US3786249A
Expired / Lapsed
US
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Negative ion duoplasmatron mass spectrometer for isotope ratio analysis
Assignee: SRI International Inc
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Filing: 1971-12-20
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Granted: 1974-01-15
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Expires: 1991-12-20
Abstract
Abstract A technique for performing isotope ratio analysis is described which utilizes a negative ion mass spectrometer coupled with a negative ion duoplasmatron source. An untreated sample to be analyzed for a specific compound is diluted with a known amount of isotopic analog. The sample plus analog is volatilized if necessary, and purified by gas chromatography before entering the ion source. The extremely hot plasma of the duoplasmatron thoroughly fragments the large molecules and efficiently ionizes the input gas stream. The resulting ionized stream is analyzed in a magnetic mass spectrometer. The signals from a pair of peaks representing the common and noncommon tag isotope of the same element are converted to frequency signals and the frequency signals are converted to a ratio signal by a frequency ratio counter. The value of this ratio then indicates the precise amount of compound in the sample. The system operates very efficiently on stable, non-radioactive isotopes and is applicable to many analyses which cannot be performed with radioactive isotopes.
Inventors
- 👤 M Anbar
- 👤 W Aberth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 06:02
CPC Classifications
H; H01; H01J; H01J49/00; H01J49/02; H01J49/10; H01J49/12; H01J49/123; H01J49/26; H01J49/28; H01J49/30
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
123 words
A method of determining the quantity of a substance in a sample comprising the steps of: adding a measured amount of an isotopic analog of the substance to the sample to form a mixture; ionizing and fragmenting the mixture in a hot plasma to form ionized fragments of the substance and isotopic analog; extracting the negative ion fragments as a beam from the hot plasma; magnetically separating the beam into a first and second beam corresponding to negatively ionized fragments of the substance and negatively ionized fragments of the isotopic analog; measuring the intensity of said first and second beams; and ratioing the measured intensities of said first and second beams, whereby the quantity of said substance in said sample may be determined.
Claim 2
Independent Claim
123 words
A method of determining the quantity of a substance in a sample comprising the steps of: adding a measured amount of an isotopic analog of the substance to the sample to form a mixture; ionizing and fragmenting the mixture in a hot plasma to form ionized fragments of the substance and isotopic analog; extracting the negative ion fragments as a beam from the hot plasma; magnetically separating the beam into a first and second beam corresponding to negatively ionized fragments of the substance and negatively ionized fragments of the isotopic analog; measuring the intensity of said first and second beams; and ratioing the measured intensities of said first and second beams, whereby the quantity of said substance in said sample may be determined.
Claim 3
Dependent Claim
14 words
A method according to claim 1 further including the step of vaporizing said mixture.
Claim 4
Dependent Claim
14 words
A method according to claim 1 further including the step of purifying said sample.
Claim 5
Dependent Claim
19 words
A method according to claim 3 in which the mixture is purified by passage through a gas chromatographic column.
Claim 6
Dependent Claim
18 words
A method according to claim 1 further including the step of dispersing said mixture in a carrier gas.
Claim 7
Dependent Claim
16 words
A method according to claim 5 in which the carrier gas is unreactive with the sample.
Claim 8
Dependent Claim
22 words
A method according to claim 5 in which the carrier gas reacts with the sample to form ionized fragments containing said isotope.
Claim 9
Dependent Claim
22 words
A method according to claim 7 in which the carrier gas is selected from a group consisting of nitrogen, oxygen and hydrogen.
Claim 10
Dependent Claim
12 words
A method according to claim 1 in which the isotope is non-radioactive.
Claim 11
Dependent Claim
24 words
A method according to claim 1 in which the sample contains a first isotopic concentration and the analog contains a substantially different isotopic concentration.
Claim 12
Dependent Claim
24 words
A method according to claim 1 in which the isotopes are selected from a group consisting of D, 13C, 15N, 18 O, and 36S.
Claim 13
Dependent Claim
31 words
A method according to claim 11 in which the substance contains a first concentration of at least one of said isotopes and the analog contains a lower concentration of said isotopes.
Claim 14
Dependent Claim
18 words
A method according to claim 11 in which the added analog contains a higher concentration of said isotopes.
Claim 15
Dependent Claim
37 words
A method according to claim 1 in which the substance and analog are organic compounds containing at least one of the atoms selected from the group consisting of C, H, O, N and S and isotopes thereof.
Claim 16
Dependent Claim
37 words
A method according to claim 14 in which the sample is a biological fluid and said isotopes are substituted on non-labile positions of said compound that are not dissociated by the biological system of the animal subject.
Claim 17
Dependent Claim
22 words
A method according to claim 1 in which the dilution ratio of said substance to said analog is from 1:25 to 1:107.
Claim 18
Dependent Claim
22 words
A method according to claim 16 in which the sample contains from 10 1 grams to 10 10 grams of said substance.
Claim 19
Dependent Claim
70 words
A method according to claim 15 in which said sample is a pharmaceutical and further including determining the persistence level of the pharmaceutical by administering a material selected from the group consisting of said pharmaceutical and an isotopic analog thereof to a subject, recovering a sample of body fluid of the subject containing said material, adding a known amount of said isotopic analog to saId sample to form said mixture.
Claim 20
Dependent Claim
19 words
A method according to claim 1 in which said mixture is ionized and fragmented in a negative ion duoplasmatron.
Claim 21
Independent Claim
142 words
A method of determining the identity of an unknown first substance comprising the steps of: adding known amounts of isotopic forms of known different second substances to different aliquots of said first substance to form different mixtures, one of said different second substances being suspected as being the same as said unknown first substance; successively, for each different mixture, ionizing and fragmenting the mixture in a hot plasma to form a beam of negatively ionized fragments; magnetically separating the beam into a first beam path corresponding to the negatively ionized fragment of the said isotope and a second beam corresponding to the negatively ionized fragments of the first substance; measuring the intensity of the first and second beams, and observing the presence of a characteristic ratio of said first and second beams as an indication of the identity of said first substance.
Claim 22
Independent Claim
142 words
A method of determining the identity of an unknown first substance comprising the steps of: adding known amounts of isotopic forms of known different second substances to different aliquots of said first substance to form different mixtures, one of said different second substances being suspected as being the same as said unknown first substance; successively, for each different mixture, ionizing and fragmenting the mixture in a hot plasma to form a beam of negatively ionized fragments; magnetically separating the beam into a first beam path corresponding to the negatively ionized fragment of the said isotope and a second beam corresponding to the negatively ionized fragments of the first substance; measuring the intensity of the first and second beams, and observing the presence of a characteristic ratio of said first and second beams as an indication of the identity of said first substance.
Claim 23
Independent Claim
133 words
A method of identifying a batch of an organic chemical comprising the steps of: labeling the batch by adding a known amount of non-common isotopes to the batch at non-labile, non-dissociative positions of the chemical; recording the labeling information; forming a mixture of a known amount of a sample of the labeled compound and a known amount of a common isotopic analog thereof; introducing the mixture into a hot plasma to form a beam of negatively ionized fragments; magnetically separating the beam into a first beam path of the negatively ionized fragments containing the non-common isotope and a second beam of the negatively ionized fragments containing the common isotope; measuring the intensities of the first and second beams; determining the isotopic content of the chemical; and comparing it to the recorded labeling information.
Claim 24
Independent Claim
133 words
A method of identifying a batch of an organic chemical comprising the steps of: labeling the batch by adding a known amount of non-common isotopes to the batch at non-labile, non-dissociative positions of the chemical; recording the labeling information; forming a mixture of a known amount of a sample of the labeled compound and a known amount of a common isotopic analog thereof; introducing the mixture into a hot plasma to form a beam of negatively ionized fragments; magnetically separating the beam into a first beam path of the negatively ionized fragments containing the non-common isotope and a second beam of the negatively ionized fragments containing the common isotope; measuring the intensities of the first and second beams; determining the isotopic content of the chemical; and comparing it to the recorded labeling information.
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) | 1977-01-14 | 1977-07-16 | 1978-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-14 | 1981-07-16 | 1982-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-14 | 1985-07-16 | 1986-01-15 | $7700.00 | Window Closed / Lapsed |