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Characterization of nitrated sugar alcohols by atmospheric-pressure chemical-ionization mass spectrometry

February 28, 2017
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Journal Article
Author:
Alla Ostrinskaya
…
Published in:
Rapid Commun. Mass Spectrom., Vol. 33, 2017, pp. 333-43.
Topic:
detection systems
R&D area:
R&D group:

Summary

RATIONALE: The nitrated sugar alcohols mannitol hexanitrate (MHN), sorbitol hexanitrate (SHN) and xylitol pentanitrate (XPN) are in the same class of compounds as the powerful military-grade explosive pentaerythritol tetranitrate (PETN) and the homemade explosive erythritol tetranitrate (ETN) but, unlike for PETN and ETN, ways to detect MHN, SHN and XPN by mass spectrometry (MS) have not been fully investigated. METHODS: Atmospheric-pressure chemical-ionization mass spectrometry (APCI-MS) was used to detect ions characteristic of nitrated sugar alcohols. APCI time-of-flight mass spectrometry (APCI-TOF MS) and collision-induced dissociation tandem mass spectrometry (CID MS/MS) were used for confirmation of each ion assignment. In addition, the use of the chemical ionization reagent dichloromethane was investigated to improve sensitivity and selectivity for detection of MHN, SHN and XPN. RESULTS: All the nitrated sugar alcohols studied followed similar fragmentation pathways in the APCI source. MHN, SHN and XPN were detectable as fragment ions formed by the loss of NO2, HNO2, NO3, and CH2NO2 groups, and in the presence of dichloromethane chlorinated adduct ions were observed. It was determined that in MS/MS mode, chlorinated adducts of MHN and SHN had the lowest limits of detection (LODs), while for XPN the lowest LOD was for the [XPN-NO2]- fragment ion. Partially nitrated analogs of each of the three compounds were also present in the starting materials, and ions attributable to these compounds versus those formed from in-source fragmentation of MHN, SHN, and XPN were distinguished and assigned using liquid chromatography APCI-MS and ESI-MS. CONCLUSIONS: The APCI-MS technique provides a selective and sensitive method for the detection of nitrated sugar alcohols. The methods disclosed here will benefit the area of explosives trace detection for counterterrorism and forensics.
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Summary

RATIONALE: The nitrated sugar alcohols mannitol hexanitrate (MHN), sorbitol hexanitrate (SHN) and xylitol pentanitrate (XPN) are in the same class of compounds as the powerful military-grade explosive pentaerythritol tetranitrate (PETN) and the homemade explosive erythritol tetranitrate (ETN) but, unlike for PETN and ETN, ways to detect MHN, SHN and XPN...

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Characterization of nitrated sugar alcohols by atmospheric-pressure chemical-ionization mass spectrometry

Biomimetic sniffing improves the detection performance of a 3D printed nose of a dog and a commercial trace vapor detector

December 1, 2016
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Journal Article
Author:
Matthew E. Staymates
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Published in:
Scientific Reports, Vol. 6 , art. no. 36876, December 2016. DOI: 10.1038/srep36876.
Topic:
detection systems
R&D area:
R&D group:

Summary

Unlike current chemical trace detection technology, dogs actively sniff to acquire an odor sample. Flow visualization experiments with an anatomically-similar 3D printed dog's nose revealed the external aerodynamics during canine sniffing, where ventral-laterally expired air jets entrain odorant-laden air toward the nose, thereby extending the "aerodynamic reach" for inspiration of otherwise inaccessible odors. Chemical sampling and detection experiments quantified two modes of operation with the artificial nose-active sniffing and continuous inspiration-and demonstrated an increase in odorant detection by a factor of up to 18 for active sniffing. A 16-fold improvement in detection was demonstrated with a commercially-available explosives detector by applying this bio-inspired design principle and making the device "sniff" like a dog. These lessons learned from the dog may benefit the next-generation of vapor samplers for explosives, narcotics, pathogens, or even cancer, and could inform future bio-inspired designs for optimized sampling of odor plumes.
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Summary

Unlike current chemical trace detection technology, dogs actively sniff to acquire an odor sample. Flow visualization experiments with an anatomically-similar 3D printed dog's nose revealed the external aerodynamics during canine sniffing, where ventral-laterally expired air jets entrain odorant-laden air toward the nose, thereby extending the "aerodynamic reach" for inspiration of...

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Biomimetic sniffing improves the detection performance of a 3D printed nose of a dog and a commercial trace vapor detector

Development of a high-throughput microwave imaging system for concealed weapons detection

October 18, 2016
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Conference Paper
Author:
William F. Moulder
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Published in:
6th Int. Symp. on Phased Array Systems and Technology, PAST 2016, 18-21 October 2016.
Topic:
detection systems
R&D area:
R&D group:

Summary

A video-rate microwave imaging aperture for concealed threat detection can serve as a useful tool in securing crowded, high foot traffic environments. Realization of such a system presents two major technical challenges: 1) implementation of an electrically large antenna array for capture of a moving subject, and 2) fast image reconstruction on cost-effective computing hardware. This paper presents a hardware-efficient multistatic array design to address the former challenge, and a compatible fast imaging technique to address the latter. Prototype hardware which forms a partition of an imaging aperture is discussed. Using this hardware, it is shown that the proposed array design can be used to form high-fidelity 3D images, and that the presented image reconstruction technique can form an image of a human-sized domain in ≤ 0.1s with low cost computing hardware.
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Summary

A video-rate microwave imaging aperture for concealed threat detection can serve as a useful tool in securing crowded, high foot traffic environments. Realization of such a system presents two major technical challenges: 1) implementation of an electrically large antenna array for capture of a moving subject, and 2) fast image...

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Development of a high-throughput microwave imaging system for concealed weapons detection

Directly-deposited blocking filters for high-performance silicon x-ray detectors

July 1, 2016
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Conference Paper
Author:
Marshall W. Bautz
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Published in:
SPIE, Vol. 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray, July 2016, 99054C.
Topic:
detection systems
R&D area:
R&D group:

Summary

Silicon X-ray detectors often require blocking filters to mitigate noise and out-of-band signal from UV and visible backgrounds. Such filters must be thin to minimize X-ray absorption, so direct deposition of filter material on the detector entrance surface is an attractive approach to fabrication of robust filters. On the other hand, the soft (E < 1 keV) X-ray spectral resolution of the detector is sensitive to the charge collection efficiency in the immediate vicinity of its entrance surface, so it is important that any filter layer is deposited without disturbing the electric field distribution there. We have successfully deposited aluminum blocking filters, ranging in thickness from 70 to 220nm, on back-illuminated CCD X-ray detectors passivated by means of molecular beam epitaxy. Here we report measurements showing that directly deposited filters have little or no effect on soft X-ray spectral resolution. We also find that in applications requiring very large optical density (> OD 6) care must be taken to prevent light from entering the sides and mounting surfaces of the detector. Our methods have been used to deposit filters on the detectors of the REXIS instrument scheduled to fly on OSIRIS-ReX later this year.
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Summary

Silicon X-ray detectors often require blocking filters to mitigate noise and out-of-band signal from UV and visible backgrounds. Such filters must be thin to minimize X-ray absorption, so direct deposition of filter material on the detector entrance surface is an attractive approach to fabrication of robust filters. On the other...

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Directly-deposited blocking filters for high-performance silicon x-ray detectors

Reagent approaches for improved detection of chlorate and perchlorate salts via thermal desorption and ionization

January 15, 2016
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Journal Article
Author:
Jude A. Kelley
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Published in:
Rapid Commun. Mass Spectrom., Vol. 30, No. 1, 15 January 2016, pp. 191-8, DOI: 10.1002/rcm.7427.
Topic:
detection systems
R&D area:
R&D group:

Summary

RATIONALE: Techniques for improving the detectability of chlorate and perchlorate salts with thermal desorption based ionizers (i.e. radioactive, corona discharge and photoionization-based) are desired. This work employs acidic reagents to chemically transform chlorate and perchlorate anions into traces of chloric and perchloric acid. These high vapor pressure acids are easier to detect than the originating salts. METHODS: The efficacy of the reagent chemistry was quantified with a triple-quadrupole mass spectrometer interfaced with a custom-built thermal-desorption atmospheric-pressure chemical ionization (TD-APCI) source. Additional experiments were conducted using tandem IMS/MS instrumentation. Reagent pKa and pH values were varied in order to gain a better understanding of how those parameters affect the degree of observed signal enhancement. RESULTS: Samples of chlorates and perchlorates treated with liquid acidic reagents exhibit signal enhancement of up to six orders of magnitude compared with signals from untreated analytes. Three orders of magnitude of signal enhancement are demonstrated using solid-state reagents, such as weakly acidic salts and polymeric acids. Data is presented that demonstrates the compatibility of the solid-state approach with both MS and IMS/MS platforms. CONCLUSIONS: Several methods of acidification were demonstrated for enhanced vaporization and detection of chlorates and perchlorates. For applications where rapid surface collection and analysis for chlorates and perchlorates are desired, the solid-state approaches offer the simplest means to integrate the reagent chemistry into MS or IMS detection.
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Summary

RATIONALE: Techniques for improving the detectability of chlorate and perchlorate salts with thermal desorption based ionizers (i.e. radioactive, corona discharge and photoionization-based) are desired. This work employs acidic reagents to chemically transform chlorate and perchlorate anions into traces of chloric and perchloric acid. These high vapor pressure acids are easier...

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Reagent approaches for improved detection of chlorate and perchlorate salts via thermal desorption and ionization

Sensitive detection and identification of isovanillin aerosol particles at the pg/cm^3 mass concentration level using Raman spectroscopy

June 8, 2015
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Journal Article
Author:
Roshan L. Aggarwal
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Published in:
Aerosol Sci. Technol., Vol. 49, No. 9, 2015, pp. 753-6.
Topic:
detection systems
R&D area:
R&D group:

Summary

A compact Raman spectroscopy system with high sensitivity to chemical aerosols has been developed. This system has been used to detect isovanillin aerosols with mass concentration of 12 pg/cm3 in a 15 s signal integration period with a signal-to-noise ratio of 32. We believe this represents the lowest chemical aerosol concentration and signal integration period product ever reported for a Raman spectroscopy system. The Raman system includes (i) a 10 W, 532-nm cw laser, (ii) an aerosol flow cell, (iii) a 60x aerosol concentrator, (iv) an f/1.8 Raman spectrometer with a spectral range of 400-1400 cm^-1 and a resolution of 4 cm^-1, and (v) a low-noise CCD camera (1340 x 400 pixels). The collection efficiency of the Raman system has been determined to be 2.8%. Except for the laser cooling subsystem, the Raman system fits in a 0.61 m x 0.61 m x 0.61 m box.
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Summary

A compact Raman spectroscopy system with high sensitivity to chemical aerosols has been developed. This system has been used to detect isovanillin aerosols with mass concentration of 12 pg/cm3 in a 15 s signal integration period with a signal-to-noise ratio of 32. We believe this represents the lowest chemical aerosol...

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Sensitive detection and identification of isovanillin aerosol particles at the pg/cm^3 mass concentration level using Raman spectroscopy

Trace aerosol detection and identification by dynamic photoacoustic spectroscopy

December 15, 2014
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Journal Article
Author:
Ryan M. Sullenberger
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Published in:
Opt. Express, Vol. 22, No. 25, 15 December 2014, pp. A1810-A1817.
Topic:
detection systems
R&D area:
R&D group:

Summary

Dynamic photoacoustic spectroscopy (DPAS) is a high sensitivity technique for standoff detection of trace vapors. A field-portable DPAS system has potential as an early warning provider for gaseous-based chemical threats. For the first time, we utilize DPAS to successfully detect the presence of trace aerosols. Aerosol identification via long-wavelength infrared (LWIR) spectra is demonstrated. We estimate the sensitivity of our DPAS system to aerosols comprised of silica particles is comparable to that of SF6 gas based on a signal level per absorbance unit metric for the two materials. The implications of the measurements are discussed.
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Summary

Dynamic photoacoustic spectroscopy (DPAS) is a high sensitivity technique for standoff detection of trace vapors. A field-portable DPAS system has potential as an early warning provider for gaseous-based chemical threats. For the first time, we utilize DPAS to successfully detect the presence of trace aerosols. Aerosol identification via long-wavelength infrared...

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Trace aerosol detection and identification by dynamic photoacoustic spectroscopy

Detecting small asteroids with the Space Surveillance Telescope

September 1, 2014
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Journal Article
Author:
Jessica D. Ruprecht
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Published in:
Icarus, Vol. 239, 2014, pp. 253-9.
Topic:
space
R&D area:
R&D group:

Summary

The ability of the Space Surveillance Telescope (SST) to find small (2-15 m diameter) NEAs suitable for the NASA asteroid retrieval mission is investigated. Orbits from a simulated population of targetable small asteroids were propagated and observations with the SST were simulated. Different search patterns and telescope time allocation cases were considered, as well as losses due to FOV gaps and weather. It is concluded that a full-time, dedicated survey at the SST is likely necessary to find a useful population of these NEAs within the mission launch timeframe, especially if an object must be observed on >1 night at SST to qualify as a detection. The simulations were also performed for an identical telescope in the southern hemisphere, which is found to produce results very similar to the SST in New Mexico due to significant (~80%) overlap in the population of objects detected at each site. In addition to considering the SST's ability to detect small NEAs, a parallel study was performed focusing on >100 m diameter objects. This work shows that even with limited telescope time (3 nights per month) a substantial number of these larger objects would be detected.
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Summary

The ability of the Space Surveillance Telescope (SST) to find small (2-15 m diameter) NEAs suitable for the NASA asteroid retrieval mission is investigated. Orbits from a simulated population of targetable small asteroids were propagated and observations with the SST were simulated. Different search patterns and telescope time allocation cases...

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Detecting small asteroids with the Space Surveillance Telescope

Chemical aerosol detection and identification using Raman scattering

August 1, 2014
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Journal Article
Author:
Roshan L. Aggarwal
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Published in:
J. Raman Spectrosc., Vol. 45, No. 8, August 2014, pp. 677-9.
Topic:
detection systems
R&D area:
R&D group:

Summary

Early warning of the presence of chemical agent aerosols is an important component in the defense against such agents. A Raman spectrometer has been constructed for the purpose of detecting and identifying chemical aerosols. We report the detection and identification of a low-concentration chemical aerosol in atmospheric air using 532-nm continuous wave laser Raman scattering. We have demonstrated the Raman scattering detection and identification of an aerosol of isovanillin of mass concentration of 1.8 ng/cm^3 with a signal-to-noise ratio of about 19 in 30 s for the 116-cm^-1 mode with a Raman cross section of 3.3 x 10^-28 cm^2 using 8-W double-pass laser power.
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Summary

Early warning of the presence of chemical agent aerosols is an important component in the defense against such agents. A Raman spectrometer has been constructed for the purpose of detecting and identifying chemical aerosols. We report the detection and identification of a low-concentration chemical aerosol in atmospheric air using 532-nm...

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Chemical aerosol detection and identification using Raman scattering

Velocity estimation improvements for the ASR-9 Weather Systems Processor

February 2, 2014
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Conference Paper
Author:
James M. Kurdzo
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Published in:
American Meteorological Society Annual Meeting, 2-6 February 2014.
Topic:
algorithms
R&D area:
R&D group:

Summary

The Airport Surveillance Radar (ASR-9) is a rapid-scanning terminal aircraft detection system deployed at airports around the United States. To provide cost-effective wind shear detection capability at medium-density airports, the Weather Systems Processor (WSP) was developed and added on to the ASR-9 at 35 sites. The WSP on the ASR-9 is capable of utilizing dual fan-beam estimates of reflectivity and velocity in order to detect low-level features such as gust fronts, wind shear, and microbursts, which would normally be best detectable by a low-scanning pencil beam radar. An upgrade to the ASR-9 WSP, which is currently ongoing, allows for additional computational complexity in the front-end digital signal processing algorithms compared to previous iterations of the system. This paper will explore ideas for improving velocity estimates, including low-level dual beam weight estimation, de-aliasing, and noise reduction. A discussion of the unique challenges afforded by the ASR-9's block-stagger pulse repetition time is presented, along with thoughts on how to overcome limitations which arise from rapid-scanning and the inherent lack of pulses available for coherent averaging.
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Summary

The Airport Surveillance Radar (ASR-9) is a rapid-scanning terminal aircraft detection system deployed at airports around the United States. To provide cost-effective wind shear detection capability at medium-density airports, the Weather Systems Processor (WSP) was developed and added on to the ASR-9 at 35 sites. The WSP on the ASR-9...

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Velocity estimation improvements for the ASR-9 Weather Systems Processor
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