US3843257A
Expired / Lapsed
US
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Microwave-excited emission detector
Assignee: Monsanto Research Corp
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Filing: 1973-06-18
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Granted: 1974-10-22
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Expires: 1993-06-18
Abstract
Abstract A multifunctional, multimode, selective microwave-excited emission detector is described which is capable of detecting and analyzing metallic and non-metallic compositions of organic or inorganic nature at subnanogram levels on an integrated or real time basis. The detector concept utilizes microwave energy at frequencies of 2.45 GHz (gigahertz, i.e., billion cycles) or higher to excite spectral emission of atomic and/or polyatomic constituents of the composition being analyzed. The microwaveexciting process can be carried out under pressure, at atmospheric pressure or at reduced pressures, however, for increased sensitivity pressures of the order of about 1 Torr or less are preferred and extremely high sensitivities can be attained by carrying out the discharge and excitation in a magnetic field sufficient to sustain the discharge at pressures of the order of 10 5 to 10 6 Torr using photon counters for detection. Definitive spectral lines or bands are isolated either by a diffraction grating monochromator or band-pass filters. The emission intensity of the spectral line(s) or band(s), which is a function of concentration, is measured by photomultiplier detectors and ancillary electronic read-out. A temperatureprogrammed sample pyrolysis probe can be used on liquid or solid samples to circumvent spectral interference problems. A reference channel in the electro-optical portion of the instrument can be used for stabilization or to null-out background or undesired interfering spectral lines. A multichannel optical system can be used to observe a number of different spectral lines at the same time, thereby detecting different emission lines of the same element or lines of a number of different elements simultaneously.
Inventors
- 👤 G Wooten
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 12:57
CPC Classifications
G; G01; G01N; G01N22/00; G01N21/00; G01N21/62; G01N21/66; G01N21/68
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
66 words
A method for exciting a gaseous sample comprising mixing said sample with a discharge gas, subjecting said mixture to a pressure of about 1 Torr or less, and irradiating said mixture under vacuum with sufficient microwave energy at frequencies of at least about 1 GHz to cause discharge gas to discharge and excite atoms in said sample to emit light of frequencies characteristic of the atoms.
Claim 2
Independent Claim
66 words
A method for exciting a gaseous sample comprising mixing said sample with a discharge gas, subjecting said mixture to a pressure of about 1 Torr or less, and irradiating said mixture under vacuum with sufficient microwave energy at frequencies of at least about 1 GHz to cause discharge gas to discharge and excite atoms in said sample to emit light of frequencies characteristic of the atoms.
Claim 3
Dependent Claim
32 words
A method of claim 1 wherein said irradiation is carried out in a magnetic field sufficient to sustain the gas discharge at a pressure of about 10 5 to 10 6 Torr.
Claim 4
Dependent Claim
139 words
A microwave-excited emission detector comprising: a. a hollow discharge tube, b. means to introduce a discharge gas to said tube, c. means to introduce a sample to said tube, d. a microwave energy source capable of generating microwaves having frequencies of at least about 1 GHz, e. means to irradiate inside discharge tube with said microwave energy, f. means adapted to view light emission from said discharge tube and separate a narrow band of light frequencies, g. means to view said narrow band of light frequencies and transform the light energy to electrical energy indicative of the intensity of said light energy, h. means to measure the quantity of said electrical energy, and i. vacuum means are connected to said discharge tube and are capable of maintaining a pressure in said discharge tube of about 1 Torr or less.
Claim 5
Dependent Claim
139 words
A microwave-excited emission detector comprising: a. a hollow discharge tube, b. means to introduce a discharge gas to said tube, c. means to introduce a sample to said tube, d. a microwave energy source capable of generating microwaves having frequencies of at least about 1 GHz, e. means to irradiate inside discharge tube with said microwave energy, f. means adapted to view light emission from said discharge tube and separate a narrow band of light frequencies, g. means to view said narrow band of light frequencies and transform the light energy to electrical energy indicative of the intensity of said light energy, h. means to measure the quantity of said electrical energy, and i. vacuum means are connected to said discharge tube and are capable of maintaining a pressure in said discharge tube of about 1 Torr or less.
Claim 6
Dependent Claim
59 words
A detector of claim 3 wherein magnetic means are provided capable of furnishing a magnetic field sufficient to sustain a gas discharge and in which to carry out the discharge and excitation, said vacuum means being capable of maintaining a pressure of about 10 5 to 10 6 Torr, and photon counter means are used for light emission detection.
Claim 7
Dependent Claim
90 words
A detector of claim 3 wherein a reference means is provided to view light emission from said discharge tube and separate a band of light energy to serve as a comparative reference to said narrow band of light frequencies, means to transform light energy from said reference means to electrical energy indicative of the intensity of said light energy, and means to compare the electrical energy from said narrow band of light frequencies with the electrical energy from said references means to increase the stability and sensitivity of said detector.
Claim 8
Dependent Claim
70 words
A detector of claim 3 wherein multiple means are provided to view light emission from said discharge tube, each of said multiple means separates a different narrow band of light frequencies, means are provided for each said multiple means to transform light energy to electrical energy indicative of the intensity of said light, and means are provided for each said multiple means to measure the quantity of said electrical energy.
Claim 9
Dependent Claim
23 words
A detector of claim 3 wherein means are provided to convert liquid and solid samples to gaseous form for analysis in said detector.
Claim 10
Dependent Claim
83 words
A microwave-exciting emission system comprising: a. a hollow discharge tube, b. means to introduce a discharge gas to said tube, c. means to introduce a sample to said tube, d. a microwave energy source capable of generating microwaves having frequencies of at least about 1 GHz, e. means to irradiate inside said discharge tube using said microwave energy, and f. vacuum means connected to said discharge tube and capable of maintaining a vacuum in said discharge tube of about 1 Torr or less.
Claim 11
Dependent Claim
83 words
A microwave-exciting emission system comprising: a. a hollow discharge tube, b. means to introduce a discharge gas to said tube, c. means to introduce a sample to said tube, d. a microwave energy source capable of generating microwaves having frequencies of at least about 1 GHz, e. means to irradiate inside said discharge tube using said microwave energy, and f. vacuum means connected to said discharge tube and capable of maintaining a vacuum in said discharge tube of about 1 Torr or less.
Claim 12
Dependent Claim
67 words
A system of claim 8 wherein said temperature-programmed probe is associated with said hollow discharge tube to discharge a vaporized sample into said tube, said probe comprising an electrical filament on which a liquid or solid sample can be deposited, and means to furnish current to said filament to gradually heat the filament in a programmed cycle of temperature and time sufficient to fractionally vaporize a sample.
Claim 13
Dependent Claim
128 words
A sample analysis method comprising the following steps: a. mixing a sample in gaseous form with a discharge gas, b. irradiating said mixture under vacuum at a pressure of about 1 Torr or less with sufficient microwave energy at a frequency at least about 1 GHz to cause said discharge gas to discharge and to excite atoms in said sample to emit light of frequencies characteristic of the atoms, c. separating from the light emitted by said irradiated mixture a narrow band of light frequencies containing a frequency characteristic of an atom for which analysis is being made, d. transforming said band of light frequencies from light energy to electrical energy indicative of the intensity of said light energy, and e. measuring the quantity of said electrical energy.
Claim 14
Dependent Claim
128 words
A sample analysis method comprising the following steps: a. mixing a sample in gaseous form with a discharge gas, b. irradiating said mixture under vacuum at a pressure of about 1 Torr or less with sufficient microwave energy at a frequency at least about 1 GHz to cause said discharge gas to discharge and to excite atoms in said sample to emit light of frequencies characteristic of the atoms, c. separating from the light emitted by said irradiated mixture a narrow band of light frequencies containing a frequency characteristic of an atom for which analysis is being made, d. transforming said band of light frequencies from light energy to electrical energy indicative of the intensity of said light energy, and e. measuring the quantity of said electrical energy.
Claim 15
Dependent Claim
33 words
A method of claim 10 wherein the discharge and excitation are carried out in a magnetic field sufficient to sustain the discharge and the pressure is about 10 5 to 10 6 Torr.
Claim 16
Dependent Claim
58 words
A method of claim 10 wherein a reference band of light frequencies is separated, said reference band is transformed from light energy to electrical energy indicative of the intensity of said reference light energy, and said reference electrical energy is compared with the electrical energy from said narrow Band to increase the stability and sensitivity of said method.
Claim 17
Dependent Claim
75 words
A method of claim 10 wherein multiple narrow bands of light of different frequencies are separated from the light emitted by said irradiated mixture and each band contains a frequency characteristic of an atom for which analysis is being made, the light of each said band is separately transformed from light energy to electrical energy indicative of the intensity of the light energy, and the quantity of electrical energy is measured for each said band.
Claim 18
Dependent Claim
59 words
A method of claim 13 wherein a reference band of light frequencies is separated, said reference band is transformed from light energy to electrical energy indicative of the intensity of said reference light energy, and said reference electrical energy is compared with the electrical energy of each multiple narrow band to increase the stability and sensitivity of said method.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-21 | 1978-04-22 | 1978-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-21 | 1982-04-22 | 1982-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-21 | 1986-04-22 | 1986-10-22 | $7700.00 | Window Closed / Lapsed |