US4851683A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Element specific radio frequency discharge helium plasma detector for chromatography
Assignee: Brigham Young University
•
Filing: 1987-03-09
•
Granted: 1989-07-25
•
Expires: 2007-03-09
Abstract
Abstract A method and apparatus for element specific detection in chromatogragphic eluents. The apparatus is comprised of a radio frequency discharge between electrodes in helium, and utilizes a low-resolution plasma emission spectrometer to monitor selected spectral emissions produced when the helium discharge decomposes and excites the atomic constituents in chromatographic column effluents. The spectrometer is tuned to an atomic emission line in the near-infrared portion of the spectrum, and the emission intensity from the discharge region of a selected line is used to monitor the concentration of the element producing that line. Acceptable detector sensitivity is achieved by the use of a high-throughput optical system. Selectivity is achieved by a combination of correct line selection, plasma and carrier gas purification, and plasma gas doping.
Inventors
- 👤 Frank J. Yang
- 👤 Paul B. Farnsworth
- 👤 Karin E. Markides
- 👤 Milton L. Lee
- 👤 Ronald J. Skelton Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:29
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/62; G01N21/71; G01N21/73; G01N30/00; G01N30/02; G01N30/62; G01N30/74
Claims Analysis
Total Claims: 96
Claim 1
Independent Claim
170 words
A detector for detector specific elements in the effluent stream of a chromatograph comprising: a plasma containment chamber having an inlet, an outlet, and a viewing means for exposing a portion of said plasma containment chamber to a monitoring means; sampling means for introducing a sample from the effluent stream of a chromatograph into said plasma containment chamber; plasma means for creating a plasma in said plasma containment chamber, said plasma exciting atomic and molecular components in said sample, thereby creating spectral emissions; monitoring means sensitive to red and infrared radiation for detecting said spectral emissions through said viewing means, said monitoring means comprising a spectrometer having high optical thoughput; and dopant means for introducing a dopant into said plasma in said plasma containment chamber in order to selectively reduce spectral interference from said plasma containment chamber, said dopant comprising a gas of a material for selective combination with molecular species which would otherwise produce interfering emissions in said plasma in the red and infrared regions of the electromagnetic spectrum.
Claim 2
Dependent Claim
170 words
A detector for detector specific elements in the effluent stream of a chromatograph comprising: a plasma containment chamber having an inlet, an outlet, and a viewing means for exposing a portion of said plasma containment chamber to a monitoring means; sampling means for introducing a sample from the effluent stream of a chromatograph into said plasma containment chamber; plasma means for creating a plasma in said plasma containment chamber, said plasma exciting atomic and molecular components in said sample, thereby creating spectral emissions; monitoring means sensitive to red and infrared radiation for detecting said spectral emissions through said viewing means, said monitoring means comprising a spectrometer having high optical thoughput; and dopant means for introducing a dopant into said plasma in said plasma containment chamber in order to selectively reduce spectral interference from said plasma containment chamber, said dopant comprising a gas of a material for selective combination with molecular species which would otherwise produce interfering emissions in said plasma in the red and infrared regions of the electromagnetic spectrum.
Claim 3
Dependent Claim
15 words
The detector of claim wherein the same plasma containment chamber is a fused silica tube.
Claim 4
Dependent Claim
18 words
The detector of claim 2 wherein said tube has an i.d. of between 0.05 mm and 10 mm.
Claim 5
Dependent Claim
15 words
The detector of claim 2 wherein said tube is a portion of a chromatographic column.
Claim 6
Dependent Claim
15 words
The detector of claim 1 wherein the said plasma containment chamber is a sapphire tube.
Claim 7
Dependent Claim
19 words
The detector of claim 5 wherein the said tube has an i.d. of between 0.05 mm and 10 mm.
Claim 8
Dependent Claim
16 words
The detector of claim 1 wherein the said plasma containment chamber is a boron nitride tube.
Claim 9
Dependent Claim
19 words
The detector of claim 7 wherein said tube has an internal diameter of between 0.05 mm and 10 mm.
Claim 10
Dependent Claim
23 words
The detector of claim 1 wherein the said plasma containment chamber has a transparent portion which allows viewing of the said spectral emissions.
Claim 11
Dependent Claim
31 words
The detector of claim 1 wherein the said viewing means is an opening passing through any materials obscuring direct viewing of the said transparent portion of the said plasma containment chamber.
Claim 12
Dependent Claim
21 words
The detector of claim 1 wherein the said sampling means is a connection to the outlet end of a chromatographic column.
Claim 13
Dependent Claim
11 words
The detector of claim 1 wherein the sampling means is heated.
Claim 14
Dependent Claim
40 words
The detector of claim 12 wherein the sampling means is heated as a consequence of its being within, or a portion of, the detector base or the heating block, which base and heating block are heated in a controlled manner.
Claim 15
Dependent Claim
27 words
The detector of claim 1 wherein the sampling means is positioned such that the sample is introduced directly into the plasma of the electrical discharge region. 16.
Claim 16
Dependent Claim
18 words
The detector of claim 1 wherein the said plasma means is an alternating current radio frequency electrical discharge.
Claim 17
Dependent Claim
22 words
The alternating current radio frequency electrical discharge of claim 15 wherein said discharge passes between a high potential electrode and a ground.
Claim 18
Dependent Claim
11 words
The detector of claim 1 wherein the said plasma is helium.
Claim 19
Dependent Claim
37 words
The detector of claim 1 wherein the said plasma means directs the electrical discharge through the plasma containment chamber, by having the discharge extend from a small surface area of the high potential electrode to the ground.
Claim 20
Dependent Claim
30 words
The detector of claim 1 wherein said plasma means is electrically insulated by an insulator which encases the plasma containment chamber and separates the high potential electrode and the ground.
Claim 21
Dependent Claim
17 words
The detector of claim 19 wherein the said insulator is any material having a high dielectric constant.
Claim 22
Dependent Claim
12 words
The detector of claim 19 wherein the said insulator is a ceramic.
Claim 23
Dependent Claim
13 words
The detector of claim 19 wherein the said insulator is a metallic oxide.
Claim 24
Dependent Claim
22 words
The detector of claim 1 wherein the said plasma means has an inlet to receive plasma gas into the plasma containment chamber.
Claim 25
Dependent Claim
21 words
The detector of claim 1 wherein the said monitoring means is a monochromator optimized for use in the near-infrared spectral region.
Claim 26
Dependent Claim
15 words
The detector of claim 1 wherein the said monitoring means is a Fourier transform spectrometer.
Claim 27
Dependent Claim
21 words
The detector of claim 1 wherein the said monitoring means is a spectrograph with a photodiode array in the focal plane.
Claim 28
Dependent Claim
25 words
The detector of claim 1 wherein said dopant is controllably introduced in the plasma gas prior to exposure to the said creation of spectral emissions.
Claim 29
Dependent Claim
13 words
The detector of claim 1 wherein the said dopant is O 2 .
Claim 30
Dependent Claim
14 words
The detector of claim 1 wherein the said dopant is a halogen containing compound.
Claim 31
Dependent Claim
12 words
The detector of claim 29 wherein said compound is SF 6 .
Claim 32
Dependent Claim
25 words
The detector of claim 1, wherein said monitoring means further comprises a filter adapted to pass red and infrared radiation and absorb shorter wavelength radiation.
Claim 33
Dependent Claim
151 words
An alternating current radio frequency plasma discharge apparatus for element specific detection in multi-element chromatographic eluents comprising: sample introduction means; plasma gas inlet means; a plasma containment chamber; discharge electrodes having means for directing an electrical discharge through the plasma containment chamber; means for the electrical isolation of the plasma containment chamber; viewing window means for exposing a portion of the discharge region in the plasma containment chamber; means for isolating the plasma containment chamber from atmospheric contamination; means for allowing the plasma containment chamber to be purged of atomized elements and other effluents; means for monitoring selected molecular emissions from said plasma in the red and infrared regions of the electromagnetic spectrum; means for introducing a constant supply of molecular species into the plasma for reaction with other molecular species which would otherwise produce undesirable emissions in the red and infrared in the plasma; and plasma containment chamber decarbonization means.
Claim 34
Dependent Claim
151 words
An alternating current radio frequency plasma discharge apparatus for element specific detection in multi-element chromatographic eluents comprising: sample introduction means; plasma gas inlet means; a plasma containment chamber; discharge electrodes having means for directing an electrical discharge through the plasma containment chamber; means for the electrical isolation of the plasma containment chamber; viewing window means for exposing a portion of the discharge region in the plasma containment chamber; means for isolating the plasma containment chamber from atmospheric contamination; means for allowing the plasma containment chamber to be purged of atomized elements and other effluents; means for monitoring selected molecular emissions from said plasma in the red and infrared regions of the electromagnetic spectrum; means for introducing a constant supply of molecular species into the plasma for reaction with other molecular species which would otherwise produce undesirable emissions in the red and infrared in the plasma; and plasma containment chamber decarbonization means.
Claim 35
Dependent Claim
21 words
The apparatus of claim 32 wherein the sample introduction means is a connection to the outlet end of a chromatographic column.
Claim 36
Dependent Claim
12 words
The apparatus of claim 32 wherein the sample introduction means is heated.
Claim 37
Dependent Claim
38 words
The apparatus of claim 34 further comprising detector base means and means for heating said detector base means in a controlled manner, and wherein the sample introduction means is in thermally conducting relation with said detector base means.
Claim 38
Dependent Claim
27 words
The apparatus of claim 32 wherein the sample introduction means is positioned such that the sample is introduced directly into the plasma of the electrical discharge region.
Claim 39
Dependent Claim
15 words
The apparatus of claim 32 wherein the plasma containment chamber is a fused silica tube.
Claim 40
Dependent Claim
18 words
The apparatus of claim 37 wherein said tube has an i.d. of between 0.05 mm and 10 mm.
Claim 41
Dependent Claim
15 words
The apparatus of claim 37 wherein said tube is a portion of a chromatographic column.
Claim 42
Dependent Claim
14 words
The apparatus of claim 32 wherein the plasma containment chamber is a sapphire tube.
Claim 43
Dependent Claim
19 words
The apparatus of claim 40 wherein the said tube has an i.d. of between 0.05 mm and 10 mm.
Claim 44
Dependent Claim
15 words
The apparatus of claim 32 wherein the plasma containment chamber is a boron nitride tube.
Claim 45
Dependent Claim
19 words
The apparatus of claim 42 wherein said tube has an internal diameter of between 0.05 mm and 10 mm.
Claim 46
Dependent Claim
38 words
The apparatus of claim 32 wherein the means of directing the electrical discharge through the plasma containment chamber is achieved by having the discharge extend from a small surface area of the high potential electrode to the ground.
Claim 47
Dependent Claim
18 words
The apparatus of claim 44 wherein said ground is the base of the detector which is electrically grounded.
Claim 48
Dependent Claim
36 words
The apparatus of claim 32 wherein the means for the electrical isolation of the plasma containment chamber is an insulator which electrically isolates the plasma containment chamber, and separates the high potential electrode and the ground.
Claim 49
Dependent Claim
17 words
The detector of claim 46 wherein the said insulator is any material having a high dielectric constant.
Claim 50
Dependent Claim
12 words
The detector of claim 46 wherein the said insulator is a ceramic.
Claim 51
Dependent Claim
13 words
The detector of claim 46 wherein the said insulator is a metallic oxide.
Claim 52
Dependent Claim
23 words
The apparatus of claim 32 wherein said plasma gas inlet means is a tube which delivers plasma gas to the plasma containment chamber.
Claim 53
Dependent Claim
28 words
The apparatus of claim 32 wherein the viewing window is an opening passing through the insulator which exposes portion of the discharge region of the plasma containment chamber.
Claim 54
Dependent Claim
20 words
The apparatus of claim 32 wherein said monitoring means is a monochromator optimized for use in the near-infrared spectral region.
Claim 55
Dependent Claim
17 words
The monochromator of claim 32 wherein the monochromator has a small f number and large entrance slits.
Claim 56
Dependent Claim
14 words
The apparatus of claim 32 wherein said monitoring means is a Fourier transform spectrometer.
Claim 57
Dependent Claim
19 words
The apparatus of claim 32 wherein said monitoring means is spectrograph with a photodiode array in the focal plane.
Claim 58
Dependent Claim
23 words
The apparatus of claim 32 wherein the molecular species which is introduced to prevent undesirable emission in the plasma is O 2 .
Claim 59
Dependent Claim
23 words
The apparatus of claim 32 wherein the molecular species which is introduced to prevent undesirable emission in the plasma is a halogen-containing compound.
Claim 60
Dependent Claim
23 words
The apparatus of claim 32 wherein the molecular species which is introduced to prevent undesirable emission in the plasma is SF 6 .
Claim 61
Dependent Claim
23 words
The apparatus of claim 32 wherein the molecular species which is introduced to prevent undesirable emission in the plasma is a halogenated hydrocarbon.
Claim 62
Dependent Claim
23 words
The apparatus of claim 32 wherein the decarbonization means is means for controllably adding O 2 as a dopant to the plasma gas.
Claim 63
Dependent Claim
31 words
The apparatus of claim 32 wherein the decarbonization means is a heating means used to heat the plasma containment chamber is order to pyrolyze residues which form on the chamber walls.
Claim 64
Dependent Claim
35 words
The apparatus of claim 32 further comprising a filter disposed between said viewing window means and said means for monitoring, said filter being adapted to pass red and infrared radiation and absorb shorter wavelength radiation.
Claim 65
Independent Claim
172 words
A method for detecting specific elements in an effluent stream of a chromatograph comprising: obtaining a plasma containment chamber having an inlet, an outlet, and a viewing means for exposing a portion of said plasma containment chamber to monitoring means; introducing a sample from the effluent stream of a chromatograph into said plasma containment chamber; creating a plasma in said plasma containment chamber such that the plasma excites atomic and molecular components in said samples, thereby creating spectral emissions; monitoring said spectral emissions through a viewing means using a monitoring means comprised of a monochromator sensitive to red and infrared radiation, and having a small f number and large entrance slits; and introducing a dopant into said plasma in said plasma containment chamber for the selective reduction of spectral interferences from said plasma containment chamber, said dopant being comprised of a gaseous medium for the selective prevention of the formation of molecular species which would otherwise produced undesirable emission in said plasma in the red and infrared region of the electromagnetic spectrum.
Claim 66
Independent Claim
172 words
A method for detecting specific elements in an effluent stream of a chromatograph comprising: obtaining a plasma containment chamber having an inlet, an outlet, and a viewing means for exposing a portion of said plasma containment chamber to monitoring means; introducing a sample from the effluent stream of a chromatograph into said plasma containment chamber; creating a plasma in said plasma containment chamber such that the plasma excites atomic and molecular components in said samples, thereby creating spectral emissions; monitoring said spectral emissions through a viewing means using a monitoring means comprised of a monochromator sensitive to red and infrared radiation, and having a small f number and large entrance slits; and introducing a dopant into said plasma in said plasma containment chamber for the selective reduction of spectral interferences from said plasma containment chamber, said dopant being comprised of a gaseous medium for the selective prevention of the formation of molecular species which would otherwise produced undesirable emission in said plasma in the red and infrared region of the electromagnetic spectrum.
Claim 67
Dependent Claim
25 words
The method as set forth in claim 63 wherein the step of obtaining said plasma containment chamber is accomplished by using a fused silica tube.
Claim 68
Dependent Claim
20 words
The method as forth in claim 64 wherein said tube has an i.d. of between 0.05 mm and 10 mm.
Claim 69
Dependent Claim
27 words
The method as set forth in claim 63 wherein the step of obtaining said plasma containment chamber is accomplished by using a portion of a chromatographic column.
Claim 70
Dependent Claim
24 words
The method as set forth in claim 63 wherein the step of obtaining said plasma containment chamber is accomplished by using a sapphire tube.
Claim 71
Dependent Claim
21 words
The method as set forth in claim 67 wherein said tube has an i.d. of between 0.05 mm and 10 mm.
Claim 72
Dependent Claim
25 words
The method as set forth in claim 63 wherein the step of obtaining said plasma containment chamber is accomplished by using a boron nitride tube.
Claim 73
Dependent Claim
22 words
The method as set forth in claim 69 wherein said tube has an internal diameter of between 0.05 mm and 10 mm.
Claim 74
Dependent Claim
35 words
The method as set forth in claim 63 wherein the step of obtaining said plasma containment chamber is accomplished by using a chamber which has a transparent portion allowing viewing of the said spectral emissions.
Claim 75
Dependent Claim
38 words
The method as set forth in claim 63 wherein the step of obtaining a viewing means includes creating an opening passing through any materials obstructing direct viewing of the said transparent portion of the said plasma containment chamber.
Claim 76
Dependent Claim
25 words
The method as set forth in claim 63 wherein introducing a sample is accomplished through a connection to the outlet end of a chromatograph column.
Claim 77
Dependent Claim
24 words
The method as set forth in claim 63 wherein the introduction of said sample into said plasma containment chamber utilizes a heated introduction means.
Claim 78
Dependent Claim
42 words
The method as set forth in claim 74 wherein the said heated sampling means is obtained as a consequence of passing the sample within the detector base or the heating block, which base and heating block are heated in a controlled manner.
Claim 79
Dependent Claim
37 words
The method as set forth in claim 63 wherein the introduction of a sample is accomplished by positioning the introduction means such that the said sample is introduced directly into the plasma of the electrical discharge region.
Claim 80
Dependent Claim
24 words
The method as set forth in claim 62 wherein the creation of the plasma is accomplished using an alternating current radio frequency electrical discharge.
Claim 81
Dependent Claim
30 words
The method as set forth in claim 77 wherein the said alternating current radio-frequency electrical discharge is achieved by passing a discharge between a high potential electrode and a ground.
Claim 82
Dependent Claim
20 words
The method as set forth in claim 63 wherein the said plasma is formed from a plasma which is helium.
Claim 83
Dependent Claim
41 words
The method as set forth in claim 63 wherein the said plasma is created using an electrical discharge which passes through the plasma containment chamber, said discharge extending from a small surface area of the high potential electrode to the ground.
Claim 84
Dependent Claim
35 words
The method as set forth in claim 63 wherein the said plasma containment chamber is electrically insulated using an insulator which encases the plasma containment chamber and separates the high potential electrode and the ground.
Claim 85
Dependent Claim
19 words
The method as set forth in claim 81 wherein the insulator is any material having a high dielectric constant.
Claim 86
Dependent Claim
15 words
The method as set forth in claim 81 wherein the said insulator is a ceramic.
Claim 87
Dependent Claim
16 words
The method as set forth in claim 81 wherein the said insulator is a metallic oxide.
Claim 88
Dependent Claim
27 words
The method as set forth in claim 63 wherein the said plasma containment chamber has an inlet to receive plasma gas into the said plasma containment chamber.
Claim 89
Dependent Claim
25 words
The method as set forth in claim 63 wherein the said monitoring is achieved using a monochromator optimized for use in the near-infrared spectra region.
Claim 90
Dependent Claim
19 words
The method as set forth in claim 63 wherein the said monitoring is achieved using a Fourier transform spectrometer.
Claim 91
Dependent Claim
25 words
The method as set forth in claim 63 wherein the said monitoring is accomplished using a spectrograph with a photodiode array in the focal plane.
Claim 92
Dependent Claim
26 words
The method as set forth in claim 63 wherein said introduction of a dopant is made into the plasma gas prior to excitation in the discharge.
Claim 93
Dependent Claim
16 words
The method as set forth in claim 63 wherein the dopant introduced is O 2 .
Claim 94
Dependent Claim
17 words
The method as set forth in claim 63 wherein the dopant introduced is a halogen containing compound.
Claim 95
Dependent Claim
17 words
The method as set forth in claim 91 wherein the halogen containing compound is SF 6 .
Claim 96
Dependent Claim
33 words
The method of claim 62 comprising the further step of disposing a filter means between said viewing means and said monitoring means for passing red and infrared radiation and absorbing shorter wavelength radiation.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-24 | 1993-01-23 | 1993-07-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-24 | 1997-01-23 | 1997-07-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-24 | 2001-01-23 | 2001-07-25 | $7700.00 | Window Closed / Lapsed |