CA2190070A1

CA2190070A1 - Apparatus for and method of scanning objects for the presence of trace chemicals

Info

Publication number: CA2190070A1
Application number: CA002190070A
Authority: CA
Inventors: Ludmila Danylewych-May; Frank J. Kuja; John Henry Davies
Original assignee: Barringer Research Ltd
Current assignee: Smiths Detection Toronto Ltd
Priority date: 1996-11-12
Filing date: 1996-11-12
Publication date: 1998-05-12

Abstract

A method of and apparatus for collecting a sample from an object, for analysis in an analyzer, provides a substrate which is inert so as not to interfere with any sample and not to suppress any sample. The substrate is mounted in a fixed retaining means, to hold the substrate stationary and to present the substrate for contact with an object; for example the substrate can be mounted facing upwards. Then, an object is presented to the substrate and one side of the object of the object is rubbed against the substrate, to transfer a sample of trace particles and liquids onto the substrate.The trace particles and liquids are then desorbed into the inlet of an analyzer for analysis. The invention provides a simple technique for collecting a sample from travel documents and the like, to check to see if an individual has been handling, for example, drugs or explosives.

Description

-Title: Apparatus for and Method of Sr~nnin~ Objects for the Presence of Trace Chemicals FIELD OF THE INVENTION
This invention relates to the collection from the surfaces of objects, for example, documents and other like sheet-form objects, samples of trace particles or liquids, or other compounds for chemical detection by various analytical means, such as an ion mobility spectrometry (IMS), gas chromatography (GC), liquid chromatography (LC), mass spectrometry (MS) and other methods, the compounds being present on the surfaces of various documents, either as traces within particles or as discrete particles or aerosols, droplets within finger oils, or the like. The invention more particularly relates to a reliable explosives screening capability for checking passengers before they board various modes of transport. However, the invention also encompasses means to rapidly screen documents for traces of other chemicals of concern, such as but not limited to: narcotics, illicit drugs and tracers.

BACKGROUND OF THE INVENTION
Presently passengers on high risk transportation, such as aircraft, are screened for concealed weapons. This is carried out on passengers using a Walk-Through Metal Detector (WTMD), which' can be followed by a manual inspection using a hand-held metal detection or magnetometric wand. In parallel, the passenger's luggage and other items are passed through an X-ray machine for visual inspection. Because of the danger from X-radiation dosage, it is not practical to X-ray people. Some attempts have been made using very low dosage X-ray devices, but they have failed to gain acceptance in large part due to public objection to whole body X-ray scanning. The WTMD technique specifically looks for metal such as is found in knives and handguns, because it is an inductive electromagnetic technique. Explosives themselves do not register on WTMDs even when the system gain is set very high. The value of WTMDs is in the indirect detection of any metallic objects that may be associated with a bomb, such as metal encased batteries or metallic fusing devices or _ 21 9~07û

metal wiring, which can be to varying degrees difficult to impossible to detect.
Many concepts have been developed for screening passengers, their luggage and other travel items. U.S. Patent 4,909,090 teaches hand-operated vapour samplers to thermally desorb explosives vapours from a sampling surface, which vapours are subsequently trapped on collector surfaces. Because modern plastic explosives have such low vapour pressures this approach is very unsatisfactory. Drugs also have very low vapour pressures and are equally undetectable by vapour sampling.
Consequently, because of these difficulties with vapour sampling, trace particle collection affords an alternative approach, quite independent of vapour pressures. Trace particle collection applications is described in early patents of Barringer Research Ltd., the assignee of the present invention, namely U.S. Patents 3,970,428, and, 4,220,414, 5,425,263, and 4,192,176. These proposals include: surface physical particle collection with pan-brush arrangements; vacuum suction onto various substrates; and the use of swabs, swipes, gloves and finger mitts. By way of example, U.S. Patent 5,476,794 describes particle removal with a glove.
Gloves, mitts and swipes require the intermediate step of transfer of the particles/trace chemicals from the glove to the analytical device. Also, direct contact of the sampling media with the operator's hand is required unless protective gloves are used. But, even protective gloves can get contaminated and may need frequent changing. Suction devices to vacuum the glove or mitt, see U.S. Patent 5,476,794, have been proposed. It has been shown that loss of sample is a severe problem with this approach because of the incomplete transfer from the glove. Suction devices have to be cleaned thoroughly after any positive hit and the suction causes glove/cloth/lint fibres to be released which obstruct the collecting substrate and present interfering chemicals or fluff/lint.
Collection or filter discs can be inserted directly behind sampling heads to prevent the particles entering suction lines which could then later dislodge to give false alarms. The filter discs are then presented to a thermal desorption device which volatilizes the collected material for chemical analysis. The disadvantage of this technique is that it requires the presence of relatively loose particles of analytes of interest or dust particlescontaminated with analytes. The vacuum method is also impractical for directly sampling people.
Another approach described in the prior art is the use of air curtains. A passenger enters a portal and air jets sweep away any explosives vapours for subsequent analysis. Sampling rates have varied from 10 L/s to 1,000 L/s and sample air volumes have varied from 100 L to 1,000 L, dependent upon the type of analyzer used and its limit of detection to the analytes sought. Detector volumes are usually very small, typically less than 1 mL, so that the air sample volume must be reduced by very large factors. This causes significant losses in sensitivity (Jenkins et al.). In addition, the inefficiencies of vapour sampling as described above make this method highly ineffective.
Alternatively, low volume air sampling obtained directly from passengers' bodies has been described. Low volatility explosives unfortunately can adsorb onto the inner walls of sampling lines which of necessity have very small bores to keep analyzer response times short. The trapping of the explosives vapours for desorbing into carrier gas streams has been used to reduce air sample volumes. The use of infra-red (IR) heat sources has been previously described but cannot be used directly on people because surface temperatures up to 100~C or greater are necessary to release explosive vapours (Bromberg et al., 1992).
Portals to collect explosives vapour have proven to be unworkable. The walk-through portals using air curtains or jets have proven unable to dislodge explosive particles from the clothing of individuals undergoing inspection since they are electrostatically held firmly to the clothing. Additionally, an explosive device can be hidden inside clothing rendering detection even more difficult.
Another approach and the subject of a recently filed patent application by the same inventors, is the use of tokens or tickets which are dispensed from a dispenser. The person removes the token by pulling it free between his/her finger and thumb. The pressure transfers possible explosives or drug traces to the token which is then analyzed. A
disadvantage is that individuals could have very clean hands, whereas their 5 travel papers are likely well handled even many days before and during travel.
Yet another approach is disclosed in U.S. Patent Application 08/627,196 to two of the inventors of the present application. That earlier application discloses a hand held sampling apparatus that is suitable for 10 running over surfaces of relatively large objects such as suitcases. It is not fixed and requires manual operation by a trained operator, and subsequent handling of the substrate to place it in the inlet of an analysis device. It does not provide a quick and simple technique, suitable for obtaining a sample from travel documents and the like.
It can be appreciated that the above remarks for explosives detection equally apply to drug detection, and there is a common reciprocity in application. Narcotics and modern plastic explosives are very difficult to detect with X-ray technologies, even when advanced multi-energy systems are used. Thus, complementary detection methodologies are needed that 20 supplement existing traditional techniques.
Explosives residues on skin are hard to remove, and persons handling explosives are easily and inadvertently contaminated. This contamination is passed on to their travel documents, such as tickets, boarding passes and passports. Therefore, the indirect screening of 25 passenger's documents could provide important information on possible explosives concealed on that person or in his/her belongings. It is obvious that similar trace contamination can be passed to documents from the handling of narcotics, drugs, substances of abuse and other contraband materials. Document scanning indirectly screens the hands without 30 subjecting people to direct sample collection procedures so it is very passenger friendly. This concept allows all passengers to be rapidly screened without undue disruption to the passenger traffic flow, and could easily be 21 90C~7~
.

integrated into existing passenger checkpoints.
Passenger prescreening using a document scanner involves swiping boarding passes or other documents such as passports against an appropriate surface, followed by analysis.
Substrate material for document scanning must be free of interference, and must withstand many repeated document wiping and heating cycles without physical and chemical degradation. The substrate must efficiently remove explosives or drug traces or particles containing explosives or drugs from documents.
For a document scanner device, the explosives or drug traces of concern are those present on a person's hands. The presence of explosives or drugs on a person's hands may be due to either primary contamination from handling explosives or drugs directly or from secondary contamination where the person under test came into contact with an explosives or drug contaminated surface. Analytic devices can be affected by suppression effects from various contaminants present with the explosives or drugs which accumulate on hands, primarily naturally excreted oils and cosmetic products like creams, hand softener agents, perfumes and aftershave lotions. The effect of finger oil background on various analyzers is therefore an important consideration.

SUMMARY OF INVENTION
In accordance with a first aspect of the present invention, there is provided a method of collecting a sample from an object, for analysis in an analyzer, the method comprising the steps of:
(1) providing a substrate which is inert so as not to interfere with any sample and not to suppress any sample;
(2) mounting the substrate in a fixed retaining means, to hold the substrate stationary and to present the substrate for contact with an object;

(3) presenting an object to the substrate and rubbing one side of the object against the substrate, to transfer a sample of trace particles and liquids onto the substrate; and (4) desorbing the trace particles and liquids into the inlet of an analyzer for analysis.
Preferably, the substrate is generally planar, and step (3) 5 includes displacing a central portion of the substrate out of the plane of thesubstrate for contact with the object, whereby any sample of particles and liquids is transferred to the central portion of the substrate. More preferably,the substrate is mounted in a holder facing upwards and a central portion of the substrate is raised by means of a boss displaced relative to the holder.
Advantageously, the method is carried out using a substrate which shows no interference and no suppression to analytes of interest, is efficient at removal of a sample from an object, is not contaminated by contaminants commonly found in ambient air, readily desorbs a sample, and enables a sample to be desorbed by heating and vaporization, without 15 degradation of the substrate. The substrate can comprise at least one of glass fibre, teflon, paper, cotton, linen, wool and silk, and further the substrate ispreferably porous or semiporous. The substrate may be chemically treated to enhance the ability thereof to trap and transfer an analyte of interest.
Step (3) is conveniently carried out at a first location, and the 20 substrate is then transferred to a second location adjacent the inlet of an analyzer, to carry out step (4). Following step (4), the substrate can be moved to a third location where it is permitted to cool, prior to returning to the first location to receive a further sample. Advantageously, this is carried out by a mechanical handling means which transfers the substrate between the 25 first and second locations, and third location if present, whereby manual handling of the substrate is not required. The handling means can comprise a circular plate mounted for rotation about a central axis and including at least three substrates, wherein the three locations are provided around the plate and substrates are moved between the locations by rotation of the 30 plate. A fourth location can be provided into which each substrate is moved by the circular plate and at which fourth location each substrate is subject to an elevated temperature, to clean the substrate, the fourth location being 2 i J u 7 ~
-provided between the second or third locations.
The method can be carried out to detect the presence of an analyte comprising one of drugs and explosives, and in one aspect of the present invention is carried out using a sheet-from object, preferably a travel document selected from tickets, boarding passes, passports and identification documents. It can also be used to detect a chosen target compound that has been applied to a target object of interest. Then if one tests a documents, or other object associated with a person, and this shows the presence of this target compound, this indicates that the person has been in contact with the target object.
In accordance with another aspect of the present invention, there is provided an apparatus for collecting from the surface of an object trace particles and liquid as an analyte for analysis, the apparatus comprlsmg:
a transfer substrate which is generally planar;
a retaining means for holding the substrate stationary; and a displacement means for displacing a central portion of the substrate out of the plane thereof, to enable a side of the object to be rubbed against the central portion of the substrate.
Preferably, the displacement means comprises a boss and a mechanism for displacing the boss generally perpendicularly relative to the substrate. The boss more preferably presents a generally spherical surface for contacting and displacing the substrate. The mechanism can comprise one of a handle and an actuation system.
The apparatus preferably includes a mechanical handling means, for moving the substrate between different locations, and this can comprise an arm mounted for rotation about an axis and including a free-end portion on which the substrate is mounted, which free-end portion is moveable between different locations, and an actuating handle attached to 30 the arm for displacing the arm between the different locations. It may alternatively comprise a circular plate mounted for rotation.
A further feature of document scanning is that it allows police, security services and customs officers the opportunity to screen a wide variety of travel document and personal papers, such as visas, driving licences, identification cards, etc. It is obvious that such investigation techniques can be used by security and intelligence services in forensic 5 evidence gathering and tracing contacts with either drugs or explosives, or other sought chemicals. Also, it can be appreciated that for certain clandestine operations, such as undercover police work in establishing who may be handling sensitive documents or illegally removing or copying classified documents, such controlled documents can be pretreated with 10 traces of special marker chemicals which will transfer to the hands of anyone handling such treated documents. Thus document scanning can be applied in a wide range of circumstances, not only aviation security, but for all forms of travel, border crossing, customs inspections, facility protection, police and intelligence forensics work and other similar applications.
While the invention relates to its primary use as a document scanner for the detection of traces of drugs and explosives, it can be recognized that it can be used for mass non-invasive conditions screening.
Several medical and clinical and dietary deficiencies are evidenced in the skin, its subcutaneous materials and finger oils. Special cards could be 20 provided to mass-screen individuals for the presence of absence of particular chemicals. A further application might be in the screening of military personnel after suspected chemical or biological attack. The soldiers (or civilians) could be rapidly screened for the presence of Chemical Warfare (CW) or Biological Warfare (BW) materials, which may be present, 25 through the action of the soldiers contacting a card via their fingers (protective gloved or not) .
A further application is the monitoring of CW/BW attack through the use of exposure cards which could be left unprotected to the atmosphere. It is well known that CW/BW agents are generally dispersed 30 as aerosols and that threat levels are determined by the quantity (mL) of agent received per square metre of exposed surface. Thus, special cards, which could be selectively pretreated could be placed around position to be -protected. The cards would be swiped on the document reader from time-to-time to assess the presence or absence of the agents/analytes sought.

BRIEF DESCRIPTION OF DRAWINGS
For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference can now be made, by way of example, to the accompanying drawings in which:
Figure 1 is a perspective view of a first embodiment of a document scanning device in accordance with the present invention;
Figure 2a is a plan view of a second embodiment of a document scanning device in accordance with the present invention;
Figure 2b is a side view of the document scanning device of Figure 2a;
Figure 3 is a schematic view showing an inlet of an IMS
analyzer and insertion of a transfer substrate for analysis;
Figure 4 is a schematic view of a third embodiment of a document scanning device in accordance with the present invention; and Figure 5 is a schematic view of a fourth embodiment of a document scanning device in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to Figure 1, a first embodiment of the apparatus of the present invention is generally noted by the reference 10. The apparatus 10 has a transfer substrate 16 that is slotted into a mechanical holder 14. The transfer substrate 16 is held in the mechanical holder 14 by edge rails 32 or other like arrangements. The mechanical holder 14 is transferred from the apparatus 10 to an analyzer of choice via support rails 28. Below the substrate is a boss assembly 22 which includes a boss 18. The boss assembly 22 is connected via a suitable mechanical interconnection 26 to a handle 24 with which assembly 22 can be moved vertically between two positions. In the rest or lower position, the boss assembly 22 does not touch substrate 18 and allows free movement of holder 14.

-In use, the handle 24 is moved to raise the boss 18 via a suitable mechanical linuage. The boss 18 makes contact with the transfer substrate 16 and deflects the centre of it upwards and beyond the surface plane of the mechanical holder 14, i.e. the substrate becomes dished with its 5 edges still retained in the holder 14. A document of interest 12 with trace chemicals of interest 30 is then rubbed against the transfer substrate 16.
Since the transfer substrate 16 extends above the surface plane of the mechanical holder 14 there is no contamination of the mechanical holder 14 during the rubbing process. Upon completion of the rubbing process, the 10 transfer substrate 16 is returned to the surface plane of the mechanical holder 14 by reversing the movement of the handle 24. Once the transfer substrate 16 has been returned to the surface plane of the mechanical holder 14, the mechanical holder 14 is transferred via the support rails 28 into the desorption stage of an IMS analyzer 70 as shown in Figure 3. It will be 15 appreciated that the IMS analyzer 70 is shown purely by way of example, and that the invention is applicable to a wide variety of analyzers, as noted above. IMS analyzers are well known in the art, and are described, for example, in U.S. Patents such as 5,405,781 and 5,071,771.
The transfer substrate 16 is pressed between sealing rings 81 20 and 82 and against an inlet 83 of the analyzer 70. An anvil assembly 84 with a heater 85 is driven by a servo-actuator 87, which presses the anvil assembly 86 against the inlet 83 to seal the substrate 16 between the sealing rings 81, 82. An inert sample gas or airflow 86 is then provided to carry the desorbed vapours into the analyzer 70.
After complete desorption, the substrate 16 is allowed to cool before being reused. If a substrate becomes worn or still shows traces of contaminants even after desorption, then it is replaced.
It is to be appreciated that the apparatus for Figure 1 can incorporate a number of variants. Thus, either one or both of the boss 18 30 and the holder 14 can be mounted for movement. The boss 18 and holder 14 can be mounted so as to establish two or more different positions for the substrate 16. This movement can either be horizontal or vertical, and can 21 ~007G

include motion in a circular arc. The arrangement could be such as to provide at least three different positions, namely: as shown in Figure 1, a sample collection position; a desorption position, as shown in Figure 3; and a cooling position, where the substrate 16 is cooled prior to returning to the 5 Figure 1 position.
Reference will now be made to Figures 2a and 2b, which shows a second, preferred embodiment of the apparatus in accordance with the present invention. Here, the apparatus is shown mounted to the side of an IMS analyzer. Here, the second embodiment is indicated generally by the 10 reference 40, and is shown mounted to a frame 42 of an IMS analyzer. As detailed below, mounted within the frame 42 is an actuation switch 44 having a switch arm 46 located immediately behind an aperture 48.
The apparatus 40 includes a bracket 50. The bracket 50 includes an elongate element which is formed from sheet metal or the like and 15 which is bent to provide numerous parts in various vertical planes. This includes a central part 52 defining a slot 54. At a free end, the bracket 50 includes a U-shaped portion 56. A boss 58 with an associated drive piston 60 is mounted to this U-shaped part 56 for vertical movement of the boss, as detailed below. At its inner end, the bracket 50 provides a vertical shaft 62.
20 A handle 64 and arm 66, shown in two positions as 66a and 66b, are secured together and mounted on the vertical shaft 62, which is rotatable with respect to at least one of the bracket 50 and the handle and arm 64, 66.
The arm 66 includes a straight central portion 68, in which is mounted an actuation pin 70. The pin 70 is spring loaded, and so as to 25 actuate the switch 44, as detailed below.
At its free end, the arm 66 includes a circular support ring 80 which provides a mechanical holder 82 for a substrate 84.
Figures 2a and 2b also show, at 86, the anvil assembly of the IMS analyzer, with the actual inlet of the IMS analyzer being omitted from 30 Figure 2. Figure 2 shows the arm 66 in the desorption position, indicated at 66a, in which substrate 84 is located immediately above anvil assembly 86.
In ghost or dotted outline, there is shown a sample collecting position, with 2 1 90û70 the arm indicated at 66b and the handle at 64b.
In use, to permit movement to and from the desorption position, the boss 58 is lowered. The arm 66, by means of the handle 64 is swung to the sample collection position 66b. As for the first embodiment, 5 the boss 58 is raised by action of the drive piston 60, displacing the centre of the substrate 84 above the plane defined by support ring 80, and a sample ticket or other document is rubbed across the top of the substrate, projecting above the U-shaped portion 56. It will be appreciated that the slot 54 is to accommodate the head of the actuation pin 70 and enable the arm 66 to 10 reach position 66b.
With a sample collected, the boss 58 is lowered by the piston 60 and the handle 64 is used to swing the arm 66 into the desorption location 66a. As it reaches this location, the actuation pin 70 passes through the aperture 48 and displaces the switch arm 46 to actuate the switch 44. Any 15 extra motion is taken up by the spring biassing of the pin 70. The actuation switch 44 enables the anvil assembly 86 to be raised, either automatically upon actuation of switch 44, or by other operator interaction (not shown).
As for the first embodiment, the anvil assembly 86 presses the substrate 84, between sealing rings, against the inlet in the IMS analyzer (not shown), as 20 detailed in Figure 3 described above. Heating and desorption take place as mentioned above, with any desorbed trace substances of interest being entrained in a gas flow, for analysis.
After desorption, the anvil assembly 86 is lowered, the heater turned off, and the arm 66 swung back to the location 66b. The substrate 84 25 is then ready to collect a further sample.
Figure 4 shows an alternative embodiment generally noted by the reference 100 and intended for moving a substrate, here again indicated at 16, between different stations. This embodiment, and also that of Figure 5, can be used, in conjunction with the apparatus of Figures 1 and 2. The 30 apparatus 100 has a plurality of stations positioned in a circular plate 105 which can be rotated in stepped increments about its axis 107. In this embodiment a three stage plate containing three identical transfer substrates 21 ~0070 16 at positions 109, 110 and 111 is depicted. In use, the transfer substrate 16 at position 109 collects analytes transferred from a document while the previous transfer substrate 16 at position 110 is undergoing analysis within the analyzer 112. Following the thermal desorption, a resting stage is 5 introduced at position 111 to allow cool down so as not to prematurely vaporize materials from too hot a transfer substrate 16 when the next document sampling occurs.
Figure 5 shows an alternative embodiment generally noted by the reference 120. This embodiment is similar to Figure 4, but includes a 10 four stage plate containing four identical transfer substrates 16 at positions 127, 129, 131 and 133. The four positions are: position 127 for forced cooling before readiness for the next document; position 129 for sample collection;
position 131 for desorption and analysis; and position 133 for heating to ensure bakeout of all traces. It can be readily appreciated that the analyzer 15 125 may contain the desorption stage and the heating or baking stage internally or externally, as a matter of design convenience sequence.
While preferred embodiments have been described, it will be appreciated that numerous variations and modifications are possible within the scope of the present invention. Particularly there are several ways in 20 which the substrate can be elevated to accomplish the sampling.
It can be appreciated by those well versed in the art that the movements of the mounting arms and boss/pistons can be performed by electric drives and solenoid actuators, that limit switches can be added to initiate start and stop actions to avoid damage to the mechanical 25 arrangement, and photocells can be incorporated to initiate start-up of the desorption and analysis.
While earlier reference has been made to the rotation of the sampling device through 90~, it can be appreciated that a plurality of positions are possible, as for example, a second position of 90~ rotation in 30 counter direction such that two desorbing positions are possible, as for example, one for drugs analysis and the other for explosives analysis, or for desorbing at two different temperatures or by the addition of a reactant gas 2 1 ~0070 -or other additive chemistry at one station as compared to the other.
It can be further appreciated that at the desorption-measurement stage, controlling electronics can be employed to sequence the various events, namely: the sampling, movement of sampling assembly 5 into the desorbing position, raising of the anvil, initiation of sample air/gas flows and activation of the heater, and the enabling of all other necessary measurement and housekeeping functions of an analyzers, such as powering, data collection, signal averaging, vacuum pumping, chromatographic column switching, backflushing, purging, introduction of reactant gases, calibration gases or other like requirements.
It will also be appreciated to those well versed in the art that the selection of substrate materials is dependent on the type of analyzer selected for the trace measurements.
Although Figure 3 describes the process of desorbing into an IMS analyzer, a preferred analyzer, the concept is by no means limited to this type of device Other analyzers such as mass spectrometers, chromatographic detectors or chemiluminescent devices can equally well be used, since they are proven high sensitivity detectors of drugs and explosives at the trace levels likely to be encountered.
The essential features of the invention is the apparatus and method whereby documents and other objects of interest can be easily scanned to remove any trace chemical components for rapid analysis.
While sheet-form documents, such as travel documents, are often readily available, the invention could be applied to any object that is readily handled, e.g. a cigarette lighter, handbag, portable radio/CD player. A
suitable substrate is needed upon which the objects of interest are to be swiped or rubbed thereby ensuring an efficient transfer of trace amounts sufficient for successful analysis. Research indicates that the amounts likely to be present on contaminated documents are in the range 10 to 100 ng and greater. Allowing for less than 50% transfer to the substrate, analytical devices with limits of detection of 500 pg to 1 ng are required. Suitable devices are chromatographic analyzers, mass spectrometers, 21 soo7n chemiluminescent detectors and ion mobility spectrometers (see Douse, 1987; Rounbehler et al, 1982). For the purpose of description and by way of example, the following description uses ion mobility spectrometry (IMS) as the analytical technique. It will be apparent to those skilled in the art that 5 other analyzers can equally be used for the purpose, without in any way detracting from the novelty of the invention. It will also be apparent to those skilled in the art that some analytical techniques will be more efficient or preferred than others by virtue of various operational factors, such as size of equipment, field mobility, need for inert carrier gases, susceptibility to 10 interferences from various types of inks or paper treatment chemicals or commonly used toiletry products on hands, such as hand creams and lotions, softeners and the like. Practical considerations of the above factors favour the use of IMS, but the invention is in no way limited to this particular analyzer.
A further consideration is that while the analysis can look for substances, e.g. drugs or explosives, that may be being illicitly carried, it could also be used to detect certain target substances. Thus an object or objects of interest, could be treated with a unique target substance, which is readily detected by the chosen detector. The analysis of documents or other 20 objects handled by a person will give an indication whether that person has handled the target object of interest.
Essentially therefore the substrate material and means whereby its surface contact to the document under inspection is accomplished are key to the method. Various substrate materials and means to engineer good 25 contacts with documents for efficient trace transfer and means to provide repetitive use without contaminating the mechanical structure holding the substrate have been the focus of various research studies by the present inventors. Different piston or boss base surfaces that contact and raise a portion of the collection substrate onto which the document is swiped have 30 also been investigated. Two different boss materials investigated were soft textured plastic resembling a domestic scouring pad for cleansing kitchen utensils and a smooth hard surface plastic.

21 qO070 Explosives contaminated fingerprints on landing cards and boarding passes were generated and results are summarized in Table 1. The amount of explosive transferred from the landing card was evaluated as follows. After discarding the first 30 fingerprints, a group of 8 sets 5 containing 3 sequential fingerprints were generated on landing cards. The first set of cards with fingerprints was wiped on a Teflon substrate with a hard piston base, the second set with a soft piston base and the third set was extracted with acetone. Although this extraction method does not provide an absolute value for the amount of explosive present in the fingerprints, it 10 provides information on relative concentrations in fingerprints from set to set, which is sufficient when only a comparative performance of piston base materials is investigated.
The comparative transfer efficiency using the hard and the soft bases for the piston was found to be explosive dependent; however, for all 15 three explosives tested, TNT, PETN from detonating cord and RDX from C-4, the hard surface always provided better results.

21 ~0070 , Table 1: Comparison Between Two Document Scanner Piston Type TNT C4 Detonating (RDX) Cord (PETN) Amount Deposited on Cardl (ng) 160 +92 20 +2 30 +4 DocumentScannerBase Type Hard4 Soft5 Hard Soft Hard Soft Cumulative Amplitudes 2(du) 8242 4783 5361 3861 8621 5230 +1643 +1350 +952 +1515 +3104 +2270 Equivalent Amount of Explosive Detected (ng) 25 5 2 1 10 8 Transfer Efficiency3 16% 3% 10% 5% 33% 27%

Approximately one square inch of the card surrounding the explosive fingerprint was extracted with 500',11 acetone for 2 minutes. A 2~1 aliquot of the extract was analyzed in the IONSCAN (an IMS analyzer made by the assignee of the present invention) using a Teflon filter. Calibration curves forTNT, RDX and PETN were established by depositing known amounts of explosives from solutions onto the card and extracting in the same manner.
2 Signals are expressed as the sum of cumulative amplitudes of all peaks formed.
3 Transfer Efficiency = Equivalent Amount of Explosive Detected x 100%
Amount Deposited on Card 4 Hard smooth surface Compressible abrasive surface The above test was carried out with landing cards. Once methods and optimum conditions were established, a comparative study with boarding passes from various airlines (5 in total) was conducted.
The initial tests of Table 1 on particle transfer mechanism and transfer efficiency were carried out using a "fingerprint" method. Such a fingerprint method produced consistent results within one series of prints, and therefore provided reliable data. However, variability from one series to another was sometimes an order of magnitude with the same person and likewise when different persons were used.
To study the transfer efficiency and the minimum amount 21 90a70 required for detection, reproducibly known amounts of explosives had to be deposited. This was accomplished by preparing solid particle solutions for TNT, NG and ammonium nitrate. For the transfer efficiency of RDX (C-4), an emulsion in water was used. A known amount of particle mixture 5 (lmg) was analyzed using an IMS to determine the explosive concentration in these mixtures. The transfer efficiencies of particles travelling through the following routes were investigated and the results are summarized in Table 2, namely from contaminated documents to document scanner substrate, and overall transfer from contaminated fingers to scanner 10 substrate via documents.
The transfer efficiency from the contaminated documents to the substrate or filter has been determined using lmg of explosive particles deposited on a landing card with the particles spread evenly across an area of approximately one square inch. The contaminated surface was wiped on 15 the document scanner twice and analyzed. The particle transfer efficiency from the document to the Teflon substrate was determined by comparing the resulting signals to signals obtained by desorbing the same amount of explosives directly deposited on a Teflon filter. The overall efficiency from contaminated fingers to the substrate via document contamination was 20 determined by comparing the equivalent amount of explosive detected from the substrate to the amount of explosive applied to the fingers. The equivalent amounts of explosives transferred and detected from contaminated landing cards were obtained from calibration curves.
Calibration curves have been established by plotting the detector 25 signal vs the amount of explosives analyzed from a clear Teflon filter.
Equivalent amounts of explosives were then determined by looking up the detector signal amplitude found in an experiment and correlating it to the amount of explosives using the calibration curve. Efficiencies were calculated using the ratio of the equivalent amount to the actual amount of 30 explosives, expressed in percent.

- 2 1 ~0070 Table 2: Sllmmary of Particle Transfer Efficiencies Explosive From Fingers to From Document to Document to Teflon Teflon Amount Amount Deposited n Fs2 (%) Deposited n DS3 (%) on Finger on Finger g 0.10 lOOng 46 NG l!lg 0.03 lOOng 28 Ammonium l~lg 0.10 lOOng 21 Nitrate RDX 1.14~1g 0.30 38ng 29 Reported results are based on averages of 6 to 10 samples and the variations were within 20 to 30% of the average values except for n Fr ~f NG where it varied up to 65%.
2 n FS = Equivalent Amount of Explosive Detected by Document Scanner x 100%
Amount of Explosive Applied to Finger 3 n DS = Signal from Explosive Transferred to Teflon Substrate from Document x 100%
Signal from Explosive Directly Deposited on Teflon Substrate The transfer efficiency DS from the document to the Teflon substrate, when spiked directly, is between 20% (ammonium nitrate) and 50% (TNT). For all explosives, the transfer efficiency FS is considerably 15 lower, substantially less than 1%. The additional losses must be associated with the poor transfer from fingers to the document as well with imbedding particles into the surface of the document, resulting in poorer pickup by the document scanner. Similar experimentation has been undertaken for several common narcotic substances of abuse such as cocaine, heroin, 20 amphetamines and like narcotics, with similar results.
Table 3 details results from experiments (carried out as described above) to determine suppression effects of common cosmetic products on the signal strength of explosives. It was also found that blank (new) boarding passes suppress explosives signals to some extent, due to the 25 presence of chemicals from the manufacturing and printing process. Used (clean) boarding passes from various airlines were also investigated to determine possible suppression effects, and those results are also included in Table 3.

2 1 ~0370 ~ .~

Table 3: Percent Suppressionl Due to Common Cont~minants on Document Scanner TNT RDX PETN NG AN
Arnount Analyzed (n~) 1 0 2 1 0 1 0 5 Suppression due to blank boarding 13 - 54 % 0 % 0 % 0 - 9 % 26 - 47 %
passes (new) Hand Lotions Vaseline 65 % 0 0 40 % 45 %
Shiseido 74 % 0 0 38 % 89 %
RirnCorp 52 % 0 0 41 % 66 %
Perfumes Obsession 0 % O 0 70 % O
Drakkar Noir 26 % 0 0 20 % 0 JilSander 28 % 0 0 16 % 0 Aftershaves Polo 65 % 8 % 18 % 23 % 59 %
Drakkar Noir 71 % 12 % 7 % 48 % 66 %
Azzaro 79 % 10 % 13 % 50 % 54 %
Used Boarding Canadian Air 51 % 21 % 8 % 5 % 0 %
Passes Cathay Pacific 55 % 15 % 32 % 21 % 0 %
Northwest 64 % 0 % 23 % 18 % 11 %
KLM 49 % 5 % 4 % 8 % 14 %
% Suppression = (1 - Signal obtained in presence of fingerprint ) x 100%
Signal obtained from clean filter 2 Average values of at least 8 samples are reported.
The suppression effects are expressed in percent, calculated from the ratio of the signal of an amount of explosives from a transfer experiment and the signal of an identical amount of explosives, resulting from analysis from a clear Teflon filter. The expressed suppression effects include any 15 suppression due to the boarding pass itself.
The variability in the suppression effect from new boarding passes is most likely associated with the amount of the contaminants (ie. ink, fibre, etc) transferred onto the filter. The degree of transfer is very much dependent on the pressure applied during the document swiping which is 20 carried out by hand. The suppression effects on TNT, NG and ammonium nitrate due to the presence of cosmetic products, as reported in Table 3, include the suppression due to the blank boarding pass. The observed suppressions on RDX and PETN were due to cosmetic products alone since there was no suppression from the new boarding pass.

The general contamination found on hands and transferred to documents represent a combination of natural oils, hand lotion, perfumes, aftershave, etc. All explosives tested were detected at their nanogram range in the presence of contaminants, which is a reasonable level of explosives~ expected to be found in practical deployment.
The various explosives that can be used are as follows:
TNT Trinitrotoluene NG Nitroglycerine DNT Dinitrotoluene PETN Pentaerythritol RDX Cyclo- 1,3,5-trimethylene-2,4,6-trinitramine RDX Cyclo- 1,3,5,7-tetramethylene-2,4,6,8-tetranitramine Tetryl Trinitro-2,4,6 phenylmethylnitramine Examples of substances that can be used a taggants, i.e. as substances 15 to identify an object and anyone who has handled the object, are:
EGDN Ethylene Glycol Dinitrate (also in Dynamite) DMDNB 2,3 Dimethyl-2,3-dinitrobutane MNT Mononitrotoluene

Claims

1. A method of collecting a sample from an object, for analysis in an analyzer, the method comprising the steps of:
(1) providing a substrate which is inert so as not to interfere with any sample and not to suppress any sample;
(2) mounting the substrate in a fixed retaining means, to hold the substrate stationary and to present the substrate for contact with an object;
(3) presenting an object to the substrate and rubbing one side of the object against the substrate, to transfer a sample of trace particles and liquids onto the substrate; and (4) desorbing the trace particles and liquids into the inlet of an analyzer for analysis.

2. A method as claimed in claim 1, wherein the substrate is generally planar, and step (3) includes displacing a central portion of the substrate out of the plane of the substrate for contact with the object, whereby any sample is transferred to the central portion of the substrate.

3. A method as claimed in claim 2, wherein the substrate is mounted in a holder facing upwards and a central portion of the substrate is raised by means of a boss displaced relative to the holder.

4. A method as claimed in claim 2, when carried out using a substrate which shows no interference and no suppression to analytes of interest, is efficient at removal of a sample from an object, is not contaminated by contaminants commonly found in ambient air, readily desorbs a sample, and enables a sample to be desorbed by heating and vaporization, without degradation of the substrate.

5. A method as claimed in claim 4, when carried out using a substrate comprising at least one of glass fibre, Teflon, paper, cotton, linen, wool and silk, and wherein the substrate is porous or semiporous.

6. A method as claimed in claim 3, wherein the substrate is chemically treated to enhance the ability thereof to trap and transfer an analyte of interest.

7. A method as claimed in claim 3, wherein step (3) is carried out at a first location, and the substrate is then transferred to a second location adjacent the inlet of an analyzer, to carry out step (4).

8. A method as claimed in claim 7, wherein following step (4), the substrate is moved to a third location where it is permitted to cool, prior to returning to the first location to receive a further sample.

9. A method as claimed in claim 7, when carried out using a mechanical handling means which transfers the substrate between the first and second locations, whereby manual handling of the substrate is not required.

10. A method as claimed in claim 8, when carried out using a mechanical handling means which transfers the substrate between the first, second and third locations, whereby manual handling of the substrate is not required.

11. A method as claimed in claim 10, when carried out using a plate means mounted for rotation about a central axis and including at least three substrates, wherein the three locations are provided around the plate and substrates are moved between the locations by rotation of the plate.

12. A method as claimed in claim 11, which includes a fourth location into which each substrate is moved by the circular plate and at which fourth location each substrate is subject to an elevated temperature, to clean the substrate, the fourth location being provided between the second or third locations.

13. A method as claimed in claim 3, when carried out to detect the presence of an analyte comprising one of drugs, explosives and a known target substance.

14. A method as claimed in claim 3, when carried out using a sheet-form object.

15. A method as claimed in claim 14, when carried out using a travel document selected from tickets, boarding passes, passports and identification documents.

16. An apparatus for collecting from the surface of an object trace particles and liquid as an analyte for analysis, the apparatus comprising:
a transfer substrate which is generally planar;
a retaining means for holding the substrate stationary; and a displacement means for displacing a central portion of the substrate out of the plane thereof, to enable a side of the object to be rubbed against the central portion of the substrate, to transfer a sample of trace particles and liquids to the substrate.

17. An apparatus as claimed in claim 16, wherein the displacement means comprises a boss and a mechanism for displacing the boss generally perpendicularly relative to the substrate.

18. An apparatus as claimed in claim 17, wherein the boss presents a generally spherical surface for contacting and displacing the substrate.

19. An apparatus as claimed in claim 16, wherein the retaining means comprises a mechanical holder, and wherein the holder is adapted for movement between a first location in which the substrate is contacted with an object and a second location adjacent the inlet of an analyzer for desorption of a sample, and wherein the apparatus includes a mechanical handling means for moving the holder between the first and second locations.

20. An apparatus as claimed in claim 19, wherein the holder includes support rails to enable the holder to be displaced longitudinally between the first and second locations.

21. An apparatus as claimed in claim 19, wherein the mechanical handling means and the holder comprise a circular plate mounted for rotation about an axis and including a plurality of individual substrates mounted therein.

22. An apparatus as claimed in claim 21, wherein each substrate mounted in the circular plate is moveable into a third location, between the first and second locations, and in which a substrate is permitted to cool following desorption prior to returning to the first location.

23. An apparatus as claimed in claim 22, wherein the circular plate includes a fourth location in which the substrate is subjected to an elevated temperature to clean the substrate.

24. An apparatus as claimed in claim 19, wherein the mechanical handling means comprises an arm mounted for rotation about an axis and including a free-end portion on which the substrate is mounted, which free-end portion is moveable between the first and second locations, and an actuating handle attached to the arm for displacing the arm between the first and second locations.

25. An apparatus as claimed in claim 15, wherein the substrate is one of a porous and semiporous material and comprises one of glass fibre, teflon, paper, cotton, linen, wool and silk.