US5338931A
Expired / Lapsed
US
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Photoionization ion mobility spectrometer
Assignee: Environmental Technologies Group Inc
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Filing: 1992-04-23
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Granted: 1994-08-16
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Expires: 2012-04-23
Abstract
Abstract An improved photoionization ion mobility spectrometer is disclosed which utilizes a flashlamp as the source for ionization. A gas sample is introduced via a carrier gas into a ionization chamber which is part of the spectrometer cell. Ionizable molecules contained in the injected gas sample are ionized by the ultraviolet light emitted from the flashlamp. The ionized molecules are attracted by an electrostatic drift field into a drift chamber and travel therethrough against the flow of a drift gas counter-current thereto until they are captured by a collector located in the drift chamber opposite to the ionization chamber. A dopant with an effective ionization potential lower than the photon energy of the emitted light can be introduced into the ionization chamber to further improve the sensitivity and specificity.
Inventors
- 👤 Glenn E. Spangler
- 👤 Joseph E. Roehl
- 👤 Gautam B. Patel
- 👤 Alvin Dorman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 02:28
CPC Classifications
H; H01; H01J; H01J49/00; H01J49/02; H01J49/10; H01J49/16; H01J49/161; H01J49/162; G; G01; G01N; G01N27/00; G01N27/62; G01N27/622
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
281 words
An improved photoionization ion mobility spectrometer system for the detection of ionizable chemical species, comprising: (a) a housing having a main chamber therein, said main chamber comprising a photoionization chamber and a drift chamber; (b) drift gas inlet passage in communication with said drift chamber for entering a drift gas therethrough; (c) an exhaust passage in communication with said photoionization chamber for exiting said drift gas; (d) pumping means for forcing said drift gas to travel in said main chamber in a first direction; (e) a carrier gas inlet passage in communication with said photoionization chamber for introducing a carrier gas into said photoionization chamber; (f) a gas sample inlet means in communication with said photoionizaton chamber for introducing a gas sample to be analyzed into said photoionization chamber; (g) a lamp means exposed to said photoionization chamber for ionizing said gas sample therein to form ionized gas sample, said lamp means comprising (i) an electrical pulse transformer, (ii) a flashlamp filled with about two atmospheres of noble gas and sealed with a window for transmitting light with desired wavelength, and (iii) said flashlamp further containing two electrodes and at least one trigger probe, said trigger probe being connected to said pulse transformer and said electrodes being connected to a capacitor of high energy, said capacitor being adapted to discharge when a trigger pulse from said pulse transformer causes an ionization of said noble gas in said flashlamp and a discharge of said capacitor; (h) electrode means for driving said ionized gas sample in said main chamber in a second direction countercurrent to said first direction; and (i) detector means placed in said drift chamber for detecting said ionized gas sample.
Claim 2
Dependent Claim
281 words
An improved photoionization ion mobility spectrometer system for the detection of ionizable chemical species, comprising: (a) a housing having a main chamber therein, said main chamber comprising a photoionization chamber and a drift chamber; (b) drift gas inlet passage in communication with said drift chamber for entering a drift gas therethrough; (c) an exhaust passage in communication with said photoionization chamber for exiting said drift gas; (d) pumping means for forcing said drift gas to travel in said main chamber in a first direction; (e) a carrier gas inlet passage in communication with said photoionization chamber for introducing a carrier gas into said photoionization chamber; (f) a gas sample inlet means in communication with said photoionizaton chamber for introducing a gas sample to be analyzed into said photoionization chamber; (g) a lamp means exposed to said photoionization chamber for ionizing said gas sample therein to form ionized gas sample, said lamp means comprising (i) an electrical pulse transformer, (ii) a flashlamp filled with about two atmospheres of noble gas and sealed with a window for transmitting light with desired wavelength, and (iii) said flashlamp further containing two electrodes and at least one trigger probe, said trigger probe being connected to said pulse transformer and said electrodes being connected to a capacitor of high energy, said capacitor being adapted to discharge when a trigger pulse from said pulse transformer causes an ionization of said noble gas in said flashlamp and a discharge of said capacitor; (h) electrode means for driving said ionized gas sample in said main chamber in a second direction countercurrent to said first direction; and (i) detector means placed in said drift chamber for detecting said ionized gas sample.
Claim 3
Dependent Claim
15 words
The improved photoionization ion mobility spectrometer of claim 1 wherein said noble gas is krypton.
Claim 4
Dependent Claim
17 words
The improved photoionization ion mobility spectrometer of claim 1 wherein said window is a magnesium fluoride window.
Claim 5
Dependent Claim
32 words
The improved photoionization ion mobility spectrometer of claim 1 wherein said at least one trigger probe being disposed between said two electrodes to form a guided arc when said capacitor is discharged.
Claim 6
Dependent Claim
33 words
The improved photoionization ion mobility spectrometer of claim 1 wherein said flashlamp containing two or more trigger probes disposed between said two electrodes to form a guided arc when said capacitor is discharged.
Claim 7
Dependent Claim
20 words
The improved photoionization ion mobility spectrometer of claim 1 wherein said flashlamp is a bulb-type flashlamp having an unconfined arc.
Claim 8
Dependent Claim
32 words
The improved photoionization ion mobility spectrometer of claim 1 wherein said flashlamp having a short pulse duration in the microseconds range, typically between 0.7 and 1.5 microseconds, when said capacitor is discharged.
Claim 9
Dependent Claim
51 words
The improved photoionization ion mobility spectrometer of claim 1 further comprising an ion shutter grid separating said photoinization and drift chambers, said ion shutter grid being electrically pulsed to allow an intermittent passage of said ionized gas sample therethrough and wherein said flashlamp and said ion shutter grid are pulsed simultaneously.
Claim 10
Dependent Claim
53 words
The improved photoionization ion mobility spectrometer of claim 1 further comprising an ion shutter grid separating said photoionization and drift chambers, said ion shutter grid being electrically pulsed to allow an intermittent passage of said ionized gas sample therethrough and wherein said ion shutter grid has a delayed pulse relative to said flashlamp.
Claim 11
Dependent Claim
52 words
The improved photoionization ion mobility spectrometer of claim 1 further comprising an ion shutter grid separating said photoionization and drift chambers, said ion shutter grid being electrically pulsed to allow an intermittent passage of said ionized gas sample therethrough and wherein said shutter grid and said flashlamp have the same pulse width.
Claim 12
Dependent Claim
51 words
The improved photoionization ion mobility spectrometer of claim 1 further comprising an ion shutter grid separating said photoionization and drift chambers, said ion shutter grid being electrically pulsed to allow an intermittent passage of said ionized gas sample therethrough and wherein said shutter grid and said flashlamp have different pulse width.
Claim 13
Dependent Claim
21 words
The improved photoionization ion mobility spectrometer of claim 1 wherein both said drift gas and said carrier gas are purified air.
Claim 14
Dependent Claim
16 words
The improved photoionization ion mobility spectrometer of claim 1 wherein said pumping means comprises pneumatic means.
Claim 15
Dependent Claim
30 words
The improved photoionization ion mobility spectrometer of claim 1 further comprises separate controlled means for controlling flow rates of said carrier gas and said drift gas into said main chamber.
Claim 16
Dependent Claim
21 words
The improved photoionization ion mobility spectrometer of claim 1 further comprising a means for introducing a dopant into said photoionization chamber.
Claim 17
Dependent Claim
54 words
The improved photoionization ion mobility spectrometer of claim 15 wherein said means for introducing a dopant into said photoionization chamber comprises a blending means by which said dopant is introduced into said carrier gas using a permeation tube, diffusion tube or other suitable means before said carrier gas enters said carrier gas inlet passage.
Claim 18
Dependent Claim
39 words
The improved photoionization ion mobility spectrometer of claim 15 wherein said dopant comprises chemical species having an ionization potential less than the photon energy corresponding to the wavelength of the light of maximum intensity emitted by said flashlamp means.
Claim 19
Dependent Claim
78 words
The improved photoionization ion mobility spectrometer of claim 1 further comprising a means for introducing a dopant into said photoionization chamber, wherein said dopant comprises chemical species having an ionization potential less than the maximum photon energy corresponding to the shortest wavelength of the light emitted by said flashlamp means and wherein said flashlamp means comprises a flashlamp filled with krypton and sealed with a magnesium fluoride window, and said photon energy is about 10.0 to 10.2 eV.
Claim 20
Dependent Claim
14 words
The improved photoionization ion mobility spectrometer of claim 18 wherein said dopant is acetone.
Claim 21
Dependent Claim
21 words
The improved photoionization ion mobility spectrometer of claim 1 wherein said ionized gas sample is either positively charged or negatively charged.
Claim 22
Dependent Claim
55 words
The improved photoionization ion mobility spectrometer of claim 1 further comprising a means for introducing a dopant into said photoionization chamber and wherein said dopant comprises chemical species which has an ionization potential greater than the maximum photon energy corresponding to the shortest emitted by said flashlamp means but can be photoionized through indirect means.
Claim 23
Independent Claim
92 words
A method for improving the sensitivity of photoionization ion mobility spectrometer, said photoionization ion mobility spectrometer having photoionization means, a photoionization chamber, a drift chamber, drift gas inlet passage for introducing a drift gas into the drift chamber, carrier gas inlet passage for introducing a carrier gas containing gas sample to be analyzed into the photoionization chamber, wherein said improvement comprises: (a) using a flashlamp means as the photoionization mean; (b) said flashlamp comprising a pulse transformer and a flashlamp; and (c) said flashlamp having a pulse duration in the microsecond range.
Claim 24
Independent Claim
92 words
A method for improving the sensitivity of photoionization ion mobility spectrometer, said photoionization ion mobility spectrometer having photoionization means, a photoionization chamber, a drift chamber, drift gas inlet passage for introducing a drift gas into the drift chamber, carrier gas inlet passage for introducing a carrier gas containing gas sample to be analyzed into the photoionization chamber, wherein said improvement comprises: (a) using a flashlamp means as the photoionization mean; (b) said flashlamp comprising a pulse transformer and a flashlamp; and (c) said flashlamp having a pulse duration in the microsecond range.
Claim 25
Dependent Claim
55 words
The method for improving the sensitivity of photoionization ion mobility spectrometer of claim 22 further comprises the step of introducing a dopant into the carrier gas, said dopant comprising chemical species having an ionization potential less than the photon energy corresponding to the wavelength of the light of maximum intensity emitted by said flashlamp means.
Claim 26
Dependent Claim
43 words
The method of claim 23 wherein said dopant comprises chemical species which has an ionization potential greater than the photon energy corresponding to the wavelength of the light of maximum intensity emitted by said flashlamp means but can be photoionized through indirect means.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-08-15 | 1998-02-14 | 1998-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-08-15 | 2002-02-14 | 2002-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-08-15 | 2006-02-14 | 2006-08-16 | $7700.00 | Window Closed / Lapsed |