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WO2008054393A1 - Procédé et dispositif pour un échantillonnage et une détection sans contact - Google Patents

Procédé et dispositif pour un échantillonnage et une détection sans contact Download PDF

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Publication number
WO2008054393A1
WO2008054393A1 PCT/US2006/042863 US2006042863W WO2008054393A1 WO 2008054393 A1 WO2008054393 A1 WO 2008054393A1 US 2006042863 W US2006042863 W US 2006042863W WO 2008054393 A1 WO2008054393 A1 WO 2008054393A1
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Prior art keywords
gas
ions
ion
analyte
reactant
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Timothy P. Karpetsky
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EAI Corp
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EAI Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/622—Ion mobility spectrometry
    • G01N27/624—Differential mobility spectrometry [DMS]; Field asymmetric-waveform ion mobility spectrometry [FAIMS]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/34—Dynamic spectrometers
    • H01J49/42—Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons

Definitions

  • This invention relates to a method and apparatus for the direct, non-contact, real-time sampling and detection of minute quantities of materials on surfaces.
  • this invention relates to a method and apparatus for producing ions from targeted analyte molecules on or above a surface that is spaced apart from the apparatus and for detecting and identifying those ions, all without contacting the surface.
  • the present invention provides a complete means to scan surfaces such as paper, plastics, skin, glass and textiles from variable distances and determine in seconds if targeted chemicals or materials are present, completely independent of the vapor pressures of such chemicals.
  • Currently available detectors generally create ions of the vapors of targeted chemicals and other chemicals taken into the body of the detector, then separate the ions and detect, identify and provide notification of the presence of any targeted chemicals.
  • the present invention overcomes this limitation by creating ions from sample chemicals exterior to the detector, on surfaces, and draws these ions into the detector for separation, detection, identification and notification.
  • reactant ions are created within the detector from a constant supply of conditioned air or other gas. These reactant ions are focused and accelerated as they leave the detector.
  • the reactant ion stream impacts the chemicals on a surface exterior to the detector and creates surface sample chemical ions. These ions are drawn into another part of the detector, using electronic means to control ion movement and collection.
  • the surface sample chemical ions are separated from the ambient air in which they are collected, and simultaneously moved and concentrated in a stream of constant composition air. The ions are then detected and identified after movement into a micro differential mobility spectrometer having no moving parts and made much like an integrated circuit.
  • ion mobility spectrometers require an ion source, which may be a radioactive ionization source ( ⁇ -emitter or electron producer) such as 63 Ni.
  • a radioactive ionization source such as 63 Ni.
  • alternative ionization sources such as corona discharge ionization sources are preferred.
  • corona discharge is described in U.S. Patent No. 6,225,623. Corona discharge units have been and are widely used with helium gas to produce long-lived metastable helium atoms.
  • the source comprises a chamber having an inlet port and an outlet port for passage of a carrier gas, and a pair of electrodes arranged to create a corona discharge within the chamber.
  • the carrier gas helium or nitrogen
  • the carrier gas is passed through the corona discharge causing formation of, among other species, neutral, excited state, metastable species of the carrier gas.
  • Those excited state carrier gas molecules upon leaving the device then contact the sample, or analyte, and by transfer of energy from the excited state carrier gas molecules to analyte molecules, produce analyte ions.
  • the analyte ions in the carrier gas are then passed to a charged particle or ion sensor, which may be the sensing element of a mass spectrometer or an ion mobility spectrometer.
  • a charged particle or ion sensor which may be the sensing element of a mass spectrometer or an ion mobility spectrometer.
  • the helium metastable atoms leave the confines of the device and subsequently react with surface materials to produce surface sample ions.
  • the neutral helium metastable and energetic atoms, freed of any ions produced in the corona discharge by ion filters, are then reacted with the chemical components of air or other gases such as dopants, introduced within the device, causing the formation of reactant ions, such as O 2 " and HaO + , and electrons within the device.
  • neutral metastable helium atoms can interact with other metastable atoms and with neutral ground state atoms to produce charged species. So, even if ion filters are used at this stage, ions can still be produced.
  • filters are used at this stage, they remove the ions produced during passage of the gas through the corona discharge. Subsequent charged species production results only from the interactions noted above.
  • ions produced in the corona discharge, along with energetic neutral species are reacted with the chemical components of air or other gases, introduced within the device, causing the formation of reactant ions, such as O 2 " and H 3 O + , and electrons within the device.
  • automated distance information from a rangefinder can provide feedback control to the ion focusing and accelerating portions of the invention.
  • the reactant ions created within the invention can be focused on a surface such that the same amount of ions per unit area hit the surface independent of the distance between the detector and the surface. This allows the operator freedom of movement of the detector away from and towards the surface with assurance that, regardless of position, the same amount of detector initiated reactant ions will generate the same amount of sample ions on the surface, and ultimately, the same sensor-driven signal within the detector.
  • the reactant ions created within the invention are those well known to react with a wide variety of chemicals of interest, to form predominantly molecular ions. Molecular fragmentation is kept to a minimum in this "soft" ionization process. This greatly simplifies the detection and identification process.
  • the reactant ions emitted from the detector can be confined within a sheath gas such that, in the transit between detector and surface, the integrity of the detector originated ion population is largely maintained and admixing with the ambient air between the detector and the surface sample is kept to a minimum.
  • IMS ion mobility spectrometry
  • the first, or reaction, region contains the ionization source and is separated from the drift region by an electrical shutter or ion gate.
  • the sample molecules are directly subjected to the ionization source and, depending upon the sample and the intensity of the source, a wide variety of molecular fragments, as well as simple ions, are produced.
  • the mixture of reactant and product ions reaches an ion gate that separates the reaction region and the drift region.
  • the ions With a bias voltage applied, the ions are attracted to the ion gate and lose their charge. Then the bias is briefly turned off, and ions are transmitted into the drift region of the cell.
  • ion mobility spectrometers may be usefully employed with the ion source of this invention to produce portable, non-contact sampling systems.
  • Another charged particle or ion sensor that is coming into use employs differential mobility spectrometry (DMS).
  • DMS differential mobility spectrometry
  • An example of a differential mass spectrometer is the MicroDMx manufactured by Sionex Corporation. This device has no moving parts and is microfabricated. Its small size allows for extremely fast clear down times and very rapid responses to the presence of ions.
  • selectivity is significantly enhanced relative to other techniques of ion resolution and detection.
  • DMS exploits the way in which the mobility of ions changes in response to changes in an applied variable high electric field, and this provides substantially more information relating to a molecule's identity than other methods, consequently leading to a significant reduction in false positives.
  • Differential mobility spectrometry can detect positive and negative ions simultaneously and has superior sensitivity and selectivity capabilities relative to more commonly used sensors such as ion mobility spectrometers.
  • DMS achieves superior selectivity relative to simple time- of-flight information employed in other detectors by using placement of ions within four-dimensional space constructed to examine changes in ion mobility as a function of changes in high electric field strength. Detection and identification are rapidly made and notification of presence or absence of targeted materials given in near-real time.
  • Sensitivity is enhanced as well because as a range of compensation voltages in a DMS device are scanned the actual percentage of ions detected for any type of ion species is significantly higher (>10x) than in conventional IMS.
  • DMS Downlink Detection of such materials must be rapid, but also must be done with virtually no false negatives such that-these materials go undetected when actually present, creating a potentially dangerous situation. There must also be virtually no false positives such that materials are detected when none are present, thereby closing down the checkpoint while the false positive is verified as erroneous.
  • the selectivity of DMS for certain materials such as explosives can be enhanced by transferring ions from an incoming ambient air stream to an air stream of controlled composition, possibly containing a dopant chemical to further control the nature of the ion species in the stream. Having considered the ion production and ion detection portions of the invention, it is then necessary to manage, in a complementary manner, the movement of the reactant ions from the detector to the surface and the subsequent collection and concentration of surface sample ions in another part of the detector in order to most efficiently use the ions produced within the invention and in order to maximize sensitivity of the invention.
  • Issuing reactant ions of alternating charges as a function of time from the ion production device and biasing the ion outlet to the same charge of the reactant ions so the ions are "pushed" away from the ion outlet and towards the surface can accomplish this.
  • the ion collection device undergoes programmed biasing aimed at providing sufficient charge opposite to that of the produced surface sample ions, thereby "pulling" these ions toward the collection device and into the sensor for detection and identification.
  • the maximum possible number of collected ions must reach the sensor to attain the highest sensitivity.
  • the ions are focused such that they are transported without touching the walls.
  • such feedback can be used, in conjunction with the distance from the detector reactant ion production device to the surface (provided by a rangefinder) to control the timing of changes of potential applied to the ion collection inlet, relative to those changes of potential controlling the production of reactant ions, as the distance between the detector and surface is changed.
  • This has the practical effect of providing assurance that relatively the same number of ions is detected by the detector as it is moved toward or away from the surface. The operator, therefore, does not have to keep the detector at a fixed distance from the targeted surface and allows for freedom of movement of the detector toward or away from the surface with assurance that targeted surface materials will still be detected with relatively the same certainty.
  • feedback control without using the rangefinder but using the DMS signal, can be used to control the density of reactant ions projected from the ion production means, thereby controlling the overall sensitivity of the detector.
  • a means to generate ions of targeted chemicals on surfaces coupled with a small fast sensor with excellent sensitivity and selectivity, and the means to use distance and sensor information as feedback to control the entire process provides the elements of a detector that can be used to close security loopholes. It will enable the rapid screening of the surfaces of people, baggage, cargo, parcels and vehicles at government and private facilities, transportation centers, checkpoints and borders, among others. It will also find use in substantiating illegal activities by facilitating the rapid and accurate detection of chemical warfare agents (CWAs), explosives and illicit substances and to verify decontamination efforts are successful by military personnel.
  • CWAs chemical warfare agents
  • Key features of the invention are means to control, focus and accelerate the detector originated reactant ions responsible for producing surface sample ions from chemicals on surfaces, and the coordination of these events with the rapid collection of the surface originated ions in high yields for detection and identification by the sensor.
  • the capability to apply roughly the same amount of reactant ions to the same surface area regardless of the distance of the detector from the surface allows the operator to scan the surface from variable detector - surface distances and obtain the same result, rather than be constrained to holding the detector at a fixed, close distance from the surface.
  • an ion production and sensor system that operates by impacting a reactant ion stream upon a surface to form ions of sample compounds carried on that surface, to collect at least some of the sample ions that are formed, and to pass those ions into, for example, a differential mobility spectrometer to identify and quantify the sample compounds.
  • Another object of this invention is to provide an extremely sensitive, fully portable, hand-held detector that can identify and quantify compounds such as drugs and chemical warfare agents in place on surfaces without physical contact of those surfaces.
  • Yet another object of this invention is to detect equally well the presence of an analyte that comprises sample compounds having extremely low or hugely different vapor pressures without physical contact of the surface that carries the analyte or sample compounds.
  • the detector system of this invention includes two major parts.
  • First is a reactant ion production device having the capability to produce reactant ions from introduced air or other gases, and to filter, focus and accelerate such reactant ions constrained within a sheath gas or not as appropriate, toward a surface, generating surface sample ions from the chemicals on that surface.
  • Second is an ion collection device that collects surface sample ions produced by the interaction of reactant ions with sample chemicals on the surface.
  • the ion collection device has the capability to transfer such sample ions from the ambient air in which they are collected to a controlled air stream, to introduce reactant gases or dopants that can modify the structure, charge and/or adduct formation or dissociation of the sample ions, and to introduce the ions into a differential mobility spectrometer. Events in the ion production and ion collection devices are fully coordinated to maximize sample ion production and collection. Feedback controls, using information from a rangefinder and the spectrometer or sensor, enable similar ion detection results to be obtained regardless of the distance between the detector and the surface.
  • Figure 1 is a schematic representation showing the arrangement of the reactant ion production and surface sample ion collection, detection and identification means according to this invention
  • Figure 2 is a schematic representation of a first reactant ion production means of the Figure 1 system
  • Figure 3 is a schematic representation of another embodiment of the reactant ion production means of Figure 2;
  • Figure 4 is another embodiment of the reactant ion production means of
  • Figures 2 and 3 including a means for concentrating ions and changing the ion carrier gas as is illustrated in Figure 8;
  • Figure 5 is a cross sectional view of the ion production means of Figure 4 taken along line 5 - 5';
  • Figure 6 is a diagrammatic representation of a surface sample ion detection and identification means according to the present invention
  • Figure 7 is a partial, cross sectional representation of the surface sample ion detection and identification means of Figure 6;
  • Figure 8 is a cross-sectional representation of an ion inlet arranged with a surface sample ion concentration and change of ion carrier gas means for use with the detection and identification means of Figures 6 and 7;
  • Figures 9a through 9d depict the first half of a cycle of the production of ions, showing the production of negatively charged reactant ions, creation of negatively charged surface sample ions and collection of such surface sample ions using the reactant ion production means of Figures 2, 3 and 4, and the surface sample collection, detection and identification means of Figures 7 and 8 when operated in a pulsed mode;
  • Figures 10a through 10d depict the second half of a cycle of the production of ions, showing the production of positively charged reactant ions, creation of positively charged surface sample ions and collection of such surface sample ions using the reactant ion production means of Figures 2 3 and 4, and the surface sample collection, detection and identification means of Figures 7 and 8 when operated in a pulsed mode;
  • Figure 11 is a generally schematic diagram of the arrangement of components in an operating system for a detector according to the teachings of this invention.
  • this invention can be viewed as a method and means for conducting a three-step energy transfer process that may then be followed by an analytical procedure.
  • Energy is applied to a first gas by means of a corona discharge, forming ions and other energetic species of that gas.
  • the energetic species of the first gas then transfer energy to a second gas, which must have at least one component with an ionization potential, or ionization energy, less than that of the energetic species of the first gas so as to produce reactant ions of the second gas.
  • Those reactant ions are caused to impact upon a surface, reacting with chemicals or other materials on the surface to produce analyte ions that are collected, detected and identified.
  • a significant advantage of this downhill energy flow is that it utilizes energy from an inexpensive, relatively uncontrolled high energy source (corona discharge) and converts it into energetic species that provide a "soft 1 ionization of analytes. That is, the reaction of Gas 2 reactant ions with analytes produces mainly molecular ions rather than ionized structural fragments. This simplifies the detection and identification process in a wide variety of situations.
  • Selectivity can be achieved by changing the gas from air to other gases having different ionization potentials, such as ammonia, 10.2e.V.; acetone, 9.7e.V.; or di n-propylamine, 7.8e.V.
  • Reactant ions from each of these gases would ionize organic chemicals having ionization potentials less than that of the respective gas. This provides for selectivity based on ionization potential.
  • the gas ions or neutral species can combine with the surface analyte ions to produce ion/molecular clusters that can aid in analyte ion identification and separation.
  • Electronic potentials at different places are used to manipulate the types and populations of reactant ions formed and issued from the reactant ion production device and of the types and populations of surface sample ions collected by the surface sample ion collection device. Also, real-time distance of detector to surface information, and detector sensor information provide automatic feedback control of these potentials. This feedback control manages and maximizes the instantaneous active interplay between the detector and the surface sample under investigation. On one hand, the reactant ion density put on the surface sample is maintained relatively constant and independent of working distance between the detector and the surface sample. On the other, the collection efficiency of the surface sample ion collector is optimized and collected ion loss prior to entry into the sensor is minimized. These events are automatically managed and coordinated such that operator input to the process is not necessary.
  • the detector system 10 of Figure 1 operates at ambient pressure, without sample contact, by producing a stream 12 of either ions or a mixture of ions and metastable excited state molecules, in ion production means 14.
  • Stream 12 is then directed toward an analyte, or sample material 15, in place on surface 16, to produce ions of the sample material, some of which are detached from the surface and admixed with the gas adjacent the surface.
  • a stream of gas is then pulled into a port means 18 of ion collection means 80 leading to ion detection and identification means 20 by action of pump 22.
  • ion production means 14 which suitably may be constructed as a cylinder having a wall member 120 and arranged for generally axial flow of gases therethrough.
  • a corona discharge is produced at the upstream end by ion production means 14 in space 24 located between corona discharge needles 26 and corona disk electrode 27.
  • a pair of filtering electrodes, 33 and 34 is placed just downstream from the corona discharge. One of those electrodes is positively charged and the other negatively charged and the two serve to remove ions that were created in the corona discharge area but do not interact with the metastable atoms as those carry no charge.
  • a reaction space 37 is provided just downstream from filtering electrodes 33 and 34 wherein gas stream 29, carrying excited metastable atoms, mixes with a second gas stream 39 entering into space 37 by way of port 41.
  • Second gas stream 39 is preferably air, including clean dry air from a filtering device containing dessicant, but may comprise other gases or mixtures of gases depending upon the application.
  • Metastable atoms of first gas 29 react with the second gas 39 to produce an array of positive and negative ions.
  • the ions that are produced in space 37 are then accelerated in a downstream direction and focused into a coherent stream by action of electrodes 35, 151, 153 and 155.
  • a space 150 is provided adjacent the terminal end of the ion production means.
  • Space 150 contains a plurality of accelerating and focusing electrodes 35, 151 , 153, and 155 ( Figure 4), that cause the ion stream to exit the ion production means 14 at port 51 as a tight, coherent conical beam 12.
  • the terminal portion of space 150 is advantageously formed with a conical tapered wall 165 that regularly decreases in diameter from the inner side of wall member 120 to the exit port 51. That structure forms a manifold 167 around the outside of wall 165 which functions to provide a flow of gas 169 from inlet 175 through a ring orifice 171 that encircles the exit port 51, producing a generally conical gas sheath that surrounds the ion stream.
  • Gas flow 169 provides a protective sheath that helps to prevent reaction of the ion beam 12 with contaminant compounds.
  • Figure 3 depicts an embodiment of the ion production means 14 in which the central portion 46 is formed as a venturi so that an air stream is drawn through port 41 into the body of means 14 by the reduced pressure created by flow of first gas stream 29 through venturi area 46.
  • a filter means 47 having an entry 48 and preferably containing a desiccant, is located upstream from port 41 so as to provide a dean air stream of uniform humidity to the ion production means. Water vapor is ionized by the excited species produced in the corona discharge so variations in humidity in the air entering means 14 can introduce undesirable variations in the ion population discharged from the unit.
  • Figures 4 and 5 Yet another embodiment of the ion production means 14 is illustrated in Figures 4 and 5.
  • Figure 5 is a cross-section taken along line 5 - 5' of Figure 4.
  • Means 14, in this embodiment, includes ion concentration and gas exchange means, located centrally between reaction space 37 and terminal end space 150, that serve to strip ions from the helium stream and transfer those ions to a different gas, which suitably is purified air which may contain a dopant chemical to influence the nature of the ions.
  • the ion concentration and gas exchange means is provided with a cylindrical outer wail 122, a central, axially aligned electrode carrier 125, and a cylindrical partition member 127 that serves to form a first annular space 129 that is open at its upstream end to accept the mixed and reacted gas from space 37.
  • a second annular space 131 is formed between partition member 127 and axial electrode carrier 125.
  • Partition member 127 is provided with two ports 133 and 135 that conveniently may be placed opposite one another to allow ion and gas flow between the first and second annular space.
  • a pair of electrodes 137 and 138 having the same polarity as the incoming ions contained in the gas issuing from space 37, is located on the inner side of wall 122 within annular space 129 just opposite ports 133 and 135.
  • An electrode 141 of opposite charge to electrodes 137 and 138, is located on electrode carrier 125 in alignment with ports 133 and 135. As the ions in the gas stream within annular space 129 approach electrodes 137 and 138, they are directed toward and through ports 133 and 135. At the same time, the ions are attracted toward electrode 141 which tends to pull ions from the gas in space 129, through the ports, and into annular space 131.
  • a flow of gas is continuously introduced into annular space 131 by way of entry 143 that is located upstream of ports 133 and 135.
  • the ion-depleted gas stream is exhausted to the atmosphere by way of exhaust port 145 that is located downstream of ports 133 and 135 while the ion- enriched gas stream exits annular space 131 into the ion accelerating and focusing space 150.
  • the relative cross sectional areas of annular spaces 129 and 131 and the flow rates of the gas streams in those annular spaces can be adjusted such that the ion concentration in the gas within annulus 131 is substantially greater than that of the gas in annulus 129.
  • the ion stream produced may be either positive or negative depending upon the polarity applied to the various electrodes.
  • a preferred embodiment of this invention employs a laser, or other type of, range finder 49 that is mounted in fixed association with ion production means 14.
  • This embodiment is especially desirable in those instances wherein the device of this invention is configured as a compact, light, hand-held detector system for use in screening individuals, luggage, clothing and similar items without physical contact of any sort.
  • Range finder 49 continuously determines the distance between the exit port 51 of the ion production means and the surface sample 15.
  • Information stream 52 from the range finder is transmitted to processing unit 53 which may then use that information to adjust the focusing and acceleration functions of electrodes 35, 151 , 153, and 155, so as to maintain the area of surface 16 impacted by the conical ion beam relatively constant as the distance between exit port 51 and surface sample 15 is changed. That result is accomplished by increasing the apex angle of the ion beam at short distances, on the order of an inch or so, between port 51 and surface sample 15, and decreasing the apex angle at greater distances, up to five to six inches between the port and surface sample.
  • Ion detection and identification means 20 is preferably a miniaturized differential mobility spectrometer that is schematically illustrated in Figures 6 and 7 of this application and that is described in U.S. Patent No. 6,512, 224 to Miller et al, the entire disclosure of which is incorporated herein by reference.
  • the differential mobility spectrometer that is described in the Miller et at patent is commercially available from Sionex Corporation. It is microfabricated in a manner analogous to the manufacture of a printed circuit and is in the form of a planar array having an overall size on the order of 36 x 72 mm, with a plate spacing of about half a millimeter.
  • Detector 20 is shown in schematic cross-section in Figures 6 and 7 and comprises a microfabricated planar array that forms an ion filter having no moving parts.
  • a stream of ions 60 carried in a gas, is flowed between filter plates 62 and 63 of sensor 20.
  • An asymmetric oscillating RF field 65 is applied perpendicular to the ion flow path 67 between filter plates 62 and 63 to impart a zigzag motion ( Figure 6) to the ions.
  • a DC compensation voltage is applied between plates 62 and 63 to control the motion of the ions such that some travel all the way through the plate array and are detected by electrodes 70 and 71, while others are directed to one or the other of plates 62 and 63 and are neutralized.
  • Two or more detector electrodes are located downstream from the filter plates.
  • Electrode 70 deflects ions downward to electrode 71 where they are detected.
  • either electrode 70 or electrode 71 may be used to detect ions or multiple ions may be detected by using electrode 70 as one detector and electrode 71 as a second detector. In this way, both positively and negatively charged ions can be detected simultaneously.
  • the output of the detector electrodes is transmitted to an electronic controller 75 where the signal is amplified and analyzed according to algorithms that serve to identify the ion species.
  • an entry port electrode 77 to which either a positive or negative charge may be applied so as to attract oppositely charged ions toward and into the ion detection means 20.
  • ion detection sensitivities may be increased as much as 10-fold or more through use of an ion inlet and concentration means 80 shown in diagrammatic cross section in Figure 8.
  • This device may comprise port means 18 of Figure 1, and includes the functional equivalent of the ion concentration and gas exchange means employed in the ion production device that was illustrated in Figures 4 and 5. It serves to draw sample ions into the inlet and to change the gas containing the ions from ambient air collected at and near the sample and of uncontrolled composition, to air or other gas of defined composition, alone or in combination with other gases, including dopants such as methylene chloride and the like, which can be ionized using a very small UV lamp elsewhere in the detector.
  • dopants such as methylene chloride and the like
  • [Means 80 includes an inlet portion 201 that comprises a conduit having an upper wall 82 and a lower wall 84.
  • a conductive, apertured entry 203 is provided at one end of the conduit to which a polarity and potential sufficient to attract the incoming ions contained in adjacent reaction cloud 111 is applied.
  • Electrodes 206 and 207 are disposed around the inner periphery of conduit 201 just downstream of entry 203 and are of polarity and potential sufficient to attract and focus incoming surface analyte ions.
  • the potential applied to entry 203 and to electrode 206 are similar and that of 207 is higher.
  • Additional electrodes 209 and 210 are disposed around the inner periphery of conduit 201 further downstream from the entry. These last electrodes carry a controllable potential that is of the same polarity as is the incoming ion stream and serve to focus the ions into the central area of the conduit.
  • Reaction cloud 111 comprises a mixture of the gas issuing from the ion production means 14 and the ambient atmosphere, and contains sample ions formed by interaction of energetic ions from means 14 with sample materials 15 in place on surface 16.
  • a stream of gas 91, comprising reaction cloud 111, is drawn through conduit 201 by action of pump 22 ( Figure 1), and the ion concentration in that gas stream is increased due to the attractive influence of the potential field created by the charge applied to inlet 203.
  • the gas exchange portion of means 80 comprises a two-chamber conduit formed by a partition wall portion 85 that is disposed exterior to and generally parallel with conduit walls 82 and 84.
  • An orifice 87 located between the chamber ends is arranged to allow gas flow between upper chamber 88 and lower chamber 89.
  • a flow of ions in the ambient sample atmosphere 91 is directed into the entry of the upper chamber 88.
  • the ambient sample atmosphere with ions removed exhausts from the chamber 88 end at 92.
  • a second gas stream 94 for example, suitably preconditioned dry air, is directed into the entry of the lower chamber 89.
  • Gas stream 94 passes through chamber 89 and the exiting flow 95 is then directed into the entry of ion detection means 20.
  • the cross sectional area of chamber 88 relative to chamber 89 and the flow rate of sample atmosphere 91 relative to the flow rate of the second gas stream 94 are adjusted such that there is a small and constant bleed 97 of gas from the lower chamber 89 into the upper chamber 88 through the orifice 87.
  • a first electrode 98 having the same polarity as the incoming ions in sample stream 91 is located within chamber 88 above the orifice 87, while a second similar electrode 99, having a polarity opposite to the incoming ions, is located within chamber 89 below the orifice.
  • a second similar electrode 99 having a polarity opposite to the incoming ions.
  • the ions in sample stream 91 approach electrode 98, they are repelled and are directed toward and through orifice 87.
  • the ions are attracted toward electrode 99, which tends to pull ions from sample stream 91 through the orifice and into gas stream 94.
  • a concomitant concentration of ions in stream 94 is achieved.
  • a concomitant concentration of ions in stream 94 is achieved.
  • ion concentration there is achieved a fairly complete elimination of helium or argon from the gas stream that enters sensor 20 in those situations where either helium or argon is present in the reaction cloud 111.
  • a preferred ion detector 20 is a microfabricated differential mobility spectrometer that typically has a plate spacing on the order of half a millimeter.
  • That small plate spacing allows use of much higher electric fields than are usual in other detector systems such as those employing ion mobility spectrometers; e.g. as high as about 35,000 V/cm compared to about 600 V/cm.
  • Higher variable electric fields allow the changes in the mobility of ions as a function of field strength to be exploited to enhance selectivity and resolution.
  • the maximum electric field is limited by the voltage at which arcing between the plates occurs with resultant destruction of the detector.
  • Arc over occurs at a much lower voltage with helium or argon than with air. Consequently, removal of helium and argon from the sample gas stream that is analyzed allows for operation of the detector at higher field voltages thus further increasing the selectivity of the system.
  • the ion production means of this invention does not use radioactive elements for ion creation and is therefore free of the regulatory burden imposed on devices employing radioactive sources.
  • the corona discharge production of metastable helium atoms followed by the reaction of those metastable atoms with air to produce ions which in turn are used to ionize molecules of the sample is on the order of 1000 times more efficient than are those approaches that use the standard radioactive nickel or americium sources.
  • the system of this invention creates far more ions of the sampled material than do conventional ion sources and because the preferred detector examines far more of the ions that are produced, fewer false positives or negatives result and superior resolution of targeted chemical ions from interferents is obtained.
  • both the ion source and the ion collection means and detector are operated in a pulsed cyclic mode.
  • ion production and collection can be seen as two half cycles, the first half cycle being diagrammed in Figure 9 and the second half cycle being diagrammed in Figure 10.
  • a gas stream 101 carrying negatively charged reactant ions issues from the outlet 51 of the ion production device 14 and is directed toward surface 16 having a sample material 15 deposited thereon. Stand off distance between outlet 51 and surface 16 may conveniently range from less than one inch to six inches or more, thus allowing a non-contact and non-destructive inspection of the surface for the presence of the sample material.
  • Ion production device 14 is configured to produce reactant ions of predominately one charge; in this case it is producing negative ions.
  • a negative potential is applied to an electrode 106 that is located at the tip of outlet 51. That negative charge acts to accelerate the negative ions contained in the gas stream issuing from outlet 51 toward surface 16.
  • a similar electrode 108 is located at the tip of ion collection means and/or detector inlet 109.
  • Inlet 109 may comprise either the inlet to ion detection means 20, in which case electrode 77 of Figure 7 and electrode 108 are the same, or it may comprise an inlet means 203 to ion concentrator 80 of Figure 8.
  • the potential on electrode 108 at this stage of the cycle is zero or ground potential.
  • the negative pressure at the detector inlet 109 may be decreased during this time so as not to pull gas and ions from stream 101 toward the detector inlet.
  • Electrode 106 remains at a negative potential and electrode 108 remains at zero potential.
  • a reaction cloud 111 typically comprising a mixture of air and helium and containing negatively charged surface sample ions, among other species has formed above the surface that is being examined.
  • the reactant ion production pulse has ended.
  • a negative potential is maintained on electrode 106 while the potential on electrode 108 is changed from zero to positive and the negative pressure at the detector inlet is increased.
  • Electrode 108 is shaped and charged to produce an electric field that has the effect of drawing the ions in reaction cloud 111 toward the detector inlet.
  • the ion loud reaches electrode 108 its potential can be switched from positive to neutral so as to not destroy the oncoming negative ions by collision.
  • the potential on electrode 108 can be left on and the collisions of ions with walls avoided by focusing the ions within the ion collection means as shown in Figure 8.
  • the negative pressure at the ion inlet is increased to thereby capture much of the ion cloud and deliver it as a pulse to the ion detector.
  • the ion cloud pulse is delivered first to ion concentrator 80 and then to the differential mobility spectrometer.
  • the second half cycle is the obverse of the first half cycle, and is diagrammed in the steps shown in Figures 10a through 10d.
  • Ion production device 14 is now configured to produce positive reactant ions, which are carried in the helium stream 101 issuing from outlet 51.
  • the potential applied to electrode 106 remains positive throughout the entire half cycle, first accelerating positive ions toward the surface 16 and thereafter repelling the reaction cloud 111.
  • Flow of the reactant ion stream 101 is ended after formation of the reaction cloud.
  • the potential applied to electrode 108 is briefly switched to negative ( Figure 10c).
  • the shape and charging of electrode 108 is sufficient to attract positive ions, including those formed from the sample material 15, toward inlet 109.
  • a negative pressure is applied to inlet 109, drawing the reaction cloud toward and into the inlet.
  • the potential of electrode 108 can be then switched from negative to neutral ( Figure 10d) before the ion cloud reaches the electrode so as to minimize destruction of the positive ions.
  • the potential on electrode 108 can be left on and the collisions of ions with walls avoided by focusing the ions within the ion collection means as shown in Figure 8.
  • the reaction cloud is delivered as a pulse to the ion concentrator or detector.
  • Cycle length can be varied over a fairly large range as the time for completing a cycle depends upon a number of controllable factors. Those factors include standoff distance between the ion outlet and the sample surface, gas flow rate delivered by the ion production means, and the configuration of the gas exit orifice.
  • a cycle can be completed in as little as 0.5 seconds or extended to several seconds in length. It is usually advantageous to maintain cycle times as short as possible.
  • Cycle time can be controlled by feedback from the differential mobility spectrometer. The timing of detection of certain reactant ions indicates the place in the cycle, allowing for automatic adjustment of the controls determining cycle time.
  • FIG. 11 is a schematic diagram of one embodiment of this invention in which all of the system components are assembled as a fully portable, hand-held detector 180 that contains its own helium supply.
  • a subassembly 183 that includes those components within the dashed line 182 defines a common platform that can be used for each of the different configurations of the system.
  • This common platform includes air and helium valving and gas flow control means 184, reactant ion production means 14, sample ion collection, detection and identification means 20, and an operator interface and control unit 186.
  • An on-board helium supply 190 conveniently in the form of a disposable cartridge containing pressurized gas, provides an adequate supply for a limited number of analyses and thus is suitable for use by first responders, law enforcement and military personnel.
  • a computer 192 together with its operating software controls the functioning of the system including helium and air flows and the operating parameters of the reactant ion source 14 that in turn depend upon whether the system is being operated in a continuous or in a cyclic mode.
  • the computer also uses information from rangefinder 49 (standoff distance from the ion source outlet to the surface that is being investigated) and sensor information to control reactant ion production and surface sample ion collection to maximize both.
  • the software carried in computer 192 employs a number of different algorithms to distinguish between and to identify ions and charged molecular fragments that result from the impingement of reactant ions, in ion stream 101, upon a surface 16 that has deposited thereon chemical compounds or other agents of interest or concern.
  • a number of different algorithms are carried in the computer, a different algorithm for each of different classes of materials.
  • algorithm 1 is specific to chemical warfare agents
  • algorithm 2 is specific for explosives
  • algorithm 3 is specific for drugs of both the prescription and illegal varieties
  • algorithm 4 is specific for toxic industrial chemicals and other toxic industrial materials.
  • the system also requires a power source 195 that may include both batteries and a transformer-inverter for AC use.
  • Readout means 198 is arranged to report the results of an analysis, and may be adapted to provide data either in visual form or as a printout. All of the system components reside within a case 199, which can be easily carried and maneuvered during use.
  • This configuration is especially advantageous for use at security and transportation checkpoints to monitor people, baggage, cargo, and material surfaces, as well as for the examination of baggage or incoming deliveries on conveyor belts, and for military, law enforcement, prison and industrial monitoring.
  • the common platform in whole or in part, and in conjunction with other parts of this configuration, can be used to examine items passing before it, whether such item be baggage or industrially produced items such as pharmaceuticals in order to determine the presence or absence of certain target chemicals in each different use.
  • the system can be deployed as a non-portable, bench top detector mode. This arrangement is particularly useful in those applications requiring high volume examination or scanning of field-collected samples, or in those instances in which a detailed scanning and examination of suspect objects is needed

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Health & Medical Sciences (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

Abstract

L'invention concerne un système (10) pour la détection à distance de sécurité de quantités traces de matériaux analytes tels des explosifs, des agents de guerre chimiques, des produits chimiques industriels toxiques et autres produits similaires, comprenant une source d'ions (14) qui est connectée de manière opérationnelle à un moyen de collecte d'ions (80) et à un capteur (20). La source d'ions (14) utilise un premier gaz qui passe à travers une décharge électrique pour produire des molécules de gaz métastables, de même que des particules chargées de différents types. Des ions et d'autres particules chargées sont enlevés du premier gaz qui est ensuite mis à réagir avec un second gaz ayant un potentiel d'ionisation inférieur, pour obtenir des ions réactifs d'une énergie relativement uniforme. Les ions réactifs sont focalisés et accélérés dans un faisceau (12) qui est dirigé sur une surface (16), telle un bagage ou un vêtement qui doit être examiné, pour produire des ions analytes qui sont captés et transférés dans le capteur (20), qui est de préférence un spectromètre à mobilité différentielle.
PCT/US2006/042863 2006-11-02 2006-11-02 Procédé et dispositif pour un échantillonnage et une détection sans contact Ceased WO2008054393A1 (fr)

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US11424116B2 (en) 2019-10-28 2022-08-23 Ionsense, Inc. Pulsatile flow atmospheric real time ionization
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US8421005B2 (en) 2006-05-26 2013-04-16 Ionsense, Inc. Systems and methods for transfer of ions for analysis
US8440965B2 (en) 2006-10-13 2013-05-14 Ionsense, Inc. Sampling system for use with surface ionization spectroscopy
US8207497B2 (en) 2009-05-08 2012-06-26 Ionsense, Inc. Sampling of confined spaces
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US10643834B2 (en) 2009-05-08 2020-05-05 Ionsense, Inc. Apparatus and method for sampling
US10090142B2 (en) 2009-05-08 2018-10-02 Ionsense, Inc Apparatus and method for sampling of confined spaces
US8895916B2 (en) 2009-05-08 2014-11-25 Ionsense, Inc. Apparatus and method for sampling of confined spaces
US9633827B2 (en) 2009-05-08 2017-04-25 Ionsense, Inc. Apparatus and method for sampling of confined spaces
US9390899B2 (en) 2009-05-08 2016-07-12 Ionsense, Inc. Apparatus and method for sampling of confined spaces
US8822949B2 (en) 2011-02-05 2014-09-02 Ionsense Inc. Apparatus and method for thermal assisted desorption ionization systems
US9224587B2 (en) 2011-02-05 2015-12-29 Ionsense, Inc. Apparatus and method for thermal assisted desorption ionization systems
US8963101B2 (en) 2011-02-05 2015-02-24 Ionsense, Inc. Apparatus and method for thermal assisted desorption ionization systems
US9514923B2 (en) 2011-02-05 2016-12-06 Ionsense Inc. Apparatus and method for thermal assisted desorption ionization systems
US11742194B2 (en) 2011-02-05 2023-08-29 Bruker Scientific Llc Apparatus and method for thermal assisted desorption ionization systems
US11049707B2 (en) 2011-02-05 2021-06-29 Ionsense, Inc. Apparatus and method for thermal assisted desorption ionization systems
US8754365B2 (en) 2011-02-05 2014-06-17 Ionsense, Inc. Apparatus and method for thermal assisted desorption ionization systems
US9960029B2 (en) 2011-02-05 2018-05-01 Ionsense, Inc. Apparatus and method for thermal assisted desorption ionization systems
US10643833B2 (en) 2011-02-05 2020-05-05 Ionsense, Inc. Apparatus and method for thermal assisted desorption ionization systems
US9105435B1 (en) 2011-04-18 2015-08-11 Ionsense Inc. Robust, rapid, secure sample manipulation before during and after ionization for a spectroscopy system
US8901488B1 (en) 2011-04-18 2014-12-02 Ionsense, Inc. Robust, rapid, secure sample manipulation before during and after ionization for a spectroscopy system
EP2951569A4 (fr) * 2013-01-31 2016-09-21 Smiths Detection Montreal Inc Source pour ionisation de surface
US9337007B2 (en) 2014-06-15 2016-05-10 Ionsense, Inc. Apparatus and method for generating chemical signatures using differential desorption
US10825675B2 (en) 2014-06-15 2020-11-03 Ionsense Inc. Apparatus and method for generating chemical signatures using differential desorption
US10553417B2 (en) 2014-06-15 2020-02-04 Ionsense, Inc. Apparatus and method for generating chemical signatures using differential desorption
US9558926B2 (en) 2014-06-15 2017-01-31 Ionsense, Inc. Apparatus and method for rapid chemical analysis using differential desorption
US10056243B2 (en) 2014-06-15 2018-08-21 Ionsense, Inc. Apparatus and method for rapid chemical analysis using differential desorption
US11295943B2 (en) 2014-06-15 2022-04-05 Ionsense Inc. Apparatus and method for generating chemical signatures using differential desorption
US9824875B2 (en) 2014-06-15 2017-11-21 Ionsense, Inc. Apparatus and method for generating chemical signatures using differential desorption
US10283340B2 (en) 2014-06-15 2019-05-07 Ionsense, Inc. Apparatus and method for generating chemical signatures using differential desorption
US9899196B1 (en) 2016-01-12 2018-02-20 Jeol Usa, Inc. Dopant-assisted direct analysis in real time mass spectrometry
US10947382B2 (en) 2016-09-28 2021-03-16 Shpp Global Technologies B.V. Phenylene ether copolymer and compositions comprising same
US10636640B2 (en) 2017-07-06 2020-04-28 Ionsense, Inc. Apparatus and method for chemical phase sampling analysis
US10825673B2 (en) 2018-06-01 2020-11-03 Ionsense Inc. Apparatus and method for reducing matrix effects
US11424116B2 (en) 2019-10-28 2022-08-23 Ionsense, Inc. Pulsatile flow atmospheric real time ionization
US11913861B2 (en) 2020-05-26 2024-02-27 Bruker Scientific Llc Electrostatic loading of powder samples for ionization

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