System for chemical analysis

• US 4,771,629 A
• Filed: 03/10/1987
• Issued: 09/20/1988
• Est. Priority Date: 09/17/1985
• Status: Expired due to Fees

• Current Assignee: Rosemount Analytical, Inc. (Emerson Electric Company)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Ryan, Frederick M., Carlson, Gerald L.
• Primary Examiner(s): Chapman, John
• Assistant Examiner(s): WILLIAMS, HEZRON
• Application Number:
  US07/024,297
• Time in Patent Office: 560 Days
• Field of Search: 250/338, 250/339, 250/343, 350/372, 73/23.1, 73/24, 73/61.1 C
• US Class Current: 73/23.35
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/1256 using acousto-optic tunable filter; acousto-optic elements or systems G02F1/11, G02F1/33
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 21/35 using infrared light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 21/3577 for analysing liquids, e.g. polluted water
• CPC Class Codes: G01N 2201/08 Optical fibres; light guides

Abstract

An improved system for quantitative chemical analysis incorporates a chromatographic column. A radiation source of a predetermined range of wavelengths is in optical communication with an emerging specie from the chromatographic column by of a first optical path whereby radiation is modified by characteristic of the specie. A detector is in optical communication with the emerging specie by a second optical path whereby a first output signal reflective of the detected radiation is generated. An acousto-optic tunable filter system is disposed in one of either the first or second optical paths. The radiation is passed through the crystal at a predetermined angle relative to the crystal'"'"'s optic axis. An acoustic transducer is coupled to the crystal to launch acoustic waves into the crystal to interact with a selected narrow bandwidth portion of the radiation to make it distinguishable from the remaining radiation. A computer to which the detector output signal is applied determines the emerging specie by the identifiable characteristics. An auxiliary detector responsive to the emerging specie can be associated with the chromatographic column. A parallel optical path can also be included to define a reference cell. A second output signal reflective of the detected radiation passing through the parallel optical path is generated. The difference between the first and second output signals represents a measure of the emerging specie'"'"'s absorption characteristic. In an alternative embodiment, an acoustooptic dispersive light filter can be inserted in the system.

Claims

1. An improved system for quantitative chemical analysis comprising:

a chromatographic column means into which a mixture is introduced and through which individual specie of the mixture diffuse at various rates so that each single emerging specie is temporally separated from each other specie and has identifiable characteristics;

a radiation source of a predetermined range of wave-lengths in optical communication with the single emerging specie by means of a first optical path whereby radiation from said radiation source is modified by the identifiable characteristics;

a detection means disposed in optical communication with the single emerging specie by means of a second optical path whereby the modified radiation is detected and a first output signal reflective of the detected radiation is generated;

an acousto-optic tunable filter system, which system comprises an acousto-optic tunable filter having an optically aligned acousto-optic crystal disposed in one of said first or second optical paths so as to be in optical alignment therewith such that the radiation is passed through the crystal at a predetermined angle relative to the crystal'"'"'s optic axis, an acoustic transducer means coupled to a variable frequency RF energy source and to the crystal to launch acoustic waves into the crystal to interact with a selected narrow bandwidth portion of the radiation to make it distinguishable from the remaining radiation which selected narrow bandwidth portion is a function of the frequency of the RF energy and the acoustic waves;

computing means to which the detection means output signal is applied for determining the emerging specie by the identifiable characteristics; and

,

a parallel optical path defining thereby a reference cell means whereby radiation passes through both the first and second optical paths and said parallel optical path to the detection means whereby a second output signal reflective of the detected radiation passing through said parallel optical path is generated and wherein the acousto-optic crystal is also disposed in said parallel optical path.

2. The improved system for quantitative chemical analysis according to claim 1 wherein the acousto-optic tunable filter crystal is crystalline quartz (SiO2).

3. The improved system for quantitative chemical analysis according to claim 1 wherein the acousto-optic tunable filter crystal is thallium arsenic selenide (TAS).

4. The improved system for quantitative chemical analysis according to claim 1 wherein the acousto-optic tunable filter crystal is tellurium dioxide (TeO2).

5. The improved system for quantitative chemical analysis according to claim 1 wherein the first and second optical paths comprise optical fiber means.

6. The improved system for quantitative chemical analysis according to claim 1 wherein the first and second optical paths are defined by means including lens means, mirror means, and beam splitter means.

7. The improved system for quantitative chemical analysis according to claim 1 wherein the aotf is disposed in the first optical path.

8. The improved system for quantitative chemical analysis according to claim 1 wherein the aotf is disposed in the second optical path.

9. The improved system for quantitative chemical analysis according to claim 1 including an auxiliary detector means responsive to the emerging specie and in fluid communication with the chromatographic column means.

10. The improved system for quantitative chemical analysis according to claim 1 wherein the computing means is also responsive to the second output signal and wherein the difference between the first and second optical represents a measure of the emerging specie'"'"'s absorption characteristic.

11. The improved system for quantitative chemical analysis according to claim 1 including an auxiliary detector means responsive to the emerging specie and in fluid communication with the chromatographic column means.

12. The improved system for quantitative chemical analysis according to claim 1 wherein the aotf is disposed in the first optical path.

13. The improved system for quantitative chemical analysis according to claim 1 wherein the aotf is disposed in the second optical path.

14. The improved system for quantitative chemical analysis according to claim 1 wherein the acoustooptic tunable filter crystal is crystalline quartz (SiO2).

15. The improved system for quantitative chemical analysis according to claim 1 wherein the acousto-optic tunable filter crystal is thallium arsenic selenide (TAS).

16. The improved system for quantitative chemical analysis according to claim 1 wherein the acoustooptic tunable filter crystal is tellurium dioxide (TeO2).

17. An improved system for quantitative chemical analysis comprising:

a chromatographic column means into which a mixture is introduced and through which individual specie of the mixture diffuse at various rates so that each single emerging specie is temporally separated from each other specie and has identifiable characteristics;

a radiation source of a predetermined range of wavelengths in optical communication with the single emerging specie by means of a first optical path whereby radiation from said radiation source is modified by the identifiable characteristics;

a detection means disposed in optical communication with the single emerging specie by means of a second optical path whereby the modified radiation is detected and a first output signal reflective of the detected radiation is generated;

an acousto-optic tunable filter system, which system comprises an acousto-optic tunable filter having an optically aligned acousto-optic crystal disposed in said first optical path so as to be in optical alignment therewith such that the radiation is passed through the crystal at a predetermined angle relative to the crystal'"'"'s optic axis, an acoustic transducer means coupled to a variable frequency RF energy source and to the crystal to launch acoustic waves into the crystal to interact with a selected narrow bandwidth portion of the radiation to make it distinguishable from the remaining radiation which selected narrow bandwidth portion is a function of the frequency of the RF energy and the acoustic waves;

a parallel optical path defining thereby a reference cell means whereby radiation passes through both the first and second optical paths and said parallel optical path to the detection means whereby a second output signal reflective of the detected radiation passing through said parallel optical path is generated and wherein the acousto-optic crystal is also disposed in said parallel optical path; and

computing means to which the detection means output signal is applied for determining the emerging specie by the identifiable characteristics and said computing means also being responsive to the second output signal and wherein the difference between the first and second optical represents a measure of the emerging specie'"'"'s absorption characteristic.

18. The improved system for quantitative chemical analysis according to claim 17 including an auxiliary detector means responsive to the emerging specie and in fluid communication with the chromatographic column means.

19. The improved system for quantitative chemical analysis according to claim 17 wherein the acousto-optic tunable filter crystal is crystalline quartz (SiO2).

20. The improved system for quantitative chemical analysis according to claim 17 wherein the acoustooptic tunable filter crystal is thallium arsenic selenide (TAS).

21. The improved system for quantitative chemical analysis according to claim 17 wherein the acousto-optic tunable filter crystal is tellurium dioxide (TeO2).

22. The improved system for quantitative chemical analysis according to claim 17 wherein the first and second optical paths comprise optical fiber means.

23. The improved system for quantitative chemical analysis according to claim 17 wherein the first and second optical paths are defined by means including lens means, mirror means, and beam splitter means.

24. An improved system for quantitative chemical analysis comprising:

a chromatographic column means into which a mixture is introduced and through which individual specie of the mixture diffuse at various rates so that each single emerging specie is temporally separated from each other specie and has identifiable characteristics;

a radiation source of a predetermined range of wavelengths in optical communication with the single emerging specie by means of a first optical path whereby radiation from said radiation source is modified by the identifiable characteristics;

a detection means disposed in optical communication with the single emerging specie by means of a second optical path whereby the modified radiation is detected and a first output signal reflective of the detected radiation is generated;

an acousto-optic tunable filter system, which system comprises an acousto-optic tunable filter having an optically aligned acousto-optic crystal disposed in said second optical path so as to be in optical alignment therewith such that the radiation is passed through the crystal at a predetermined angle relative to the crystal'"'"'s optic axis, an acoustic transducer means coupled to a variable frequency RF energy source and to the crystal to launch acoustic waves into the crystal to interact with a selected narrow bandwidth portion of the radiation to make it distinguishable from the remaining radiation which selected narrow bandwidth portion is a function of the frequency of the RF energy and the acoustic waves;

a parallel optical path defining thereby a reference cell means whereby radiation passes through both the first and second optical paths and said parallel optical path to the detection means whereby a second output signal reflective of the detected radiation passing through said parallel optical path is generated and wherein the acousto-optic crystal is also disposed in said parallel optical path; and

computing means to which the detection means output signal is applied for determining the emerging specie by the identifiable characteristics, said computing means also being responsive to the second output signal and wherein the difference between the first and second optical represents a measure of the emerging specie'"'"'s absorption characteristic.

25. The improved system for quantitative chemical analysis according to claim 24 including an auxiliary detector means responsive to the emerging specie and in fluid communication with the chromatographic column means.

26. The improved system for quantitative chemical analysis according to claim 24 wherein the acoustooptic tunable filter crystal is crystalline quartz (SiO2).

27. The improved system for quantitative chemical analysis according to claim 24 wherein the acoustooptic tunable filter crystal is thallium arsenic selenide (TAS).

28. The improved system for quantitative chemical analysis according to claim 24 wherein the acoustooptic tunable filter crystal is tellurium dioxide (TeO2).

29. The improved system for quantitative chemical analysis according to claim 24 wherein the first and second optical paths comprise optical fiber means.

30. The improved system for quantitative chemical analysis according to claim 24 wherein the first and second optical paths are defined by means including lens means, mirror means, and beam splitter means.

31. An improved system for quantitative chemical analysis comprising:

a chromatographic column means into which a mixture is introduced and through which individual specie of the mixture diffuse at various rates so that each single emerging specie is temporally separated from each other specie and has identifiable characteristics;

a radiation source of a predetermined range of wavelengths in optical communication with the single emerging specie by means of a first optical path whereby radiation from said radiation source is modified by the identifiable characteristics;

a detection means disposed in optical communication with the single emerging specie by means of a second optical path whereby the modified radiation is detected and a first output signal reflective of the detected radiation is generated;

an acousto-optic dispersive light filter (AODLF) system, which system comprises an optically birefringenet crystal having an optical input face, and an optical output face, the input face being disposed at a predetermined angle which is normal to the incident radiation in one of said first or second optical paths, an acoustic transducer means coupled to a variable frequency RF energy source and to the crystal to launch acoustic waves into the crystal at a predetermined fixed frequency wherein each wavelength resolution element which emerges from the optical output face is at a different diffracted angle, and wherein the predetermined angle of the optica input face is selected such that for the fixed acoustic frequency, there is a minimum in the Bragg angle with frequency, while the diffracted Bragg angle increases linearly with frequency;

computing means to which the detection means output signal is applied for determining the emerging specie by the identifiable characteristics; and

,

a parallel optical path defining thereby a reference cell means whereby radiation passes through both the first and second optical paths and said parallel optical path to the detection means whereby a second output signal reflective of the detected radiation passing through said parallel optical path is generated and wherein the acousto-optic crystal is also disposed in said parallel optical path.

32. The improved system for quantitative chemical analysis according to claim 31 wherein the computing means is also responsive to the second output signal and wherein the difference between the first and second optical represents a measure of the emerging specie'"'"'s absorption characteristic.

33. The improved system for quantitative chemical analysis according to claim 31 including an auxiliary detector means responsive to the emerging specie and in fluid communication with the chromatographic column means.