WO2010095123A1

WO2010095123A1 - Methods for detection of explosives by use of vapour markers

Info

Publication number: WO2010095123A1
Application number: PCT/IL2009/001194
Authority: WO
Inventors: Marian Langford; Zamir Eldar; Gabriel Vago; Oren Sapir
Original assignee: Icts Europe Holdings B.V.
Priority date: 2009-02-19
Filing date: 2009-12-16
Publication date: 2010-08-26
Also published as: IL197142A0

Abstract

A method for detecting presence of explosives in cargo, the method comprising a candidate identification stage: analyzing vapours present in a vicinity of each explosive sample, thereby to identify a candidate explosive marker vapour; in a candidate evaluation stage, analyzing vapours present in a vicinity of each non-explosive cargo sample and determining a frequency of occurrence of the candidate explosive marker in the non-explosive cargo samples; analyzing vapours present in a vicinity of the cargo, thereby to identify a marker vapour; and alerting to presence of explosives, if at least one marker vapour is identified by the analyzing, wherein the marker vapour comprises a candidate explosive marker vapour from among those identified in the candidate identification stage which was found, in the candidate evaluation stage, to have an acceptably low frequency of occurrence.

Description

METHODS FOR DETECTION OF EXPLOSIVES BY USE OF VAPOUR MARKERS

REFERENCE TO CO-PENDING APPLICATIONS

Reference is made to co-pending United States Patent Application No. 10/677,225, filed 10/03/2003 and entitled "Method and apparatus for detecting substance to be detected containing at least one component that is dispersible in air in the form of solid particles".

FIELD OF THE INVENTION

The present invention relates generally to detection of undesirable substances and more particularly to detection of undesirable substances in cargo.

BACKGROUND OF THE INVENTION

Conventional technology pertaining to certain embodiments of the present invention is described in the following publications inter alia:

Harper, Ross J. et al, "Identification of dominant odour chemicals emanating from explosives for use in developing optimal training aid combinations and mimics for canine detection", Talanta 67 (2005), 313-327;

"Electronic hose could spark end of sniffer dogs", CNN.com, 1 August 2008 and the following United States patents and published patent applications:

BACKGROUND OF THE INVENTION

Bulk explosive detectors utilize a variety of different technologies to detect explosive material including X-ray imaging, quadrupole resonance, infrared and millimetre wave imaging and various neutron techniques. Trace explosive detection deals with the detection of tiny amounts of explosive that indicate that a larger mass is present or has passed through the environment. It is further divided into vapour detection and trace particle detection. Vapour detection is the detection of vapours, consisting of free atoms and/or molecules, emitted by explosive. Trace particle detection is the detection of a conglomerate of atoms and/or molecules or the adsorption of vapours onto natural particles such as dust. These particles are not usually visible to the eye and the explosive component has a tiny but detectable mass. Generally these particles are found on surfaces and are left behind after explosive has been handled in, or passed through, the environment. However, on occasion, some of these particles are small enough to be suspended in air. Commercially available trace detectors include the Smiths IonScan (trace particle), the Sabre (trace particle and vapour), the GE Itemizer3 (trace particle) and the VaporTracer (trace particle and vapour).

United States Patent 5585575, entitled "Explosive detection screening system" and assigned to Research Corporation Technologies, Inc., describes an explosive detection screening system used for the detection of explosives and other controlled substances such as drugs or narcotics. The screening system detects the vapour and/or particulate emissions from the aforementioned substances and reports that they are present on an individual or object and the concentration of each substance detected. The screening system comprises a sampling chamber for the collection of the vapour and/or particulate emissions, a concentration and analyzing system for the purification of the collected vapour and/or particulate emissions and subsequent detailed chemical analysis of the emissions, and a control and data processing system for the control of the overall system.

United States Patent 5859362, entitled "Trace vapour detection" and assigned to Revenue Canada, describes a method and device for the detection of vapours of cocaine and associated compounds are disclosed. The method involves sampling a volume of air suspected of containing cocaine vapours, passing this air through a filtration system that removes any particulate matter and binds vapours of cocaine and associated compounds, if present, for further analysis. A preferred associated compound-vapour is that of ecgonidine methyl ester (EDME), which is a component of street cocaine being produced by thermal decomposition of cocaine and which is considered an indicator for the presence of cocaine. The device is comprised of a sampling, filtration and vacuum port components and can be easily attached to a container, and suction source, for the sampling of air.

United States Patent 4987767, entitled "Explosive detection screening system" and assigned to Research Corporation Technologies, Inc., describes an explosive detection screening system used for the detection of explosives and other controlled substances such as drugs or narcotics. The screening system detects the vapour and/or particulate emissions from the aforementioned substances and reports that they are present on an individual or object and the concentration of each substance detected. The screening system comprises a sampling chamber for the collection of the vapour and/or particulate emissions, a concentration and analyzing system for the purification of the collected vapour and/or particulate emissions and subsequent detailed chemical analysis of the emissions, and a control and data processing system for the control of the overall system.

Other publications indicative of the state of the art include:

Vapour and Trace Detection of Explosives for Anti-Terrorism Purposes. Proceedings of the NATO Advanced Research Workshop, held in Moscow, Russia, 19-20 March 2003. Series: NATO Science Series II: Mathematics, Physics and Chemistry , Vol. 167. Krause, M. (Ed.), 2004. Forensic and Environmental Detection of Explosives, Jehuda Yinon, ISBN: 978-0-471- 98371-2, Wiley, July 1999.

Electronic Noses and Sensors for the Detection of Explosives. Proceedings of the NATO Advanced Research Workshop, held in Warwick, Coventry, U.K., 30 September-3 October 2003. Series: NATO Science Series II: Mathematics, Physics and Chemistry , Vol. 159. Gardner, J.; Yinon, Jehuda (Eds.) 2004, XVII, ISBN: 978-1-4020-2318-7.

The disclosures of all publications and patent documents mentioned in the specification, and of the publications and patent documents cited therein directly or indirectly, are hereby incorporated by reference.

SUMMARY OF THE INVENTION

Certain embodiments of the present invention seek to provide improved methods for identifying undesirable substances, such as explosives, in cargo.

RASCargO is a canine cargo screening system which uses a remote method of canine inspection. Vapour samples are collected from cargo pallets/trucks on special filters. These filters are subsequently screened by the dogs for explosive vapours using a RASCO (Remote Air Sampling Canine Olfaction) technique.

It is an object of certain embodiments of the present invention to provide a vapour detector that can be used to replace the dogs in the RASCargO system.

Explosives have very complex scents. Most explosive materials consist of an explosive substance e.g. RDX crystals (the explosive component) mixed with a variety of other materials. A few explosive materials e.g. cast TNT consist entirely or primarily of the explosive component. However, even these latter materials contain contaminants and by-products produced or introduced during manufacture.

The complex scents generated by explosive are from the explosive component, the chemicals used in the manufacture of the explosive component and scents from all the materials that are mixed with the explosive component e.g. dyes, stabilisers, materials used in manufacture thereof, and/or contaminants introduced during manufacture, use and/of storage thereof. In addition, explosives absorb vapours from the environment and then re-emit these vapours. Thus, the scent of explosive is very complicated and not intuitive. Conventional explosive detectors detect explosive by looking for the actual explosive material, for example, Cyclotrimethylenetrinitramine (RDX) in the case of C4 explosive. This has not been a successful stratagem and no vapour detector has so far been developed that can detect RDX and Pentaerythritol tetranitrate (PETN) vapour at their ambient vapour pressures. In contrast, it seems likely that dogs learn the scent signature of explosive which may comprise several key vapours and it is possible that none of these are produced by the explosive component itself.

According to certain embodiments of the present invention, a learning stage is provided in which a system learns which vapours are commonly present in explosive headspace. This learning stage leads to the identification of a list of marker vapours that are characteristic of explosive headspace - but are not necessarily vapours produced by the explosive component itself. A machine is then used to detect all of the marker vapours simultaneously.

In the learning stage, vapour headspace samples may be collected from above a wide variety of explosive materials in controlled conditions. Typically, many samples are collected from different types of explosive and from explosives from different sources which have been stored in different places. These samples are subsequently chemically analysed using standard commercial analysis equipment e.g. a gas chromatography - mass spectrometry (GC-MS) analyser. It is appreciated that analysis as above discloses that some explosive materials produce vapours associated with the explosive component, some explosives produce vapours associated with chemicals that are used in the manufacture of the explosive component, some explosives produce vapours associated with materials that have been mixed with the explosive component, some explosives produce vapours known as "contaminant vapours" that are associated with other explosives or materials that they have been stored with, and, in extreme cases, some explosives do not produce any major detectable vapour from their own material; instead the entire detected spectrum is made up of contaminant vapours.

It is believed that hermetically sealed explosive retains its own vapours, whereas non- hermetically wrapped/stored explosive loses its vapours over time. These lost vapours percolate into the atmosphere of the explosives store or other storage environment. Badly wrapped/stored explosive also gain vapours from the environment. In summary, over time, badly wrapped/stored explosives lose their own scents and gain scents from the environment at the same time. The resulting "contaminant marker substances" are distinctive and almost certainly help the dogs to detect explosive.

Methods for determining explosive markers are described hereinbelow. Studies performed in accordance with these methods allowed a set of suitable vapour markers as described hereinbelow, to be developed. The list does not include all possible markers and therefore is not intended to be limiting. By analyzing other explosive headspace vapours using methods shown and described herein, it is likely that the set of marker vapours may be extended to contain other marker vapours. According to certain embodiments of the present invention, the above set of explosive marker vapours may be used in the following method:

Step 1 — Collection of vapours in ambient conditions from cargo, or bags or vehicles using suitable vapour collectors.

Step 2 -Transporting samples to another location and maintaining until testing can be carried out

Step 3 - Testing samples for the presence of the marker vapours in the above marker set, using a suitable spectrometer which may optionally be modified in accordance with the teachings of the present invention, and alarming for explosive presence in individual samples accordingly. One example of a suitable spectrometer, which is not intended to be limiting, is the Scentinel, a commercially available tandem mass spectrometer developed by a consortium including Mass Spec Analytical Ltd of Bristol, UK, MDS Sciex Inc. of Toronto, Canada and J.S. Chinn P.E. Ltd of Bristol, UK.

Regarding step 1 , vapour samples may be collected by using a vapour collector to suck air from pallets, boxes, trucks or containers or other volumes or regions of interest and passing the air through a filter containing a sorbent material. Air is typically sucked through the filter at a rate of 40-70 litres/min by a mobile trolley mounted pump powered by battery or cable. Personnel are warned not to carry out any action which might allow the ingress/exchange of air before samples are collected. The vapour collector, also termed a "sampler", has a solid probe which is pushed through pallet/box/item wrappings or through a gap or door seals into a container. In those cases where there is no suitable wrapping, personnel wrap the item and leave it to equilibrate for a suitable period of time, such as (for certain applications), 2 hours or more. If required, items may be sampled more than once and from more than one position but alternatively, only one sample may be collected from each item. To achieve contamination control, staff handling filters change disposable gloves every sample and the probe is also regularly changed.

Regarding step 2, the filters are removed from the sampler and each filter is placed in a separate labelled and sealed container.

Regarding step 3, each filter may be placed into a custom made desorber coupled to a suitable analyser such as an ion trap or a tandem mass spectrometer such as that manufactured by MDS Sciex Inc. Each filter is heated rapidly so that its vapours are given up in a fast pulse. The vapours pass through an inlet into an ionization chamber where atoms/molecules are ionized. A tandem mass spectrometer contains two radio frequency quadrapole filters separated by a collision cell. The first quadrupole filter is pre-set to only pass ions characteristic of the marker vapours. The marker ions pass to the collision cell where they collide with the walls and a collision gas to produce fragment (daughter) ions. The second quadrupole filter is pre-set to only pass daughter ions characteristic of the marker vapours. In particular, each primary ion is specifically linked to a particular daughter ion by a time window. This relationship produces ion pairs where only a specific primary ion that produces a specific daughter ion is recognized as an important datum. Each marker vapour is identified with high confidence by one or more 'ion pairs'.

There is thus provided, in accordance with an embodiment of the present invention, a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in the vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if Cyclohexanone vapour is identified by the analyzing.

Also provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if DPA vapour is identified by the analyzing.

Further provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if EGDN vapour is identified by the analyzing.

Also provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if DMNB vapour is identified by the analyzing.

Additionally provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if NG vapour is identified by the analyzing.

Further provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if DNT vapour is identified by the analyzing. Additionally provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if TNT vapour is identified by the analyzing.

Also provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if Triacetin vapour is identified by the analyzing.

Also provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if 2-ethyl hexanol vapour is identified by the analyzing.

Also provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if Benzoquinone vapour is identified by the analyzing.

Still further in accordance with an embodiment of the present invention, the alerting comprises alerting to presence of explosives, when at least one of the following set of vapours is identified by the analyzing: Cyclohexanone, Benzoquinone, 2-ethyl hexanol, Triacetin, DPA, EGDN, DMNB, NG, DNT, and TNT.

Also provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify at least one marker vapour; and alerting to presence of explosives, if a marker vapour is identified by the analyzing.

Also provided, in accordance with an embodiment of the present invention, is a method for detecting the presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify and to alert to presence of explosives, if a predetermined group of marker vapours are identified by the analyzing.

Also provided, in accordance with an embodiment of the present invention, is a method for detecting the presence of explosives in cargo, the method comprising analyzing vapours present in a vicinity of the cargo, thereby to identify and to alert to presence of explosives, if a predetermined group of marker vapours with predetermined relative intensities are identified by the analyzing. Also provided, in accordance with an embodiment of the present invention, is a method for detecting presence of explosives in cargo, the method comprising in a candidate identification stage, analyzing vapours present in a vicinity of each of a first plurality of explosive samples, thereby to identify at least one candidate explosive marker vapour; in a candidate evaluation stage, analyzing vapours present in a vicinity of each of a second plurality of non-explosive cargo samples and determining a frequency of occurrence of the at least one candidate explosive marker in the second plurality of non-explosive cargo samples; analyzing vapours present in a vicinity of the cargo, thereby to identify at least one marker vapour; and alerting to presence of explosives, if at least one marker vapour is identified by the analyzing, wherein the marker vapour comprises a candidate explosive marker vapour from among those identified in the candidate identification stage which was found, in the candidate evaluation stage, to have an acceptably low frequency of occurrence in non-explosive cargo samples.

Still further in accordance with an embodiment of the present invention, the second plurality of non-explosive cargo samples are culled from different environments characterized by different contaminants.

Also provided, in accordance with an embodiment of the present invention, is a system for detecting the presence of explosives in cargo, the system comprising a vapour analyzer which is operative to analyze vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and a marker-vapour triggered explosives alarm operative to alert to presence of explosives, if at least one marker vapour is identified by the analyzing, wherein the marker vapour comprises a marker vapour, which tends to be present in cargo containing explosives and tends to be absent in cargo not containing explosives.

Further in accordance with an embodiment of the present invention, the identifying comprises identifying more than a pre-set threshold amount of the vapour.

In accordance with an embodiment of the present invention, the candidate explosive marker vapour comprises a vapour emitted by an explosive component.

Additionally in accordance with an embodiment of the present invention, the candidate explosive marker vapour comprises a vapour emitted by a chemical used to manufacture an explosive component. Further in accordance with an embodiment of the present invention, the candidate explosive marker vapour comprises a vapour emitted by an additive added in the course of manufacture of an explosive.

Further in accordance with an embodiment of the present invention, the candidate explosive marker vapour comprises a vapour absorbed and then re-emitted by an explosive material. Still further in accordance with an embodiment of the present invention, the candidate explosive marker vapour comprises a vapour previously exuded by an explosive material, subsequently absorbed by another explosive material, and then re-emitted.

Still further in accordance with an embodiment of the present invention, the candidate explosive marker vapour comprises a vapour previously exuded by an non-explosive material, and subsequently absorbed, by an explosive material and then re-emitted.

Additionally in accordance with an embodiment of the present invention, the candidate explosive marker vapour comprises a vapour emitted by a chemical used to manufacture explosives.

Still further in accordance with an embodiment of the present invention, the marker- vapour triggered explosives alarm is operative to alert to presence of explosives, if at least one marker vapour is identified by the analyzer, wherein the marker vapour comprises a vapour from an explosive that is a contaminant vapour in the explosive that is found in the cargo.

Additionally in accordance with an embodiment of the present invention, the analyzing comprises collecting samples from the cargo; transporting the samples to a analyzer disposed at a distance from the cargo; and using the analyzer to analyze the samples.

Further in accordance with an embodiment of the present invention, the collecting comprises sucking air containing vapours out of the cargo and through vapour collection filters, at each of a plurality of cargo sampling positions.

Further in accordance with an embodiment of the present invention, the candidate explosive marker vapour comprises a vapour exuded by explosive.

Further in accordance with an embodiment of the present invention, the vapour analyzer comprises at least one vapour collection filter; and apparatus for sucking air out of cargo and through the vapour collection filter.

Still further in accordance with an embodiment of the present invention, the vapour analyzer also comprises a spectrometer set up to automatically detect pre-selected vapour markers including all of: Cyclohexanone, Benzoquinone, 2-ethyl hexanol, Triacetin , DPA, EGDN, DMNB, NG, DNT, and TNT.

Further in accordance with an embodiment of the present invention, at each of the plurality of cargo sampling positions, air containing vapours are sucked through at least a pair of vapour collection filters, and the analyzing comprises analyzing one filter in each pair in positive ionization mode and another filter in each pair in negative ionization mode.

Any suitable processor, display and input means may be used to process, display, store and accept information, including computer programs, in accordance with some or all of the teachings of the present invention, such as but not limited to a conventional personal computer processor, workstation or other programmable device or computer or electronic computing device, either general-purpose or specifically constructed, for processing; a display screen and/or printer and/or speaker for displaying; machine-readable memory such as optical disks, CDROMs, magnetic-optical discs or other discs; RAMs, ROMs, EPROMs, EEPROMs, magnetic or optical or other cards, for storing, and keyboard or mouse for accepting. The term "process" as used above is intended to include any type of computation or manipulation or transformation of data represented as physical, e.g. electronic, phenomena which may occur or reside e.g. within registers and /or memories of a computer.

The above devices may communicate via any conventional wired or wireless digital communication means, e.g. via a wired or cellular telephone network or a computer network such as the Internet.

The apparatus of the present invention may include, according to certain embodiments of the invention, machine readable memory containing or otherwise storing a program of instructions which, when executed by the machine, implements some or all of the apparatus, methods, features and functionalities of the invention shown and described herein. Alternatively or in addition, the apparatus of the present invention may include, according to certain embodiments of the invention, a program as above which may be written in any conventional programming language, and optionally a machine for executing the program such as but not limited to a general purpose computer which may optionally be configured or activated in accordance with the teachings of the present invention.

The embodiments referred to above, and other embodiments, are described in detail in the next section.

Any trademark occurring in the text or drawings is the property of its owner and occurs herein merely to explain or illustrate one example of how an embodiment of the invention may be implemented.

Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions, utilizing terms such as, "processing", "computing", "estimating", "selecting", "ranking", "grading", "calculating", "determining", "generating", "reassessing", "classifying", "generating", "producing", "stereo-matching", "registering", "detecting", "associating", "superimposing", "obtaining" or the like, refer to the action and/or processes of a computer or computing system, or processor or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities within the computing system's registers and/or memories, into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices.

The following terms may be construed either in accordance with any definition thereof appearing in the prior art literature or in accordance with the specification, or as follows:

Remote method: The cargo is sampled in one position using filters to collect the vapours. The filters are removed to another place - the analysis room - where they are analyzed e.g. by dogs. Thus the analysis and potential the detection of explosives takes place remote from the cargo where the threat may be.

Vapour headspace sample: Vapours are emitted from virtually all materials and gather in the space around the object. If this space is closed, then the vapours increase in the enclosed volume, moving towards equilibrium. This enclosed space around the object is called the headspace.

Equilibrium: If an object is placed in a container and left at ambient temperatures for a period then "equilibrium" is said to have been reached when the vapours from the object in the headspace are in balance with the source of the vapours in the object and with any processes removing vapours.

Spectrum: In this context, tandem mass spectrometry spectrum or a GC-MS (gas chromatography/mass spectrometry) spectrum. A tandem mass spectrometry (tandem-MS) spectrum is essentially a graph of intensity versus ion mass/charge ratio. The spectrometer is set to only pass ions of pre-programmed mass/charge ratios (called m/z). Likewise a GC-MS spectrum is also a graph of intensity versus ion mass/charge ratio but obtained using a different analytical technique.

GC: Gas chromatography separates molecules in a mixture which then pass through a heated 'column' comprising a long but very small diameter tube. The sample is injected onto the top of the column and is driven through by a gas. As the sample passes through the column it separates into all its different component molecules and so different molecule types exit the column at different times. The GC spectrum records the intensity of the exiting molecules versus the time of exit producing a spectrum over a period of time.

GC-MS: In a GC-MS system, exiting molecules are ionized and fragmented. The fragment ions are detected and shown in a spectrum that shows intensity of a given ion versus the mass/charge of that ion. At each instant of time a complex MS spectrum is obtained for each molecular type exiting the column. This enables the molecule to be identified.

Filters: A vapour trap containing sorbent material.

C4 (or: C -4): A US manufactured plastic explosive. BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the present invention are illustrated in the following drawings:

Fig. 1 is a table of explosive materials tested to determine vapours produced.

Fig. 2A illustrate certain aspects of a GC-MS spectra of the plastic explosive C4 and specifically the intensity spectrum of the selected ion 46 m/z.

Fig. 2B illustrate certain aspects of a GC-MS spectra of the plastic explosive C4 and specifically the total ion count spectrum.

Fig. 3 A illustrate certain aspects of a GC-MS spectra of TNT flake and specifically the intensity spectrum of the selected ion 46 m/z.

Fig. 3 B illustrate certain aspects of a GC-MS spectra of TNT flake and specifically the total ion count spectrum.

Fig. 4 is a table of marker vapours useful in detecting hidden explosives according to certain embodiments of the present invention.

Fig. 5 is a simplified flowchart illustration of successful detection of explosive e.g. using the marker vapours of Fig. 4.

DETAILED DESCRIPTION OF EMBODIMENTS

Methods for determining which marker vapours to use in order to successfully detect concealed explosive are described herein, as well as methods for validating the effectiveness of such marker vapours.

Methods for identifying explosive marker vapours are now described. A wide variety of explosive materials were gathered from a wide variety of sources and were tested to determine the full range of vapours that they produce. In all, 28 types of explosives, crystals and powders were tested e.g. those listed in the table of Fig. 1.

In addition, some common explosive materials such as TNT were collected from different sources in three different countries in order to evaluate the effect that different storage environments might have on the vapours emitted by explosive.

All explosive samples were allowed to individually equilibrate in sealed low vapour nylon bags for 1-2 hours at ambient temperatures. The vapours were collected by inserting a stainless steel sorbent tube packed with Tenax TA sorbent coupled to a 1 litre syringe into the sealed bag containing the explosive and drawing 1 litre of air through the Tenax tube. The vapour samples were analysed using gas chromatography - mass spectrometry (GC-MS) equipment. This analysis was used to produce a list of vapours that were identified in the headspace vapour of each explosive sample. The data from all of the headspace vapour analyses of all samples of explosive material were studied and compared. It was sought to identify volatile vapours that were common to explosive materials.

Headspace analysis using standard analytical techniques is not sensitive enough to detect key explosive materials such as RDX and PETN. RDX and PETN form the basis of many important threat materials such as C4, Semtex, Hexilene, Plastrite, PE4, Demex and many other RDX based and/or PETN based plastic explosives. These plastic explosives are considered key threat materials by government agencies. However, there were other volatile vapours in the headspace from these explosives that were common to the headspace of explosive materials.

Figs. 2A - 2B show the result of a GC-MS analysis of the headspace vapour of a relatively newly purchased piece of C4. Fig. 2B is the total ion count (TIC) and shows that the two markers DMNB and 2-EH were easily detected. Fig. 2 A shows the intensity of the selected ion 46 m/z. This is a more sensitive way of looking for nitrates and shows that EGDN is also present in the headspace. The primary use of 2-ethylhexanol is in the manufacture of the plasticizer diester bis(2-ethylhexyl) phthalate (DEHP) and phthalates are the most commonly used plasticizers in the world. Thus it is likely that 2-EH is produced by the plasticizers in the explosive. DMNB is added as a taggant to plastic explosive during manufacture at the level of 1%. EGDN, is a vapour contaminant, probably picked up in the explosives store.

Headspace analysis of Dynamite and TNT based explosive demonstrated that explosive components of Dynamite (nitroglycerine and EGDN) and TNT (TNT and DNT) were detectable in the headspace, frequently along with marker vapours. Figs. 3 A - 3B show the result of a GC- MS analysis of relatively recently purchased TNT flake. Fig. 3B is the total ion count and shows that TNT, DMNB and several isomers of DNT were easily detected. Fig. 3 A shows the intensity of the selected ion 46m/z which shows that EGDN is also present in the headspace. TNT is the vapour from the explosive component, isomers of DNT are produced as a by-product in the manufacture of TNT, DMNB and EGDN are both vapour contaminants in this explosive.

A list of marker vapours was compiled using the data from the headspace analysis of vapours emitted by the wide variety of explosive materials analysed. These vapours are thought to become associated with explosive material through the following mechanisms:

• Vapour associated with a material used in the manufacture of the explosive component e.g. cyclohexanone which is used in the recrystallisation of RDX crystals.

• Vapour associated with a material added to the explosive component e.g. plasticizers, stabilisers, binders, dyes etc. • Vapour emitted by an explosive component within the explosive e.g. nitroglycerin is the main component of Dynamite and is emitted by Dynamite explosive

• Vapour contamination absorbed from the environment and re-emitted. Note. All explosive emits vapour over time, especially if it is badly wrapped. In explosive stores, vapours are emitted from explosives into the store atmosphere. Vapours from the atmosphere are then absorbed by the explosives in the store. This leads to a gradual mixing of vapour signatures as explosive becomes contaminated. As an example, an explosive that does not contain nitroglycerin e.g. Semtex will start to emit nitroglycerin if it has been stored with Dynamite and has become vapour contaminated.

After a full analysis the set of markers appearing in Fig. 4 was compiled. It is appreciated that the order and arrangement of markers in the table of Fig. 4 does not have any particular significance. Using the methods of the present invention, other marker vapours may be identified.

Methods for detecting concealed explosives using the marker vapours of Fig. 4, and for validating the effectiveness thereof, are now described.

In order to successfully use a list of marker vapours to detect explosive, a detection instrument is typically used which is capable of looking for several different markers at the same time and filtering out background signals from non-marker vapours.

The following embodiments of the invention were carried out using the Scentinel detector produced by Mass Spec Analytical Ltd. The Scentinel is a commercially available trace and vapour detection system developed by a consortium including Mass Spec Analytical Ltd (MSA) of Bristol, UK, MDS Sciex Inc. of Toronto, Canada and J.S. Chinn P.E. Ltd of Bristol, UK. The Scentinel system comprises a front end desorber designed by MSA coupled to a MDS tandem mass spectrometer with an atmospheric pressure ionisation (API) source. It is able to selectively analyse ions of interest and can detect and identify up to 32 separate substances simultaneously.

In the following experiments, the Scentinel was programmed to detect and identify a predetermined list of marker materials.

In a first experiment, vapours were collected from large closed wooden crates containing explosive placed in the crates with other items. The data was analysed using the MSA Scentinel tandem mass spectrometry. The presence of explosive in the crates was determined entirely by looking for marker vapours. The marker vapours used in this embodiment were: cyclohexanone (CH), 2-ethyl hexanol (2-EH), diphenylamine (DPA), dimethyl dinitrobutane (DMNB), 2,5- diphenyl-p-benzoquinone (BQ), ethylene glycol dinitrate (EGDN), nitroglycerin (NG), dinitrotoluene (DNT) and trinitrotoluene (TNT).

Three wooden crates were used in the experiment. Two of the crates were Im³ in volume. The third crate was smaller being 0.45 m³ in volume. All crates had wooden lids that could be placed on top of the crate but there was no way of fastening the lids in place and so some air gaps were present. The crates were situated in an outdoor barn and during the experiment the temperature ranged from 4-9C.

Each crate was closed and allowed to equilibrate at ambient temperature. After 1 hour, a stainless steel sorbent tube containing Tenax TA sorbent (Tenax tube) coupled to a pump, with a pump speed of 60 litres/minute, was placed under the lid of each crate and a vapour sample was collected. Air was sampled for three minutes from the two large crates and for one minute in the case of the small crate. The Tenax tubes were put on one side for analysis.

Samples of explosive were unwrapped and placed in each empty crate. Four pieces of explosive were used. The explosive types and estimated mass of each are listed below.

• Dynamite. 500g.

• Plastrite - 275g.

• Hexilene - 275g.

• Cast TNT - 20Og.

The Dynamite was placed in a Im³ volume crate named Ll. The Plastrite was placed in a Im³ volume crate named L2. The Hexilene and TNT were placed together inside the small crate with volume 0.45m³ named L3. The crates were left to equilibrate for 3 hours with the explosive inside. Vapour samples were collected by inserting a standard Tenax tube coupled to a small pump under the lid of each crate. Air was sampled for three minutes from the two large crates and for one minute in the case of the small crate. The Tenax tubes were put on one side for later analysis.

A variety of goods, representative of cargo, were then added to the crates. Ll was filled primarily with white goods. L2 and L3 were filled with machinery and various general items. The explosive was replaced in each of the three crates and the crates were allowed to equilibrate for three hours before another set of vapour samples was collected using the same sample collection process and equipment.

All samples were analysed using a desorber coupled to the Scentinel tandem mass spectrometer. The mass spectrometer was set up to automatically and only detect the presence of the markers cyclohexanone,(CH), 2-ethyl hexanol (2-EH), diphenylamine (DPA), dimethyl dinitrobutane (DMNB), 2,5-diphenyl-p-benzoquinone (BQ), ethylene glycol dinitrate (EGDN), nitroglycerin (NG), dinitrotoluene (DNT) and trinitrotoluene (TNT).

A comparison of the data from the empty crates, data from the crates containing explosive and data from the crates containing explosive and cargo materials was carried out.

Marker vapours, such as EGDN, 2-EH, cyclohexanone and DMNB, were found in the vapour samples from crates Ll and L3. These marker vapours were either not present at all in the empty crates or only present in low concentrations prior to the explosive being inserted into the crate. The use of tandem mass spectrometry to filter the ions during analysis meant that the presence of cargo in the crates made no difference to the detection of the markers. An increase in marker vapours was not detected in L2 and so the Plastrite was not detected in this experiment.

The Scentinel detector can be set to work in positive or negative ionisation mode. It was found that some markers were better detected in positive ionisation mode and some better in negative ionisation mode. In addition, some markers were better detected when a small amount of reactant to assist the reaction was added to the ionisation chamber. Therefore, in certain experiments, air from each box was drawn through three disks containing Tenax TA sorbent. Each of the three disks was separately analysed on the Scentinel, one disk in positive ionisation mode, one disk in negative ionisation mode and one disk in negative ionisation mode with reactant added.

Several double walled cardboard boxes (18x18x24 inches, volume 127.4 litres) were purchased and made up from new. One box was taped closed and covered in Clingfilm and left empty throughout the experiment as a control.

Each explosive type was placed in a different cardboard box. Each box was taped closed and covered in Clingfilm. The boxes were left to equilibrate. During this time the temperature remained approximately constant at 16C.

After equilibration, samples were collected by pushing a Tenax tube into the box and sucking air from the box through the sorbent using a pump operating at 40 litres/minute. Vapour collection time was for 10 or 20 seconds.

All explosive was detected easily in reasonable equilibration times and using very short sample collection times (10-2Os).

74g of crystalline TNT was placed in a box (18x18x24 inches) and left to equilibrate for 70 minutes at 16C before a vapour sample was collected. TNT, DNT and DMNB markers were all easily detected. 1Og PE4 was placed in a box (18x18x24 inches) and left to equilibrate for 15 minutes at 16C before a vapour sample was collected. DMNB and EGDN markers were easily detected.

18g C4 was placed in a box (18x18x24 inches) and left to equilibrate for 15 minutes at 16C before a vapour sample was collected. DMNB and EGDN markers were easily detected.

7Og Semtex A was placed in a box (18x18x24 inches) and left to equilibrate for 80 minutes at 16C before a vapour sample was collected. DMNB and EGDN markers were easily detected.

Vapour samples were collected from the empty box after many hours of equilibration. Marker vapours were either not detected, or only detected at low concentration.

In summary, all explosive was successfully detected using the marker explosive detection method shown and described herein which is presented in simplified flowchart form in Fig. 5.

It is appreciated that software components of the present invention including programs and data may, if desired, be implemented in ROM (read only memory) form including CD- ROMs, EPROMs and EEPROMs, or may be stored in any other suitable computer-readable medium such as but not limited to disks of various kinds, cards of various kinds and RAMs. Components described herein as software may, alternatively, be implemented wholly or partly in hardware, if desired, using conventional techniques.

Included in the scope of the present invention, inter alia, are electromagnetic signals carrying computer-readable instructions for performing any or all of the steps of any of the methods shown and described herein, in any suitable order; machine-readable instructions for performing any or all of the steps of any of the methods shown and described herein, in any suitable order; program storage devices readable by machine, tangibly embodying a program of instructions executable by the machine to perform any or all of the steps of any of the methods shown and described herein, in any suitable order; a computer program product comprising a computer useable medium having computer readable program code having embodied therein, and/or including computer readable program code for performing, any or all of the steps of any of the methods shown and described herein, in any suitable order; any technical effects brought about by any or all of the steps of any of the methods shown and described herein, when performed in any suitable order; any suitable apparatus or device or combination of such, programmed to perform, alone or in combination, any or all of the steps of any of the methods shown and described herein, in any suitable order; information storage devices or physical records, such as disks or hard drives, causing a computer or other device to be configured so as to carry out any or all of the steps of any of the methods shown and described herein, in any suitable order; a program pre-stored e.g. in memory or on an information network such as the Internet, before or after being downloaded, which embodies any or all of the steps of any of the methods shown and described herein, in any suitable order, and the method of uploading or downloading such, and a system including server/s and/or client/s for using such; and hardware which performs any or all of the steps of any of the methods shown and described herein, in any suitable order, either alone or in conjunction with software.

Features of the present invention which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, features of the invention, including method steps, which are described for brevity in the context of a single embodiment or in a certain order may be provided separately or in any suitable subcombination or in a different order, "e.g." is used herein in the sense of a specific example which is not intended to be limiting.

Claims

1. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in the vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if Cyclohexanone vapour is identified by said analyzing.

2. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if DPA vapour is identified by said analyzing.

3. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if EGDN vapour is identified by said analyzing.

4. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if DMNB vapour is identified by said analyzing.

5. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if NG vapour is identified by said analyzing.

6. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if DNT vapour is identified by said analyzing.

7. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if TNT vapour is identified by said analyzing.

8. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if Benzoquinone vapour is identified by said analyzing.

9. A method according to any of the preceding claims and wherein said identifying comprises identifying more than a pre-set threshold amount of said vapour.

10. A method according to claim 7 and wherein said alerting comprises alerting to presence of explosives, when at least one of the following set of vapours is identified by said analyzing: Cyclohexanone, Benzoquinone, 2-ethyl hexanol, Triacetin, DPA, EGDN, DMNB, NG, DNT, and TNT.

11. A method for detecting the presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, and alerting as to presence of explosives, if a predetermined group of marker vapours is identified by said analyzing.

12. A method for detecting the presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, and alerting to presence of explosives, if a predetermined group of marker vapours with predetermined relative intensities is identified by said analyzing.

13. A method for detecting presence of explosives in cargo, the method comprising: in a candidate identification stage, analyzing vapours present in a vicinity of each of a first plurality of explosive samples, thereby to identify at least one candidate explosive marker vapour; in a candidate evaluation stage, analyzing vapours present in a vicinity of each of a second plurality of non-explosive cargo samples and determining a frequency of occurrence of said at least one candidate explosive marker in said second plurality of non-explosive cargo samples; analyzing vapours present in a vicinity of the cargo, thereby to identify at least one marker vapour; and alerting to presence of explosives, if at least one marker vapour is identified by said analyzing, wherein said marker vapour comprises a candidate explosive marker vapour from among those identified in said candidate identification stage which was found, in said candidate evaluation stage, to have an acceptably low frequency of occurrence in non-explosive cargo samples.

14. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if Triacetin vapour is identified by said analyzing.

15. A method according to claim 13 wherein said second plurality of non-explosive cargo samples are culled from different environments characterized by different contaminants.

16. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour emitted from materials used to manufacture an explosive.

17. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour emitted by an additive added in the course of manufacture of an explosive.

18. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour previously absorbed, and subsequently exuded, by an explosive material.

19. A system for detecting presence of explosives in cargo, the system comprising: a vapour analyzer which is operative to analyze vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and a marker- vapour triggered explosives alarm operative to alert to presence of explosives, if at least one marker vapour is identified by said analyzing, wherein said marker vapour comprises a marker vapour, which tends to be present in cargo containing explosives and tends to be absent in cargo not containing explosives.

20. A system according to claim 19 wherein said vapour analyzer comprises: at least one vapour collection filter; and apparatus for sucking air out of cargo and through the vapour collection filter.

21. A system according to claim 19 wherein said vapour analyzer also comprises a spectrometer set up to automatically detect pre-selected vapour markers including all of: Cyclohexanone, Benzoquinone, 2-ethyl hexanol, Triacetin , DPA, EGDN, DMNB, NG, DNT, and TNT.

22. A system according to claim 19 wherein said marker vapour which tends to be present in cargo containing explosives and tends to be absent in cargo not containing explosives is not itself a vapour of an explosive.

23. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour emitted by an additive to an explosive material.

24. A system according to claim 19 wherein said vapour analyzer also comprises a spectrometer set up to automatically detect pre-selected vapour markers including at least one of: Cyclohexanone, Benzoquinone, 2-ethyl hexanol, Triacetin , DPA, EGDN, DMNB, NG, DNT, and TNT.

25. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one vapour; and alerting to presence of explosives, if 2-ethyl hexanol vapour is identified by said analyzing.

26. A method for detecting presence of explosives in cargo, the method comprising: analyzing vapours present in a vicinity of the cargo, thereby to identify at least one marker vapour; and alerting to presence of explosives, if a marker vapour is identified by said analyzing.

27. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour emitted by at least a component of an explosive material.

28. A method according to claim 27 wherein said candidate explosive marker vapour comprises a vapour emitted by a chemical used to manufacture at least one component of an explosive component.

29. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour emitted by a contaminant of an explosive material.

30. A system according to claim 19 wherein said marker- vapour triggered explosives alarm is operative to alert to presence of explosives, if at least one marker vapour is identified by said analyzer, wherein said marker vapour comprises a vapour from an explosive that is a contaminant vapour in the explosive that is found in the cargo.

31. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour previously exuded by an explosive material which is present in an environment surrounding a second explosive material, is subsequently absorbed by said second explosive material, and is then re-emitted.

32. A method according to claim 27 wherein said candidate explosive marker vapour comprises a vapour emitted by an additive material mixed with said component during manufacture.

33. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour emitted by an explosive component.

34. A method according to any of claims 1 - 8, 10, 14 and 25 wherein said analyzing comprises: collecting samples from the cargo; transporting the samples to an analyzer disposed at a distance from the cargo; and using said analyzer to analyze said samples.

35. A method according to claim 34 wherein said collecting comprises sucking air containing vapours out of the cargo and through vapour collection filters, at each of a plurality of cargo sampling positions.

36. A method according to claim 27 wherein said candidate explosive marker vapour comprises a vapour emitted by an explosive component.

37. A method according to claim 13 wherein said candidate explosive marker vapour comprises a vapour previously exuded by a non-explosive material which is present in an environment surrounding an explosive where this vapour is subsequently absorbed by the explosive and re-emitted.

38. A method according to claim 35 wherein at each of the plurality of cargo sampling positions, air containing vapours is sucked through at least a pair of vapour collection filters, and wherein said analyzing comprises analyzing one filter in each pair in positive ionization mode and another filter in each pair in negative ionization mode.