Hand-held probe for real-time analysis of trace pollutants in atmosphere and on surfaces

• US 5,826,214 A
• Filed: 09/26/1996
• Issued: 10/20/1998
• Est. Priority Date: 09/26/1996
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Pastel, Robert L., Murray, Richard B., Lieb, Robert J., Sausa, Rosario C.
• Primary Examiner(s): KEMPER, MELANIE A
• Application Number:
  US08/744,704
• Time in Patent Office: 754 Days
• Field of Search: 364/498, 364/496, 364/497, 364/499, 364/550, 250/281, 250/288, 250/309, 250/373, 250/306, 250/389, 73/23.2, 73/31.01, 73/31.02, 73/31.03, 73/31.05, 73/35.14, 73/1.02, 436/106, 702/22, 702/24, 702/23
• US Class Current: 702/24
• CPC Class Codes: G01N 33/227 Explosives, e.g. combustive properties thereof detecting explosives in air G01N33/0057

Abstract

A hand-held probe monitors the presence of trace hazardous materials including nitrocompounds and halogen-containing compounds. The hand-held probe provides real-time and in-situ site characterization and analysis. The probe operates in accordance with a laser photofragmentation/fragment detection technique which employs one or more lasers for photolysis of the analyte molecules and/or facilitating the detection of the characteristic fragments by multiphoton ionization. The probe includes a tunable laser, a pair of miniature electrodes coupled with a fiberoptic cable and lens assembly mounted in a sweep wand, and a data and analysis system. An adjustable laser beam stopper allows for atmospheric sampling or surface analysis at the point of interest. Applications include the detection of nitrocompounds by probing the characteristic NO photofragment and halogenated compounds by probing the respective characteristic halogen atom photofragment. The monitoring of other hazardous materials and pollutants is possible.

Claims

1. A device for real-time and in situ detection of an halogenated explosive in a building, luggage or parcel, the device comprising:

a wand for obtaining a sample of the atmosphere;

the wand including an analysis region for holding the sample of the atmosphere and an aperture for allowing the sample of the atmosphere to enter the analysis region,

laser means for producing a laser beam and introducing the laser beam into the analysis region to fragment at least a portion of the sample of the atmosphere to produce a fragmentation product and to ionize the fragmentation produce to produce ions,

ionization detecting means for detecting the ions to produce a detection signal; and

data acquisition and analysis means, receiving the detection signal, for determining the presence of halogens in the vicinity.

2. A device as in claim 1, wherein the wand comprises a screen in the aperture.

3. A device as in claim 1, wherein the laser means comprises:

a laser operating substantially at 226 nm so as to produce the fragmentation result and to ionize an halogen fragment within the fragmentation result by resonance-enhanced ionization via an A² Σ

- X² Π

(0,0) band at 226 nm;

collimating means, receiving the laser beam from the laser, for collimating the laser beam;

fiber optic means, receiving the laser beam from the collimating means, for introducing the laser beam into the analysis region; and

focusing means, receiving the laser beam from the fiber optic means, for focusing the laser beam.

4. A device as in claim 1, wherein the ionization detecting means comprises:

a pair of electrodes in the analysis region for detecting the ions to produce a current; and

an amplifier, receiving the current, for amplifying the current to produce the detection signal.

5. A device as in claim 1, further comprising a removable beam block disposed in an optical path of the laser beam.

6. A device as in claim 1, wherein the laser means comprises:

a first laser for producing a first component of the laser beam for photofragmentation of the portion of the sample; and

a second laser for producing a second component of the laser beam for producing the ions by resonance-enhanced ionization of the fragmentation product.

7. A device as in claim 1, wherein the laser means comprises a plurality of lasers for producing the ions from the fragmentation product by a plurality of transitions of the fragmentation product or by multiphoton ionization.

8. A device as in claim 7, wherein the fragmentation product comprises NO, and the plurality of transitions comprise electronic, vibrational and rotational transitions.

9. A device as in claim 1, wherein the data acquisition and processing means comprises:

a gated boxcar integrator for integrating the detection signal to produce an integrated detection signal; and

a computer for analyzing the integrated detection signal to determine the presence of the impurities.

10. A device as in claim 9, wherein the computer comprises:

means for determining spectral signatures of the impurities from the integrated detection signal;

means for storing known spectral signatures indicating known concentrations of known impurities; and

means for comparing the spectral signatures determined by the means for determining with the known spectral signatures.

11. A device as in claim 9, wherein the data acquisition and processing means further comprises display means for providing a real-time display indicating the presence of the impurities.

12. A device as in claim 11, wherein the display means comprises a digital oscilloscope.

13. A device as in claim 11, wherein the display means comprises a chart recorder.

14. A device as in claim 11, wherein the display means comprises a monitor of the computer.

15. A device for real-time and in situ detection and monitoring of impurities on a surface, the device comprising:

a wand for being held adjacent to the surface;

laser means for producing a laser beam and introducing the laser beam onto the surface to volatilize a sample from the surface, to fragment at least a portion of the sample to produce a fragmentation product and to ionize the fragmentation product to produce ions;

ionization detecting means for detecting the ions to produce a detection signal; and

data acquisition and analysis means, receiving the detection signal, for determining a presence of the impurities in the atmosphere.

16. A device as in claim 15, wherein the laser means comprises:

a laser operating substantially at 226 nm so as to produce the fragmentation result and to ionize an NO fragment within the fragmentation result by resonance-enhanced ionization via an A² Σ

- X² Π

(0,0) band at 226 nm;

collimating means, receiving the laser beam from the laser, for collimating the laser beam;

fiber optic means, receiving the laser beam from the collimating means, for introducing the laser beam onto the surface; and

focusing means, receiving the laser beam from the fiber optic means, for focusing the laser beam.

17. A device as in claim 15, wherein the ionization detecting means comprises:

a pair of electrodes in the wand for detecting the ions to produce a current; and

an amplifier, receiving the current, for amplifying the current to produce the detection signal.

18. A device as in claim 15, further comprising a removable beam block disposed in an optical path of the laser beam.

19. A device as in claim 15, wherein the laser means comprises:

a first laser for producing a first component of the laser beam for photofragmentation of the portion of the sample; and

a second laser for producing a second component of the laser beam for producing the ions by resonance-enhanced ionization of the fragmentation product.

20. A device as in claim 15, wherein the laser means comprises a plurality of lasers for producing the ions from the fragmentation product by a plurality of transitions of the fragmentation product or by multiphoton ionization.

21. A device as in claim 15, wherein the impurities comprise halogenated compounds, and wherein the laser means comprises at least one laser for laser photofragmentation of the portion of the sample and ionization of the fragmentation result.

22. A device as in claim 15, wherein the data acquisition and processing means comprises:

a gated boxcar integrator for integrating the detection signal to produce an integrated detection signal; and

a computer for analyzing the integrated detection signal to determine the presence of the impurities.

23. A device as in claim 22, wherein the computer comprises:

means for determining spectral signatures of the impurities from the integrated detection signal;

means for storing known spectral signatures indicating known concentrations of known impurities; and

means for comparing the spectral signatures determined by the means for determining with the known spectral signatures.

24. A device as in claim 22, wherein the data acquisition and processing means further comprises display means for providing a real-time display indicating the presence of the impurities.

25. A device as in claim 24, wherein the display means comprises a digital oscilloscope.

26. A device as in claim 24, wherein the display means comprises a chart recorder.

27. A device as in claim 24, wherein the display means comprises a monitor of the computer.