Patent US4721854A successfully refreshed from Google Patents.
US4721854A
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Quadrupole mass spectrometer
Assignee: National Research Council Canada
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Filing: 1986-06-23
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Granted: 1988-01-26
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Expires: 2006-06-23
Abstract
Abstract This disclosure presents an alternative, improved approach to the RF only quadrupole mass spectrometers. The ions whose masses place them near the stability limit for a given operating voltage and RF frequency, can be strongly influenced by the application of a very small dc voltage to the quadrupole rods. If this voltage is modulated at a low frequency (typically a few hundred hertz), the (a,q) values will pass alternately through the stability boundary and ions will be transmitted with the imposed frequency. The advantages of the new approach are two-fold (a) lock-in amplifier synchronous detection schemes can be used. These give improved signal/noise ratios. Background noise due to photons, soft X-rays or excited neutrals--often a problem in quadrupole mass filters--will not be modulated and will not be detected. (b) Higher resolution can be achieved.
Inventors
- 👤 Peter H. Dawson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 07:23
CPC Classifications
H; H01; H01J; H01J49/00; H01J49/26; H01J49/34; H01J49/42; H01J49/4205; H01J49/421; H01J49/4215
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
188 words
In a vacuum quadrupole mass spectrometer having: quadrupole rod electrodes mutually arrranged in parallel with each other, an RF control unit connected to the said quadrupole rod electrodes to generate an RF field for mass filtering of ions in the RF-only mode within the stability boundary of the (a,q) values, an ion source near one end of the quadrupole rod electrodes to introduce to the RF field a beam of ions to be analyzed; and detector near the other end of the quadrupole rod electrodes to detect ions transmitted through the RF field and to produce a detector signal; the invention being characterized in that a modulation voltage source for producing a modulation voltage of a low frequency whose period is long compared to the flight time of the ions in the RF field; superimposing means for superimposing the modulation voltage on the RF field so that the (a,q) values will pass alternately through the stability boundary and the ions will be transmitted with the said low frequency; and a lock-in amplifier connected to the detector for amplifying the detector signal in synchronism with the said low frequency.
Claim 2
Dependent Claim
188 words
In a vacuum quadrupole mass spectrometer having: quadrupole rod electrodes mutually arrranged in parallel with each other, an RF control unit connected to the said quadrupole rod electrodes to generate an RF field for mass filtering of ions in the RF-only mode within the stability boundary of the (a,q) values, an ion source near one end of the quadrupole rod electrodes to introduce to the RF field a beam of ions to be analyzed; and detector near the other end of the quadrupole rod electrodes to detect ions transmitted through the RF field and to produce a detector signal; the invention being characterized in that a modulation voltage source for producing a modulation voltage of a low frequency whose period is long compared to the flight time of the ions in the RF field; superimposing means for superimposing the modulation voltage on the RF field so that the (a,q) values will pass alternately through the stability boundary and the ions will be transmitted with the said low frequency; and a lock-in amplifier connected to the detector for amplifying the detector signal in synchronism with the said low frequency.
Claim 3
Dependent Claim
39 words
The quadrupole mass spectrometer according to claim 1 wherein: the said RF control unit generates an RF field for mass filtering of ions in the RF-only mode within the first region of the stability boundary of the (a,q) values.
Claim 4
Dependent Claim
39 words
The quadrupole mass spectrometer according to claim 1 wherein: the said RF control unit generates an RF field for mass filtering of ions in the RF-only mode within the second region of the stability boundary of the (a,q) values.
Claim 5
Dependent Claim
29 words
The quadrupole mass spectrometer according to claim 2 wherein: the frequency of the RF field is 3 MHz and the amplitude of the modulation voltage is about one volt.
Claim 6
Dependent Claim
29 words
The quadrupole mass spectrometer according to claim 3 wherein the frequency of the RF field is 1.5 MHz and the amplitude of the modulation voltage is about 6 volts.
Claim 7
Dependent Claim
172 words
In a vacuum quadrupole mass spectrometer having quadrupole rod electrodes mutually arranged in parallel with each other, an RF control unti connected to the said quadrupole rod electrodes to generate an RF field for mass filtering of ions in the RF-only mode within the stability boundary of the (a,q) values, an ion source near one end of the quadrople rod electrodes to introduce to the RF field a beam of ions to be analyzed, and a detector near the other end of the quadrupole rod electrodes to detect ions transmitted through the RF field and to produce a detector signal, the invention being characterised in a method in that superimposing on the RF field a modulation voltage of a low frequency whose period is long compared to the flight time of the ions in the RF field so that the (a,q) values will pass alternately through the stability boundary and the ions will be transmitted with the said low frequency, and amplifying the detector signal in synchronism with the said low frequency.
Claim 8
Dependent Claim
172 words
In a vacuum quadrupole mass spectrometer having quadrupole rod electrodes mutually arranged in parallel with each other, an RF control unti connected to the said quadrupole rod electrodes to generate an RF field for mass filtering of ions in the RF-only mode within the stability boundary of the (a,q) values, an ion source near one end of the quadrople rod electrodes to introduce to the RF field a beam of ions to be analyzed, and a detector near the other end of the quadrupole rod electrodes to detect ions transmitted through the RF field and to produce a detector signal, the invention being characterised in a method in that superimposing on the RF field a modulation voltage of a low frequency whose period is long compared to the flight time of the ions in the RF field so that the (a,q) values will pass alternately through the stability boundary and the ions will be transmitted with the said low frequency, and amplifying the detector signal in synchronism with the said low frequency.
Claim 9
Dependent Claim
39 words
The method according to claim 6 wherein the RF control unit is set to generate an RF field for mass filtering of ions in the RF-only mode witin the first region of the stability boundary of the (a,q) values.
Claim 10
Dependent Claim
39 words
The method according to claim 6 wherein the RF control unit is set to generate an RF field for mass filtering of ions in the RF-only mode within the second region of the stability boundary of the (a,q) values.
Claim 11
Dependent Claim
27 words
The method according to claim 7 wherein the frequency of the RF field is 3 MHz and the amplitude of the modulation voltage is about one volt.
Claim 12
Dependent Claim
27 words
The method according to claim 8 wherein the frequency of the RF field is 1.5 MHz and the amplitude of the modulation voltage is about 6 volts.
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) | 1991-01-25 | 1991-07-27 | 1992-01-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-25 | 1995-07-27 | 1996-01-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-25 | 1999-07-27 | 2000-01-26 | $7700.00 | Window Closed / Lapsed |