molecules in the determination of, for example, total inorganic carbon, chloride and available chlorine in aqueous samples. Methods of exciting the gas-phase, infrared-active molecules to emit radiation include flame excitation, furnace excitation, excitation by electron impact in a gas discharge or excitation by collisions with a vibrationally excited diatomic molecule. The detector is optimized by use of dual beam system with background subtraction capabilities thereby eliminating background noise and fluctuations therein.

Claims

1. An apparatus for detecting and making quantitative measurements of at least one selected component in a sample, in which at least one selected component of the sample, or at least one selected substance produced from the at least one selected component in the sample and characteristic of the at least one selected component, is introduced into an exciting means, and when the at least one selected component is present in the sample, gas-phase infrared-active molecules emit infrared radiation at at least one characteristic wavelength in proportion to the quantity of the at least one selected component in the sample, comprising:

means for exciting the gas-phase, infrared-active molecules to emit radiation over a given path, wherein when the at least one selected component is present in the sample, the gas-phase infrared-active molecules emit radiation at the at least one characteristic wavelength with an intensity proportional to the quantity of the at least one selected component in the sample and wherein the means for exciting the gas-phase, infrared-active molecules is by furnace excitation, excitation by electron impact in a gas discharge or excitation by collisions with a vibrationally excited diatomic molecule;

infrared discriminating and detector means located on said given path for detecting infrared radiation at the at least one characteristic wavelength and for generating an output signal representative thereof, and thereby determining the quantity of the at least one selected component in the sample.

2. The apparatus according to claim 1, wherein said infrared discriminating and detector means includes wavelength discriminating means located on said path, between the exciting means and the infrared detector means, for allowing the at least one characteristic wavelength to pass from the exciting means to the detector means while inhibiting the passage of other wavelengths.

3. The apparatus according to claim 1, wherein said infrared discriminating and detector means includes means for separating the wavelengths of the emitted radiation into an infrared spectrum.

4. The apparatus according to claim 1, wherein said infrared discriminating and detector means includes a monochromator.

5. The apparatus according to claim 1, further including a computer means, responsive to an output signal from the infrared detector means, for performing signal processing thereon to provide an output indicative of the quantity of the at least one selected component present in the sample.

6. The apparatus according to claim 1, wherein said infrared discriminating and detector means includes an interferometer.

7. The apparatus according to claim 6, further comprising a computer means, coupled to the interferometer, for performing a Fourier transform analysis on an output signal from the interferometer to thereby obtain a spectral analysis characteristic of the sample.

8. The apparatus according to claim 1, further including vaporizing means for vaporizing a liquid sample and for conducting the resultant vapors into said exciting means.

9. The apparatus according to claim 1, wherein the means for exciting the gas-phase, infrared-active molecules is by furnace excitation.

10. The apparatus according to claim 1, wherein said infrared detector means includes a thermal infrared detector.

11. The apparatus according to claim 1, wherein said infrared detector means includes a quantum detector.

12. The apparatus according to claim 1, wherein the at least one selected component or the at least one selected substance contains carbonates or calcinates, further including means for acidifying the at least one selected component or the at least one selected substance to generate CO₂ therefrom, wherein the CO₂ so generated is introduced into the exciting means.

13. The apparatus according to claim 1, wherein the at least one selected component or the at least one selected substance contains carbon-containing compounds, further including means for oxidizing the at least one selected component or the at least one selected substance to generate CO₂ therefrom, wherein the CO₂ so generated is introduced into the exciting means.

14. The apparatus according to claim 1, wherein the at least one selected component or the at least one selected substance contains hypochlorous acid or hypochlorite ions, further including means for acidifying the at least one selected component or the at least one selected substance with HCl to generate Cl₂ therefrom, wherein the Cl₂ so generated is introduced into the exciting means.

15. The apparatus according to claim 1, wherein the at least one selected component or the at least one selected substance contains chloride ions, further including means for oxidizing and acidifying the at least one selected component or the at least one selected substance to generate chlorine Cl₂ therefrom, wherein the Cl₂ so generated is introduced into the exciting means.

16. The apparatus according to claim 1, wherein the at least one selected component of the sample or the at least one selected substance includes carbon-containing compounds, and said exciting means includes a means for oxidizing the at least one selected component of the sample or the at least one selected substance to generate CO₂ therefrom, wherein the CO₂ so generated is introduced into the exciting means.

17. The apparatus according to claim 1, wherein the at least one selected component or the at least one selected substance includes chlorine-containing organic compounds, and said exciting means includes a means for combusting the at least one selected component or the at least one selected substance to thereby generate HCl therefrom, wherein the HCl so generated is introduced into the exciting means.

18. The apparatus according to claim 1, wherein the at least one selected component or the at least one selected substance includes fluorine-containing organic compounds, and said exciting means includes a means for combusting the at least one selected component or the at least one selected substance to thereby generate HF therefrom, wherein the HF so generated is introduced into the exciting means.

19. A method for detecting and making quantitative measurements of at least one selected component in a sample, in which at least one selected component of the sample, or at least one selected substance produced from the at least one selected component in the sample and characteristic of the at least one selected component, is introduced into an exciting means, and when the at least one selected component is present in the sample, gas-phase infrared-active molecules emit infrared radiation at at least one characteristic wavelength in proportion to the quantity of the at least one selected component in the sample, comprising the steps of:

exciting the gas-phase, infrared-active molecules to emit radiation, wherein when the at least one selected component is present in the sample, the gas-phase infrared-active molecule emit radiation at the at least one characteristic wavelength with an intensity proportional to the quantity of the at least one selected component in the sample; and

selectively detecting infrared radiation emitted at the at least one characteristic wavelength and generating an output signal representative thereof, and thereby determining the quantity of the at least one selected component in the sample and wherein said exciting step is by thermal excitation using an electric furnace, excitation by electron impact in a gas discharge or excitation by collisions with a vibrationally excited diatomic molecule.

20. The method according to claim 19, including the step of discriminating the at least one characteristic wavelength by allowing only the at least one characteristic wavelength to be detected in the detecting step while inhibiting the detection of other wavelengths.

21. The method according to claim 20, wherein said discriminating step includes separating the wavelengths of the emitted radiation into an infrared spectrum.

22. The method according to claim 20, wherein said discriminating step includes utilizing a monochromator.

23. The method according to claim 20, wherein said discriminating step includes utilizing an interferometer.

24. The method according to claim 23, wherein said discriminating step includes utilizing a computer coupled to the interferometer for performing a Fourier transform analysis on an output signal from the interferometer to thereby obtain a spectral analysis characteristic of the sample.

25. The method according to claim 19, further including utilizing a computer for performing signal processing on the output signal produced by said detecting step to provide an output indicative of the quantity of the at least one selected component present in the sample.

26. The method according to claim 19, including vaporizing a liquid sample and utilizing the resultant vapors in said exciting step.

27. The method according to claim 19, wherein said exciting step is by thermal excitation using an electric furnace.

28. The method according to claim 19, wherein the at least one selected component or the at least one selected substance contains carbonates or calcinates, further including acidifying the at least one selected component or the at least one selected substance to generate CO₂ therefrom, and utilizing the CO₂ so generated in the exciting step.

29. A method according to claim 19, wherein the at least one selected component or the at least one selected substance contains carbon-containing compounds, further including oxidizing the at least one selected component or the at least one selected substance to generate CO₂ therefrom, and utilizing the CO₂ so generated in the exciting step.

30. The method according to claim 19, wherein the at least one selected component or the at least one selected substance contains hypochlorous acid or hypochlorite ions, further including acidifying the at least one selected component or the at least one selected substance with HCl to generate Cl₂ therefrom, and utilizing the Cl₂ so generated in the exciting step.

31. The method according to claim 19, wherein the at least one selected component or the at least one selected substance contains chloride ions, further including oxidizing and acidifying the at least one selected component or the at least one selected substance to generate chlorine Cl₂ therefrom, and utilizing the Cl₂ so generated in the exciting step.

32. The method according to claim 19, wherein the at least one selected component of the sample or the at least one selected substance includes carbon-containing compounds and oxidizing the at least one selected component of the sample or the at least one selected substance to generate CO₂ therefrom, and utilizing the CO₂ so generated in the exciting step.

33. The method according to claim 19, wherein the at least one selected component or the at least one selected substance includes chlorine-containing organic compounds and combusting the at least one selected component or the at least one selected substance to generate HCl therefrom, and utilizing the HCl so generated in the exciting step.

34. The method according to claim 19, wherein the at least one selected component or the at least one selected substance includes fluorine-containing organic compounds and combusting the at least one selected component or the at least one selected substance to generate HF therefrom, and utilizing the HF so generated in the exciting step.