Patent Application
20110027899
Various embodiments of the invention pertain to a detection method for detection of trace quantities of explosive components including nitrates, oxidizers and peroxides, or other radical-generating agents.
An explosive material is a material that either is chemically or otherwise energetically unstable or produces a sudden expansion of the material usually accompanied by the production of heat and large changes in pressure (and typically also a flash and/or loud noise) upon ignition. Examples of explosive compounds include, but are not limited to ammonium nitrate, nitroglycerin, acetone peroxide, trinitrotoluene (TNT), nitrocellulose, RDX, PETN, and HMX. Recently, the detection of explosives in venues such as ports (which serve as the entry point for importing foreign commodities), airports and other border entries, has become extremely important in view of the global spread of terrorist attacks.
The detection of explosive compound residues has been attempted with mass spectroscopy, fluorescence detection, and nitric oxide detection. Mass spectroscopy requires expensive and cumbersome equipment that needs frequent maintenance. Fluorescence detection may not be sensitive enough for all applications, and requires that samples be accessible to sampling by wipes that are then irradiated to detect any residue. Nitrogen monoxide detection has been developed based on the principle that many explosives can be made to generate nitrogen monoxides. Conventional equipment used in these techniques is relatively insensitive, requires frequent calibration and service, and/or does not detect all of the possible types of explosives.
In high traffic areas such as airports, cargo terminals and ports, the presence of an explosive device can be difficult to detect. An explosive device can be hidden on an individual or within cargo filled with legal and traceable imported goods. Airports and cargo terminals often use X-ray and CAT equipment to rapidly scan large numbers of items (e.g., shipping boxes) in an attempt to identify items that could contain explosives. These methods require highly trained operators, and the quality of detection is dependent on the skill of the operator. If something suspicious is preliminarily detected, it is still not certain that it is a bomb until it is removed from inside the package and examined.
Consequently, a method, system or apparatus which cures the deficiencies as described previously is desirable.
A method for detecting explosive compounds, comprising: (a) collecting an air sample in a vicinity of an object; (b) subjecting the air sample to one of heat or irradiation to generate nitrogen dioxide (NO2); and (c) measuring the generated nitrogen dioxide (NO2) by a nitrogen dioxide detector is herein disclosed. For nitrogen-containing explosive compounds which preferentially decompose to nitrogen monoxide (NO), the method may further comprise (d) converting the generated nitrogen monoxide (NO) to nitrogen dioxide (NO2) by gas phase titration. The gas phase titration may comprise: (i) exposing the air sample to ozone; and (ii) allowing the air sample to remain in a heated reaction chamber for a predetermined amount of time. For non-nitrogen-containing explosive compounds, the method may further comprise (e) adding nitrogen monoxide (NO) to the air sample stream during subjecting the air sample to one of heat or irradiation.
Collecting an air sample may comprise one of mechanically transporting a collected sample to an instrument, vacuum collection of vapor or particles, and vortex vacuum sampling. Subjecting the air sample to one of heat or irradiation may comprise heating the sample to between 150 degrees Celsius and 300 degrees Celsius. After collecting an air sample, the air sample may be introduced into a gas scrubber mechanism. Furthermore, after introducing the air sample into the gas scrubber mechanism, the air sample may be introduced into a cyclone. Furthermore, after introducing the air sample into the cyclone, the air sample may be introduced into a thermolysis heater. Furthermore, after introducing the air sample into the thermolysis heater, the air sample may be introduced into a nitrogen dioxide analyzer. The nitrogen dioxide analyzer may be one of a cavity attenuated ring down spectrometer with gated integrated detection (CARDS-GID), a cavity phase shift spectroscopy (CAPS)-based instrument, a cavity enhanced absorption analyzer (CEAS), or a laser-induced fluorescence detector (LIF). During subjecting the air sample, adding carbon monoxide (CO) or a hydrogen-containing organic compound to the sample stream may enhance the conversion of nitrogen monoxide (NO) to nitrogen dioxide (NO2).
A system for detecting explosive compounds, comprising: (a) an inlet for taking in an air sample; (b) at least one filter mechanism in fluid communication with the inlet; (c) one of a heater or radiation device in fluid communication with the at least one filter mechanism; and (d) a nitrogen dioxide analyzer in communication with the heater or radiation device is herein disclosed. The system may further comprise (e) a gas titration system in fluid communication with the system for detecting explosive compounds, the gas titration system comprising: (f) an ozone generator; and (g) a heated reaction chamber in fluid communication with the ozone generator wherein the heated reaction chamber includes a plurality of glass beads.
The system may further comprise a nitrogen monoxide (NO) source in fluid communication with the system for detecting explosive compounds. The system may further comprise a carbon monoxide (CO) or a hydrogen-containing organic compound source in fluid communication with the system for detecting explosive compounds. The hydrogen-containing organic compound may be, e.g., isopropyl alcohol. The nitrogen dioxide analyzer may be one of a cavity attenuated ring down spectrometer with gated integrated detection (CARDS-GID), a cavity phase shift spectroscopy (CAPS)-based instrument, cavity enhanced absorption (CEAS) or a laser-induced fluorescence detector (LIF). The system may further comprise a cyclone device in fluid communication between the at least one filter mechanism and the heater or radiation device. The heater or radiation device may be a thermolysis heater.
In the following description numerous specific details are set forth in order to provide a thorough understanding of the invention. However, one skilled in the art would recognize that the invention might be practiced without these specific details. In other instances, well known methods, procedures, and/or components have not been described in detail so as not to unnecessarily obscure aspects of the invention.
Embodiments of the invention are directed to an apparatus and method for detecting explosive compounds by air sampling followed by subjecting the air sample to a detection method. In one embodiment, a test area (including, but not limited to, an area about a person or an object) is sampled by drawing air from the vicinity of the test area, heating or irradiating the air sample and subjecting the irradiated sample to a detection method. With respect to some nitrogen-containing explosive compounds, heating or irradiating the air sample produces nitrogen dioxide (NO2). With respect to some non-nitrogen-containing explosive compounds (e.g., oxygen-containing explosive compounds), the air sample may be exposed to a source of nitrogen monoxide (NO) to generate nitrogen dioxide (NO2). With respect to nitrogen-containing samples that preferentially generate nitrogen monoxide (NO) rather than nitrogen dioxide (NO2), gas titration may be integrated into the system to convert nitrogen monoxide (NO) to nitrogen dioxide (NO2). The resultant nitrogen dioxide (NO2) may be detected by a nitrogen dioxide analyzer (“NO2-analyzer”) by a device such as, but not limited to, a cavity attenuated ring down spectrometer with gated integrated detection (CARDS-GID), a cavity phase shift spectroscopy (CAPS)-based instrument, or a laser-induced fluorescence detector (LIF).
Next, the air sample may be introduced into a cyclone 304 which works by creating a vortex where heavier particles, such as mineral dust, dirt, or pollen, strike the walls of cyclone 304 and fall into a cup (not shown) to be subsequently removed. Next, the air sample may be introduced into a thermolysis heater 306 (see
Because not all explosive compounds are nitrogen-containing, modifications to the system previously describe may be required. Oxidizers and peroxides are also components of explosives that may be desirable to detect. Such compounds may be detected by the same apparatus/method described previously by adding nitrogen dioxide (NO) to the sample stream and measuring the generated nitrogen dioxide (NO2). For example, in one embodiment, the air sample may be exposed to a source of nitrogen monoxide (NO) so that the presence of non-nitrogen-containing explosive compounds, e.g., oxidizers or peroxides, can be detected by the reaction of such compounds with nitrogen monoxide (NO) to produce nitrogen dioxide (NO2). The resultant nitrogen dioxide (NO2), if any, is proportional to non-nitrogen-containing explosive particles, if present, and may be subsequently by detected by the NO2-analyzer. In another embodiment, a radical chain-propagating species such as carbon monoxide (CO), isopropyl alcohol (C3H7OH), or any other suitable hydrocarbon may be added in addition to nitrogen monoxide (NO) to enhance the resulting signal of nitrogen dioxide (NO2) (see
Some explosive compounds, such as TNT, preferentially generate nitrogen monoxide (NO) (rather than nitrogen dioxide) and can then be detected by thermal generation of nitrogen monoxide (NO), conversion of nitrogen monoxide (NO) to nitrogen dioxide (NO2) by gas phase titration, and detection of the resulting nitrogen dioxide (NO2).
Embodiments of the system as described previously have several advantages over conventional systems used to detect explosive materials. Unlike mass spectroscopy, the CRDS analyzer is simple and relatively inexpensive. CRDS does not need calibration or frequent maintenance. More types of explosives can be detected than with an NO2-analyzer and the detection sensitivity is higher.
One or more of the components and functions illustrated in the figures may be rearranged and/or combined into a single component or embodied in several components without departing from the invention. Additional elements or components may also be added without departing from the invention. The apparatus, devices, and/or components illustrated in the figures may be configured to perform the methods, features, or steps illustrated in
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications are possible. Those skilled, in the art will appreciate that various adaptations and modifications of the just described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
This application claims priority to U.S. App. Ser. No. 61/151,320 filed Feb. 10, 2009 and hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61151320 | Feb 2009 | US |
