Method and system for trace detection of low volatile substances

A system includes a conductive sampling swab including a non-mesh substrate and a thermal desorber including a clamping assembly configured to releasably hold the conductive sampling swab. The clamping assembly is configured to be electrically connected to a voltage or current source, and the thermal desorber is configured to resistively heat the conductive sampling swab to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab.

TECHNICAL FIELD

The disclosure relates to methods and systems for detection of a chemical sub stance.

BACKGROUND

Trace detection systems are designed to collect, analyze, and identify minute amounts, such as picograms or nanograms, of substances of interest that may otherwise be completely invisible to the unaided eye. Substances of interest to be detected by trace detection systems include explosives, drugs, chemical weapons, and toxic industrial chemicals. Traditionally, the trace particles are collected by an operator (e.g., a natural person) using a sampling swab. The operator swipes the suspected surface with a sampling swab and inserts the sampling swab into a thermal desorber. The thermal desorber heats the sampling swab by convective heating to evaporate the particles collected on this swab. The released vapors are ionized and subsequently analyzed. Ion Mobility Spectrometry (IMS) and Mass Spectrometry (MS) trace detectors are commonly used methods to detect explosive, narcotics, and chemical weapon threats with high sensitivity and rapid analysis capabilities.

SUMMARY

In some examples, this disclosure describes systems and techniques for trace detection of low volatility substances or materials. The systems and techniques described utilize heating to desorb and vaporize low volatility substances captured by an impermeable conductive sampling swab.

In one example, this disclosure describes a system including: a conductive sampling swab comprising a non-mesh substrate; and a thermal desorber comprising a clamping assembly configured to releasably hold the conductive sampling swab, wherein the clamping assembly is configured to be electrically connected to a voltage or current source, wherein the thermal desorber is configured to resistively heat the conductive sampling swab to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab.

In another example, this disclosure describes a method including: inserting a conductive sampling swab into a thermal desorber, wherein the conductive sampling swab comprises a non-mesh substrate; clamping, via a clamping assembly of the thermal desorber, the conductive sampling swab, wherein the clamping assembly is configured to be electrically connected to a voltage or current source; and resistively heating the conductive sampling swab, via a current applied through the conductive sampling swab, to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab.

In another example, this disclosure describes a trace detection system including: a conductive sampling swab; a thermal desorber includes a clamping assembly configured to releasably hold the conductive sampling swab, wherein the clamping assembly is configured to be electrically connected to a voltage or current source and the conductive sampling swab, wherein the clamping assembly is configured to contact the conductive sampling swab with a substantially even pressure over a first area at a first position on the conductive swab and with a substantially even pressure over a second area at a second position on the conductive swab and conduct a voltage or current to the conductive sampling swab via the first and second areas while holding the conductive sampling swab; the voltage or current source; a trace detector configured to determine at least one of a presence or a composition of a vaporized sample material, wherein the thermal desorber is configured to resistively heat a sample material disposed on the conductive sampling swab to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab by applying a current through the conductive sampling swab, wherein the trace detector is fluidically coupled to the thermal desorber and is configured to receive vaporized sample material.

In another example, this disclosure describes a conductive sampling swab including: a non-mesh substrate, wherein the conductive sampling swab is configured to be replaceably clamped by a clamping assembly of a thermal desorber, wherein the conductive sampling swab is configured to be resistively heated to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab via the application of a current through the conductive sampling swab by the thermal desorber.

In another example, this disclosure describes a thermal desorber including: a clamping assembly configured to releasably hold a conductive sampling swab, wherein the clamping assembly is configured to be electrically connected to a voltage or current source, wherein the clamping assembly is configured to be electrically connected to the conductive sampling swab, wherein the thermal desorber is configured to resistively heat the conductive sampling swab to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab.

DETAILED DESCRIPTION

In some examples, the disclosure describes systems and methods for trace detection of sample materials. In some examples, the systems and methods disclosed include a conductive sampling swab having an impermeable substrate, e.g., substantially gas, water, and/or air impermeable and/or non-transmissive to a gas, water, water vapor, moisture, air. For example, the conductive sampling swab may be continuous (e.g., non-mesh) such that gas, water or water vapor, or air may not pass or transmit through the thickness of the conductive sampling swab, e.g., within a period such as hours and/or days. The conductive swab may be configured to be heated via resistive heating to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab. In some examples, the conductive sampling swab is configured to be inserted into a thermal desorbing including a clamping assembly. The clamping assembly may be configured to releasably hold the conductive sampling swab and configured to be electrically connected to a voltage or current source. The clamping assembly may further be configured to be electrically connected to the conductive sampling swab.

The systems and methods of the present disclosure provide for improved detection of substances having a low volatility (e.g., explosives) through direct heating of an impermeable conductive sampling swab via an electric current passed through the conductive sampling swab.

Physically swiping surfaces is a common method for collecting sample materials that may be of security and/or forensic interest. The sampling swabs are typically porous allowing trace particles to be trapped within pores or to attach by other mechanical means. Fiber-based swabs may include natural fibrous materials such as muslin and cellulose and/or synthetic materials such as Nomex® and Teflon™-coated fiberglass. The porosity of a sampling swab may be designed to match the maximum dimensions of measured and/or simulated size distributions for particle sizes of common explosive and narcotic materials. However, the porosity or roughness of a sampling swab can cause abrasion of the sampled surface causing unintended surface (matrix) material to adhere to the sampling swab in addition to the sample material and potentially interfere with the detection of the sample material.

After the sample is collected, the swab is inserted into a thermal desorber and heated by convective heating to release the vapors of collected chemical substances. It is commonly accepted that slow heating rates are preferential for enhanced sensitivity, e.g., low or slow heating rates give clearer desorption separation between compounds with low vapor pressure versus high vapor pressure. Thermal desorbers may have a toaster-like design where the air gap between the flat heaters and sampling swab limits the heating rate and also serve as a conduit directing released vapors into a chemical analyzer.

Sampling swabs should be durable, free of impurities, and capable of withstanding high temperatures. The temperatures of the thermal desorber used for detection of explosive and narcotic samples may be limited to about 240 degrees Celsius (° C.) or to about 150° C., even though some compounds of interest, such as inorganic salts, may require temperatures of 700° C. or higher to efficiently desorb from the swab surface. For example, the thermal desorber may be limited by the power and time required to convectively heat the swab, or heat the swab via infrared radiation, inside a hot enclosure with limited heat transfer, e.g., through a volume of air in which the swab is positioned. Additionally, the swab itself may not be able to withstand temperatures significantly above 250° C.

Further, accumulation of moisture, e.g., water and/or water vapor, inside the pores of sampling swabs exposed to ambient conditions may degrade the performance of trace detectors. For example, water vapor loaded into an IMS trace detector along with the sample material may cause ion peak positions to be substantially shifted from their known positions.

Generally, trace detection systems and methods may focus on sample collection efficiency, e.g., to increase a detectable signal. However, methods for improvement of trace system sensitivity based on a cumulative response of a chemical substance may be impractical.

In accordance with the systems and methods disclosed herein, trace detection may focus on improving the signal-to-noise ratio of a chemical substance of interest within just a subset of consecutive scans. In some examples, the heating rate of a sampling swab may be increased, rather than decreased, to allow one or more substances of interest to be sampled over a shorter period of time and thereby increase a peak signal intensity of one or more of the substances of interest. In some examples, the increased heating rates are achieved via direct heating, e.g., resistive heating, of a conductive sampling swab.

In some examples, a conductive sampling swab comprises a non-mesh substrate, and optionally a coating disposed on a major surface of the substrate. In some examples, the conductive sampling swab may be a metal foil, e.g., the non-mesh substrate may comprise a metal foil. The conductive sampling swab may be a configured to retain a sample material, e.g., on a major surface of the conductive sampling swab such as a major surface of the non-mesh substrate or optionally a major surface of a coating disposed on the non-mesh substrate. The conductive sample swab may be configured to be repeatably clamped by a clamping assembly of a thermal desorber. The conductive sampling swab may be further configured to be resistively heated to a temperature sufficient to vaporize the sample material via the application of a current through the conductive sampling swab by the thermal desorber.

In some examples, the conductive sampling swab may be configured to be heated via flash heating. For example, the thermal desorber may cause a power source, e.g., a voltage or current source, to cause a current to flow through the sampling swab via the clamping assembly to flash heat the sampling swab to the temperature sufficient to vaporize the sample material with a relatively high heating rate, e.g., 50° C., and/or within in a relatively short period of time, e.g., within a few minutes or within a few seconds. For example, the conductive sampling swab may be durable and thin, e.g., with a low thermal mass allowing the mass to heat at the relatively high rate. The conductive sampling swab may also be configured to be heated to higher temperatures than conventional swabs, enabling desorption of involatile chemical compounds such as inorganic salts, e.g., to a temperature equal to or greater than 500° C., or 700° C., or higher. In some examples, the conductive sampling swab may be non-abrasive and non-porous, e.g., the conductive sampling swab may reduce collection of substrate materials on which the conductive sampling swab is swabbed, such as vinyl or plastics, via reduced abrasion with the substrate material while still collecting the sample material of interest. In other words, the conductive sampling swab may reduce and/or eliminate contamination, increase the signal-to-noise ratio, and reduce and/or eliminate false positives and/or false negatives in identification of the presence of a sample material of interest. In some examples, the conductive sampling swab may reduce and/or eliminate accumulation of water or moisture on or within the conductive sampling swab, allowing the sampling swab to be used and/or stored in a variety of environmental conditions (e.g., different ambient temperatures and/or humidity during storage and/or sample collection or swabbing).

FIG.1is a block diagram illustrating an example trace detection system100. In the example shown, system100includes conductive sampling swab110, thermal desorber102including clamping assembly104, electric current controller170, chemical analysis device180, data acquisition/control module190and computing device192. The example shown inFIG.1is representative of conductive sampling swab110clamped, via clamping assembly104, and in position to be heated. In some examples, conductive sampling swab110may be insertable and removable from clamping assembly104, e.g., to allow for sample collection or swabbing (e.g., a surface) with conductive sampling swab110.

Conductive sampling swab110may be configured to be used by an operator to physically swipe a surface of interest and collect an amount of a sample material on a surface of conductive sampling swab110, e.g., such that the amount of sample material is disposed on conductive sampling swab110. Conductive sampling swab110may be configured to be held by the operator by hand (e.g., with or without gloves) or by an extended sample holder or wand, or by any other suitable means. Conductive sampling swab110may be configured to be placed in thermal desorber102, e.g., by hand or by the extended sample holder or wand, or by any suitable means. For example, the operator may place conductive sampling swab110inside enclosure160after swiping sampling swab110to collect an amount of a sample material.

In some examples, conductive sampling swab110may include a non-mesh substrate, e.g., a substrate that is not a knit, woven, or knotted material of open texture. The non-mesh substrate may comprise a metal or metal alloy. For example, conductive sampling swab110may include a metal foil formed of, e.g., a carbon steel such as 1095 carbon steel, a spring steel, or any suitable metal. In some examples, conductive sampling swab110may be substantially elastic, that is, conductive sampling swab110may resume its normal shape after being stretched or compressed. For example, conductive sampling swab110may be configured to be bent, stretched, or otherwise deformed, e.g., to at least partially conform to the shape of a surface that an operator is swiping with conductive sampling swab110, and return to its original size and/or shape after being bent, stretched, or deformed. In some examples, conductive sampling swab110may have a Young's modulus greater than or equal to 9,000 kilopounds per square inch (ksi) and/or a resistivity greater than or equal to 50 micro Ohm-centimeters (μΩ-cm).

In some examples, conductive sampling swab110may be configured to be resistively heated, e.g., via direct heating, joule heating, or the like, to a temperature sufficient to vaporize the sample material disposed on conductive sampling swab110. For example, conductive sampling swab110may be configured to withstand being heated to temperatures equal to or greater than 500° C., or 700° C., without vaporizing material comprising conductive sampling swab110, e.g., without vaporizing the non-mesh substrate, coating, and/or any other layers or materials comprising conductive sampling swab110, e.g., such as intermediate coatings and/or binder or primer layers.

Thermal desorber102is configured to hold and resistively heat conductive sampling swab110. For example, thermal desorber102may include clamping assembly104. Clamping assembly104is configured to releasably hold conductive sampling swab110. In some examples, clamping assembly104is configured to be electrically connected to a voltage or current source, e.g., electric current controller170. In some examples, clamping assembly104may be configured to be electrically connect to conductive sampling swab110, e.g., with a substantially even pressure and/or electrical contact within one or more areas of contact. For example, clamping assembly104may be used for resistively heating, as well as clamping, conductive sampling swab110. In other examples, the resistive heating may be performed by components other than those used to clamp the swab, e.g., clamping assembly104may clamp conductive sampling swab110while a separate electrical connector may be used to resistively heat conductive sampling swab110.

In some examples, clamping assembly104is configured to conduct an electrical current through conductive sampling swab110via one or more contact areas and substantially evenly within those contact areas, e.g., to avoid spatial “spikes” in charge density at contact points between clamping assembly104and conductive sampling swab110that may burn, degrade, ablate, or otherwise locally degrade the material of conductive sampling swab110due to a large local current and/or charge density. In other words, at contact positions between clamping assembly104and conductive sampling swab110, the clamping assembly104is configured to spread the charge density over an area substantially evenly. In some examples, clamping assembly104is configured to contact conductive sampling swab110with a substantially even pressure over a first area at a first position on conductive swab110and with a substantially even pressure over a second area at a second position on conductive swab110and conduct a voltage or current to conductive sampling swab110via the first and second areas while holding conductive sampling swab110. In other words, clamping assembly104may be an electrical connection apparatus between electric current controller170and conductive sampling swab110configured to mechanically hold conductive sampling swab110without damaging conductive sampling swab110and electrically connect sampling swab110such that electric current controller170may provide a relatively large current to conductive sampling swab110to heat conductive sampling swab110without localized damage (e.g., burning, ablating, and the like) to conductive sampling swab110at the electrical contact positions. In some examples, clamping assembly104may be substantially similar to clamping assembly200illustrated and described below with reference toFIG.2.

In the example shown, clamping assembly104is disposed within enclosure160. Enclosure160may include a sample opening, or aperture, through which an operator may insert or remove conductive sampling swab110into clamping assembly104. In the example shown, clamping assembly104includes clamps120,130,140, and150. Clamps120and140are stationary, and clamps130and150are configured to move relative to stationary clamps120,140, e.g., towards and away from stationary clamps120,140in the directions indicated by the arrows inFIG.1. In other examples, clamps130,150may be stationary and clamps120,140may be configured to move relative to clamps130,150, and in other examples all of clamps120,130,140, and150may be configured to move relative to each other.

In the example shown, stationary clamp120and movable clamp130are configured to clamp (e.g., releasably hold) conductive sampling swab110at a first position, e.g., a front position which may be closer to a front edge of conductive sampling swab110, with front being defined relative to the sample opening of enclosure160. Clamps120,130may clamp conductive sampling swab110by contacting conductive sampling swab110substantially evenly across a first bottom side area on a first major surface of conductive sampling swab110by stationary clamp120and by contacting conductive sampling swab110substantially evenly across a first top side area on a second major surface of conductive sampling swab110by movable clamp130. Similarly, in the example shown, stationary clamp140and movable clamp150are configured to clamp (e.g., releasably hold) conductive sampling swab110at a second position, e.g., a back position which may be farther to a front edge of conductive sampling swab110relative to the sample opening of enclosure160. Clamps140,150may clamp conductive sampling swab110by contacting conductive sampling swab110substantially evenly across a second bottom side area on a first major surface of conductive sampling swab110by stationary clamp140and by contacting conductive sampling swab110substantially evenly across a second top side area on a second major surface of conductive sampling swab110by movable clamp150. Clamps120,130,140,150may define the location, size, and shape of the contact areas, e.g., clamp120defining first bottom side area, clamp130defining first top side area, clamp140defining second bottom side area, and clamp150defining second top side area. In the example shown, “top” and “bottom” are relative to a vapor collection assembly162included thermal desorber102, e.g., within enclosure160, with “top” being closer to vapor collection assembly162and “bottom” being opposite top from vapor collection assembly162.

In some examples, clamps120,130,140, and150may conform to the surface shapes of the respective major surfaces of conductive sampling swab110, or conductive sampling swab110may be configured such that its major surfaces conform to the surface shape of the contact surfaces of clamps120,130,140, and150, e.g., so as to apply substantially even pressure and to make a substantially even electrical connection over the surface areas in contact between clamps120,130,140, and150and the major surfaces of conductive sampling swab110.

For example, conductive sampling swab110may have substantially flat major (e.g., top and bottom) surfaces, and the contacting surfaces of clamps120,130,140, and150may have substantially flat contacting surfaces. In some examples, clamps120,130,140, and150may be configured to releasably hold conductive sampling swab110in a substantially coplanar orientation, e.g., clamps120and140are substantially coplanar such that when movable clamps130,150press against the top surface of conductive sampling swab110the conductive sampling swab110is held substantially without being bent, twisted, or otherwise deformed. Additionally, clamps120,130,140, and150may be configured to releasably hold conductive sampling swab110with flat top and bottom with substantially even contact over the respective contact areas, e.g., without an angle between the planes defined by the contacting surfaces of clamps120,130,140, and150and the top and bottom surfaces of conductive sampling swab110. In some examples, the moving clamps may be on opposite sides of conductive sampling swab110, e.g., clamps120and150may be moving, and clamps130and140may be stationary, or vice versa. In some examples, there may be only one set of clamps, e.g., clamps120,130. In some examples, there may be only one clamp, e.g.,120, which may be a moving clamp configured to hold conductive sampling swab110against a stationary backing material.

In some examples, the contacting surfaces of clamps120,130,140, and150may have a sharp or serrated edge. For example, the sharp or serrated edge may be configured to press into a substrate or a coating (e.g., substrate302and/or coating304described below atFIG.3) to hold and electrically connect to conductive sampling swab110.

In the example shown, clamping assembly104is configured to be electrically connected to a voltage or current source, e.g., electrical current source170via electrical connectors172,174. In the example shown, clamps120and140are electrically connected to electrical current source170. Generally, any of clamps120,130,140, or150may be electrically connected to electrical current source170. In some examples, none of clamps120,130,140, and150are connected to electrical current source170, and clamping assembly104includes electrical connectors172,174which may be configured to electrically connect conductive sampling swab110to electrical current source170.

In some examples, the operator may insert conductive sampling swab110into enclosure160and manually operate clamping assembly104to clamp conductive sampling swab110. In some examples, clamping by clamping assembly104may be initiated by data acquisition/control module190, computing device192, or any other suitable device, e.g., in response to a proximity sensor indicating the presence of conductive sampling swab110or in response to an action by the operator such as pushing a button or a user interface object of data acquisition/control module190, computing device192, or any other suitable device configured to cause clamping assembly102to clamp and/or unclamp.

In the example shown, enclosure160may be sealed (fully or partially) to prevent surrounding air and/or contaminants from entering chemical analysis device180, e.g., via vapor collection assembly162and/or vapor conduit164. Enclosure160may be heated to avoid condensation of vapors of chemical substances inside enclosure160.

Thermal desorber102includes vapor collection assembly162, which may be configured to collect vapor112including vaporized sample material that has been vaporized from conductive sampling swab110. Vapor collection assembly162may be fluidically connected to vapor conduit164, both of which may be fluidically coupled to chemical analysis device180and configured to cause vapor to flow to chemical analysis device180, e.g., via a fan. In some examples, any or all vapor collection assembly162, vapor conduit164, or chemical analysis device180may be configured to ionize vapor112.

In some examples, thermal desorber102may be configured to flash heat conductive sampling swab110to a temperature sufficient to vaporize the sample material disposed on the conductive sampling swab100, e.g., in a few seconds or less. In some examples, the flash heating may comprise heating conductive sampling swab110, e.g., via resistive heating, to the temperature in, or five seconds or less, or two seconds or less. In some examples, the temperature sufficient to vaporize the sample material disposed on the conductive sampling swab may be greater than or equal to 500° C., or 700° C. In some examples, the sample material may comprise at least one of an explosive, a narcotic, a chemical warfare agent, a pesticide, a toxic industrial chemical, or a pharmaceutical trace contaminant. In some examples, the sample material may comprise at least one of sodium nitrate, potassium nitrate, strontium nitrate, barium nitrate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, sodium permanganate, or potassium permanganate. Thermal desorber102may be configured to vaporize any of the above mentioned sample materials, e.g., heat conductive sampling swab110to a temperature sufficient to vaporize any of the above sample materials.

Chemical analysis device180may be a trace-detector configured to determine any or all of the presence of vaporized sample material, a composition of sample material, an amount of the sample material, and/or an amount of each component of the composition of the sample material. In some examples, chemical analysis device180may be an ion mobility spectrometer, a semiconductor gas sensor, a Raman spectrometer, a mass spectrometer, a gas chromatograph, a chemiluminescence-based detector, an electrochemical sensor, an infrared spectrometer, or any suitable trace-detector or any combination thereof.

Computing device192may include a processor and/or processing circuitry and memory, and may be configured to control trace detection system100and/or any of its components, e.g., thermal desorber102, clamping assembly104, electric current controller170, chemical analysis device180, data acquisition/control module190, and/or any other hardware of trace detection system100, e.g., motors to move clamps130,150, a pump to move vapor112to chemical analysis device180, and the like. In some examples, computing device192may be substantially similar to computing device28further illustrated and described below with reference toFIG.9.

In some examples, data acquisition/control module190may be configured to control trace detection system100and/or any of its components, e.g., based on instructions from processing circuitry of computing device192. In some examples, processing circuitry and/or memory of computing device192may be configured to receive data from data acquisition/control module190and/or chemical analysis device180, and processing circuitry of computing device192may be configured to determine any of the presence of vaporized sample material, a composition of sample material, an amount of the sample material, and/or an amount of each component of the composition of the sample material.

FIG.2is a schematic illustration of an example clamping assembly200and conductive sampling swab210. Conductive sampling swab210may be substantially similar to conductive sampling swab110ofFIG.1and/or conductive sampling swab210illustrated and described below with reference toFIG.3. Clamping assembly200may be substantially similar to clamping assembly102ofFIG.1.

In the example shown, clamping assembly200includes conductive sampling swab210, four separate enclosure sections220,230,240,250, clamps260and270, solenoid actuators280and282and transfer line290fluidically connecting enclosure sections220,230,240,250with a chemical detection device, e.g., chemical analysis device180ofFIG.1.

Clamp260is located within enclosure section220and is driven by solenoid actuator280. Clamp270is located within enclosure section240and is driven by solenoid actuator282. In other examples, stepper motors may be used instead of solenoid actuators. In some examples, clamps260,270may be actuated manually by non-electric mechanical means (for example using lever connectors).

In the example shown, stationary clamps may be integrated within enclosure sections230and250. Front enclosure sections220and230are connected to electrical ground. Back enclosure sections250and240are normally connected to ground electrical ground, except when heating. Clamping assembly200may include one or more detectors, e.g., optical sensors, configured to determine when conductive sampling swab210is fully inserted and ready to be clamped. A control module may be configured to activate solenoid actuators280and282, e.g., based on a determination that conductive sampling swab210is fully inserted into clamping assembly200and is ready to be clamped, causing clamps260,270to move to clamp conductive sampling swab210at two locations and/or positions. The control module may be configured to deactivate solenoid actuators280and282, causing clamps260,270to move to release conductive sampling swab210.

In the example shown, back enclosure section250may be configured to be electrically connected to a voltage or current source, and electrically connected to conductive sampling swab210when in a clamped position. Back enclosure section250may be configured to apply a relatively low voltage or conduct a relatively low voltage supplied by the voltage/current source, to conductive sampling swab210and cause an electric current to flow through conductive sampling swab210. In some examples, the voltage applied to conductive sampling swab210may be 3 volts or less, and the electrical current may be a direct current (DC) ranging from 10 amperes (A) to 50 A. In some examples, conductive sampling swab210may have a relatively low conductance, e.g., conductive sampling swab210may comprise stainless steel, and thereby conduct the desired current at the desired voltage at voltage/current ranges that may be within the ranges of commercially available electrical power supplies. When assembled, enclosure sections220,230,240,250may form at least a partially sealed enclosure, where background air may enter only through the front slit substantially near conductive sampling swab210. In some examples, enclosure sections220,230,240,250may be configured to reduce and/or eliminate vapor condensation, e.g., enclosure sections220,230,240,250may be heated. In some examples, enclosure sections220,230,240,250may be heated by a flat ceramic heater (not shown inFIG.2). Transfer line290may be heated by a flexible Kapton heater (also not shown inFIG.2). In some examples, enclosure sections220,230,240,250may be controlled, e.g., via the controller, to be at a temperature of about 150° C., and transfer line290may be controlled to be at a temperature of about 180° C.

FIG.3is a cross-sectional view of an example conductive sampling swab210, the cross-section being taken along line A ofFIG.2. Conductive sampling swab210includes substrate302, coating304, and surface306. In some examples, conductive sampling swab210includes additional layers, e.g., a primer or binder layer (not shown) between substrate302and coating304configured to increase and/or improve adhesive of coating304to substrate302. In some examples, conductive sampling swab210may not include coating304, and surface306may be a surface of substrate302rather than coating304.

In some examples, substrate302may be conductive, and in other examples substrate302may be substantially non-conductive and coating304may be conductive. For example, substrate302may comprise a non-conductive material such as a fiberglass, Nomex®, or any other suitable non-conductive material, and coating304may be conductive. In some examples, substrate302may comprise a composite material, e.g., conductive, non-conductive, or a composite of both conductive and non-conductive materials.

Substrate302may be substantially non-absorbent. For example, substrate302may be a solid material, or a porous material sealed by coating304, and substrate302may be configured to not trap and/or absorb fluids, such as water.

In some examples, substrate302may be substantially impermeable, e.g., substantially gas, water, and/or air impermeable and/or substantially non-transmissive to a gas, water, water vapor, moisture, and/or air. In some examples, substrate302may have a water vapor transmission rate (WVTR) of less than or equal to 0.01 grams per meter squared per day (g/(m2*day)) For example, the conductive sampling swab may be continuous such that gas, water or water vapor, or air may not pass or transmit through the thickness of the conductive sampling swab, at least within a substantial period of time such as hours and/or days.

Substrate302may be a metal or metal alloy substrate, such as a metal foil, and may be configured to retain a sample material, e.g., any of, but not limited to, the sample materials described herein. In some examples, the metal foil may be a carbon steel, such as 1095 carbon steel, a spring steel, or any suitable metal or alloy or combination thereof. In some examples, substrate302may comprise a plurality of fibers and a filler or binder material, e.g., filling fiber gaps.

Substrate302may have any thickness suitable for using conductive sampling swab210, e.g., a thickness enabling conductive sampling swab210to be handled, used as a swab, and resistively heated to the temperature sufficient to vaporize a sample material. In some examples, substrate302may have a thickness greater than or equal to about 10 micrometers and less than or equal to about 130 micrometers thick.

Coating304may be a graphite coating, a graphene coating, or any suitable coating or combination thereof. In some examples, coating304may be electrically conductive, e.g., coating304may include conductive material and/or a metal. In other examples, coating304may be non-conductive, e.g., and substrate302may be conductive. In some examples where coating304is non-conductive, coating304may include uncoated areas or areas with conductive material, e.g., to provide an electrical connection from surface306to substrate304.

In the example shown, coating304is disposed on one major surface of substrate302. In some examples, conductive sampling swab210may include a coating304on both major surfaces of substrate302(e.g., on both sides of substrate302), and may further include any associated primer/binder layers between substrate302and either coating304, and the coatings304on both sides of substrate302may be the same as each other, or may be different from each other, and may be any of the coatings304described herein.

In some examples, coating304may be substantially non-absorbent. In some examples, coating304and may be configured to seal substrate302, e.g., coating304may be substantially impermeable to a gas or fluid, such as air, water, and/or water vapor.

Surface306may be configured to pick up and/or capturing sample material. In some examples, surface306may be configured to be substantially smooth and/or planar. In other examples, surface306may be configured to have a surface roughness. For example, surface306may have a surface arithmetic roughness average (Ra) of greater than or equal to 0.1 micrometers, greater than or equal to 0.2 micrometers, greater than or equal to 0.25 micrometers, greater than or equal to 0.45 micrometers, or greater than or equal to 0.6 micrometers. In some examples, surface306may have a surface roughness from being abraded with an abrasive, e.g.,240grit sandpaper. In some examples, the sample material may be at least one of an explosive, a narcotic, a chemical warfare agent, a pesticide, a toxic industrial chemical, or a pharmaceutical trace contaminant, or at least one of sodium nitrate, potassium nitrate, strontium nitrate, barium nitrate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, sodium permanganate, or potassium permanganate.

Conductive sampling swab210may be configured to be resistively heated to a temperature sufficient to vaporize the sample material, e.g., via the application of a current through one or both of substrate302and coating304by a thermal desorber, e.g., thermal desorber102(FIG.1). In some examples, the temperature sufficient to vaporize the sample material is greater than or equal to 500° C., or greater than or equal to 700° C.

Conductive sampling swab210may configured to be removably clamped by a clamping assembly of a thermal desorber. For example, conductive sampling swab210may be configured to be inserted, clamped, heated, and removed from the clamping assembly, and conductive sampling swab210may be configured to be reused.

Conductive sampling swab210may be substantially elastic, that is, substrate302and coating304may resume their normal shape after being stretched or compressed. For example, conductive sampling swab210may be configured to be bent, stretched, or otherwise deformed, e.g., to at least partially conform to the shape of a surface that an operator is swiping with conductive sampling swab210, and return to its original size and/or shape after being bent, stretched, or deformed. In some examples, conductive sampling swab210, or either of substrate302or coating304, may have a Young's modulus greater than or equal to 9,000 kilopounds per square inch (ksi) and/or a resistivity greater than or equal to 50 micro Ohm-centimeters (μΩ-cm).

FIG.4is a plot of an example ion mobility plasmagram of a TNT sample. In the example shown, plot400may be an ion mobility plasmagram of an ion mobility-based trace detector operating in a negative mode. In the example shown, 1 microliter of TNT solution (1 nanogram/microliter in methanol) was directly deposited on conductive sampling swab210and dried out. The conductive sampling swab210was made of 304 stainless steel foil having a 0.001 inch thickness. Plasmagram400illustrates a high signal-to-noise ratio for TNT ion peak202with a low (e.g., “clean”) chemical background, indicating that conductive sampling swab210has a reduced, or zero, accumulation of environmental contaminants, including water. In the example shown, conductive sampling swab210has improved (e.g., less) accumulation of environmental contaminants and water as compared with a fiberglass or a Nomex® sampling swab.

FIG.5Ais a plot of an example ion mobility plasmagram500of a collected potassium chlorate (KClO3) sample using ion mobility-based trace detector operating in a negative mode.FIG.5Bis a plot of an example desorption profile550of a collected KClO3 sample.FIG.6Ais a plot of an example ion mobility plasmagram600of a collected KClO4 sample using an ion mobility-based trace detector operating in a negative mode.FIG.6Bis a plot of an example desorption profile650of a collected KClO4 sample.FIGS.5A,5B,6A, and6Bare described concurrently below.

Inorganic salts represent a class of substances with vapor pressure much lower than a vast majority of explosive or narcotics substances. At the same time, there is a pressing need to detect these substances at trace levels together with other substances of interest using the same detection system. Potassium chlorate (KClO3) and potassium perchlorate (KClO4) represent practical examples of low volatility samples and are inorganic salts with melting points of 356° C. and 525° C., respectively.

In the examples shown, nanograms level solutions of KClO3 and KClO4 salts in water were directly deposited on a conductive sampling swab210. Conductive sampling swab210was made of 304 stainless steel foil having a 0.001 inch thickness. The solutions were then dried out. Conductive sampling swab210was then rapidly heated, e.g., via thermal desorber102ofFIG.1, with a DC electric current of approximately 25 amperes for 8 seconds of heating duration. Conductive sampling swab210reached a temperature of approximately 700° C. Desorption profiles550and650may indicate an amount of desorption of a sample material from conductive sampling swab210. In the example shown inFIGS.5B, about 100% of the KClO3 sample deposited on conductive sampling swab210was desorbed from the surface of conductive sampling swab210within 8 seconds of direct (e.g., resistive) heating of conductive sampling swab210. In the example shown inFIG.6B, about 80% of the KClO4 sample deposited on conductive sampling swab210(e.g., a different conductive sampling swab210or the same conductive sampling swab210after cleaning) was desorbed from the surface of conductive sampling swab210within 8 seconds of direct (e.g., resistive) heating of conductive sampling swab210.

FIG.7is a plot of an example heating temperature profile700for a conductive sampling swab. In some examples, a thermal desorber may be configured to cause a conductive sampling swab to have temperature profile700, e.g., via resistive heating. For example, conductive sampling swab210may be inserted into thermal desorber102and clamped by clamping assembly104or clamping assembly200. Computing device192(or computing device28described below) may be configured to cause data acquisition/control module190to activate electric current controller170to provide a current through conductive sampling swab210according to a pre-programmed time profile and/or pattern, e.g., to heat conductive sampling swab over a period of time to the temperature profile700. For example, the temperature of conductive sampling swab210may be directly proportional to the current applied to conductive sampling swab210by current controller170.

In some examples, computing device192may be configured enhance the sensitivity of chemical analysis device180toward one or more samples of interest, or certain groups of substances of interest. In the example shown, temperature profile700increases to a first temperature T1within an amount of time between zero seconds and time s1, e.g., for an amount of time s1. The temperature remains substantially constant at T1, e.g., the temperature “plateaus” at a first plateau for an amount of time between times s1and s2. The temperature then increases to a second, higher temperature T2between times s2and s3, e.g., for an amount of time s3−s2, and remains relatively constant at a second plateau at T2between times t3and t4, e.g., for an amount of time t4−t3. Computing device192may be configured enhance the sensitivity of chemical analysis device180by causing the temperature of conductive sampling swab210to follow temperature profile700, and a first sample of interest may desorb at the first temperature T1between times s1and s2for analysis by chemical analysis device180. A second sample of interest may have a higher desorption temperature, and may not desorb from conductive sampling swab210between times s1and s2. The second sample of interest may instead desorb at higher temperature T2between times s3and s4for analysis by chemical analysis device180. The time between s1and s2may be such that all of the first sample is desorbed between times s1and s2, and only the second sample of interest is desorbed between times s3and s4.

In other examples, computing device192may be configured to cause data acquisition/control module190to activate electric current controller170to provide a current through conductive sampling swab210to achieve a different temperature profile700of conductive sampling swab210, or any suitable temperature profile700of conductive sampling swab210. For example, computing device192may cause conductive sampling swab210to have a temperature profile700with more or fewer plateaus, temperature ramp ups and ramp downs with any suitable shape, e.g., linear, quadratic, any higher order polynomial shape, exponential, or any more or less complex temperature profile shape. For example, computing device192may be preprogrammed to cause both the current and/or voltage to be applied to conductive sampling swab210to have any suitable temperature profile700to enhance the sensitivity of chemical analysis device180toward one or more samples of interest.

FIG.8is a flow diagram of an example method800of detecting a trace amount of a low volatility sample material. AlthoughFIG.8is discussed using trace detection system100ofFIG.1, computing device28ofFIG.9, and conductive sampling swab210ofFIG.3, is to be understood that the methods discussed herein may include and/or utilize other systems and methods in other examples.

An operator (e.g., a user, a person) may collect a sample of a material and/or substance of interest by swiping a surface of interest with conductive sampling swab210(802). The operator may insert conductive sampling swab210thermal desorber102(804). Conductive sampling swab210may comprise a impermeable substrate, e.g., substrate302.

Computing device28(e.g., processors30or processing circuitry) may cause clamping assembly104to clamp conductive sample210at two locations or positions to provide an electrical connection to a source of electrical current, e.g., electric current controller170(806). For example, a detector (e.g., an optical detector) may sense the position of conductive sampling swab210during insertion step (804), and computing device28may determine that the conductive sampling swab210is in a positioned to be clamped and may cause motors, solenoids, stepper motors or the like to move one or more clamps to clamp and hold the conductive sampling swab210. In some examples, computing device28may indicate to the operator, e.g., via UI devices32, to manually move one or more clamps to clamp and hold the conductive sampling swab210, e.g., via a lever or other mechanism. In some examples, the operator may indicate to computing device28, e.g., via UI devices32, to move one or more clamps to clamp and hold the conductive sampling swab210, e.g., via pressing a button or using a UI device32. In some examples, clamping step (806) may be performed solely by the operator, e.g., the operator may be able to see when conductive sampling swab210is in position to be clamped and may manually clamp conductive sampling swab210with one or more clamps via a mechanism and without an action by computing device28. Clamping assembly104, e.g., the one or more clamps, may be configured to be electrically connected to electric current controller170, and the one or more clamps may be conductive and configured to be electrically connected to conductive sampling swab210to provide an electrical connection between electric current controller170and conductive sampling swab210to allow a current to flow through conductive sampling swab210.

Computing device28may cause electric current controller170to heat conductive sampling swab210via applying an electric current through conductive sampling swab210(808). For example, computing device28may cause data acquisition/control module190to activate electric current controller170to provide a current through conductive sampling swab210. Electric current controller170may then apply a voltage between front and back clamps of clamping assembly104to pass electric current through conductive sampling swab210. In some examples, the front clamp may be connected to ground to ensure safety of operation, while the back clamp may be connected to an electric potential above or below ground. The electric current may be constant or varied in time. Computing device28may control, in real time, the intensity of the electric current and duration of a desorption interval or period, or the intensity of the electric current and duration of a desorption interval or period may be pre-programmed at a hardware level. The electric current may be either direct current (DC) or alternating current (AC). In some examples, electric current controller170may provide the electric current in a pulsed fashion (for example, using pulse-width and/or pulse-frequency modulation).

Computing device28may cause electric current controller170to resistively heat conductive sampling swab210to a temperature sufficient to cause full or partial vaporization of the sample material disposed on conductive sampling swab210, e.g., to a temperature greater than or equal to 500° C., or 700° C. Vapor collection assembly162and vapor conduit164may then transport the generated vapors of the sample material to a trace detection system, e.g., chemical analysis device180. In some examples, computing device28may cause current controller170to heat conductive sampling swab210repeatedly, e.g., according to a set of time intervals. In some examples, each time interval may have a different electric current and duration. In some examples, computing device28may cause current controller170to heat conductive sampling swab210with a varied time duration and varied current amount, e.g., a varied time and current amount specific to vaporize a specific sample material and/or chemical substance. In some examples, computing device28may cause current controller170to flash heat conductive sampling swab210to the temperature sufficient to vaporize the sample material disposed on the conductive sampling swab, e.g., in eight seconds or less, or in five seconds or less, or in two seconds or less. In some examples, computing device28may cause current controller170to heat conductive sampling swab210according to a temperature profile, e.g., temperature profile700ofFIG.7.

Computing device28may cause chemical analysis device180to analyze the sample vapors (810). In some examples, analysis at (810) may occur at least partially simultaneously with heating at (808).

Computing device28may identify the sample material (812). For example, trace detection control unit20may receive analysis data from chemical analysis device180and may determine the presence of vaporized sample material, a composition of the sample material, an amount of the sample material, and/or an amount of each component of the composition of the sample material.

In some examples, method800may be used to identify a sample material comprising at least one of an explosive, a narcotic, a chemical warfare agent, a pesticide, a toxic industrial chemical, or a pharmaceutical trace contaminant. In some examples, method800may be used to identify a sample material comprising at least one of sodium nitrate, potassium nitrate, strontium nitrate, barium nitrate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, sodium permanganate, or potassium permanganate.

FIG.9is a block diagram illustrating an example computing device28configured to control a trace detection system. In some examples, computing device28may be substantially similar to computing device190ofFIG.1.

As shown in the example ofFIG.9, computing device28includes one or more processors30, one or more user interface (UI) devices32, one or more communication units34, and one or more memory units36. Memory36of computing device28includes operating system38, UI module40, telemetry module42, and authentication unit20, which are executable by processors30. Each of the components, units or modules of computing device28are coupled (physically, communicatively, and/or operatively) using communication channels for inter-component communications. In some examples, the communication channels may include a system bus, a network connection, an inter-process communication data structure, or any other method for communicating data.

Processors30, in one example, may comprise one or more processors that are configured to implement functionality and/or process instructions for execution within computing device28. For example, processors30may be capable of processing instructions stored by memory36. Processors30may include, for example, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate array (FPGAs), or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing devices or circuitry.

Memory36may be configured to store information within computing device28during operation. Memory36may include a computer-readable storage medium or computer-readable storage device. In some examples, memory36include one or more of a short-term memory or a long-term memory. Memory36may include, for example, random access memories (RAM), dynamic random access memories (DRAM), static random access memories (SRAM), magnetic discs, optical discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable memories (EEPROM). In some examples, memory36is used to store program instructions for execution by processors30. Memory36may be used by software or applications running on computing device28(e.g., authentication unit20) to temporarily store information during program execution.

Computing device28may utilize communication units34to communicate with external devices via one or more networks or via wireless signals. Communication units34may be network interfaces, such as Ethernet interfaces, optical transceivers, radio frequency (RF) transceivers, or any other type of devices that can send and receive information. Other examples of interfaces may include Wi-Fi, NFC, or Bluetooth radios. In some examples, computing device28utilizes communication units34to wirelessly communicate with an external device, such as electric current controller170, chemical analysis device180, and data acquisition/control module190fromFIG.1.

UI devices32may be configured to operate as both input devices and output devices. For example, UI devices32may be configured to receive tactile, audio, or visual input from a user of computing device28. In addition to receiving input from a user, UI devices32may be configured to provide output to a user using tactile, audio, or video stimuli. In one example, UI devices32may be configured to output content such as a GUI for display at a display device. UI devices32may include a presence-sensitive display that displays a GUI and receives input from a user using capacitive, inductive, and/or optical detection at or near the presence sensitive display.

Other examples of UI devices32include a mouse, a keyboard, a voice responsive system, video camera, microphone or any other type of device for detecting a command from a user, or a sound card, a video graphics adapter card, or any other type of device for converting a signal into an appropriate form understandable to humans or machines. Additional examples UI devices32include a speaker, a cathode ray tube (CRT) monitor, a liquid crystal display (LCD), organic light emitting diode (OLED), or any other type of device that can generate intelligible output to a user.

Operating system38controls the operation of components of computing device28. For example, operating system38, in one example, facilitates the communication of UI module40, telemetry module42, and trace detection control unit20with processors30, UI devices32, communication units34, and memory36. UI module40, telemetry module42, and trace detection control unit20may each include program instructions and/or data stored in memory36that are executable by processors30. For example, authentication unit20may include instructions that cause computing device28to perform one or more of the techniques described in this disclosure.

Computing device28may include additional components that, for clarity, are not shown inFIG.9. For example, computing device28may include a battery to provide power to the components of computing device28. Similarly, the components of computing device28shown inFIG.9may not be necessary in every example of computing device28.

In the example illustrated inFIG.9, trace detection control unit20may be configured to control trace detection system100and/or any of its components, e.g., thermal desorber102, clamping assembly104, electric current controller170, chemical analysis device180, data acquisition/control module190, and/or any other hardware of trace detection system100, e.g., motors to move clamps130,150, a fan to move vapor112to chemical analysis device180, and the like. In some examples, trace detection control unit20may be configured to determine any of the presence of vaporized sample material, a composition of sample material, an amount of the sample material, and/or an amount of each component of the composition of the sample material, e.g., based on data received from data acquisition/control module190and/or chemical analysis device180telemetry module42. In some examples, trace detection control unit20may cause computing device and/or processors30to execute portions of method800described above.

This Disclosure Includes the Following Non-Limiting Examples.

Example 1: A system including: a conductive sampling swab comprising a non-mesh substrate; and a thermal desorber comprising a clamping assembly configured to releasably hold the conductive sampling swab, wherein the clamping assembly is configured to be electrically connected to a voltage or current source, wherein the thermal desorber is configured to resistively heat the conductive sampling swab to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab.

Example 2: The system of example 1, wherein the non-mesh substrate comprises a metal foil.

Example 3: The system of example 2, wherein the metal foil comprises at least one of 1095 carbon steel or a spring steel.

Example 4: The system of any one of examples 1 through 3, wherein the conductive sampling swab has a Young's modulus greater than or equal to 9,000 kilopounds per square inch (ksi), wherein the conductive sampling swab has a resistivity greater than or equal to 50 micro Ohm-centimeters (me-cm).

Example 5: The system of any one of examples 1 through 4, wherein the conductive sampling swab has a surface arithmetic roughness average (Ra) of greater than or equal to 0.25 micrometers.

Example 6: The system of example 5, wherein the conductive sampling swab comprises at least one of a graphite coating or a graphene coating disposed on the non-mesh substrate.

Example 7: The system of any one of examples 1 through 6, wherein the conductive sampling swab is configured to be reusable and replaceable within the clamping assembly.

Example 8: The system of any one of examples 1 through 7, wherein the clamping assembly is configured to be electrically connected to the conductive sampling swab.

Example 9: The system of example 8, wherein the clamping assembly is configured to contact the conductive sampling swab with a substantially even pressure over a first area at a first position on the conductive sampling swab and with a substantially even pressure over a second area at a second position on the conductive sampling swab.

Example 10: The system of any one of examples 1 through 9, wherein the temperature sufficient to vaporize the sample material disposed on the conductive sampling swab is greater than or equal to 500 degrees Celsius.

Example 11: The system of any one of examples 1 through 10, wherein the thermal desorber is configured to at least one of flash heat the conductive sampling swab or heat the conductive sampling swab according to a temperature profile.

Example 12: The system of any one of examples 1 through 11, wherein the sample material comprises at least one of an explosive, a narcotic, a chemical warfare agent, a pesticide, a toxic industrial chemical, or a pharmaceutical trace contaminant.

Example 13: The system of any one of examples 1 through 12, wherein the sample material comprises at least one of sodium nitrate, potassium nitrate, strontium nitrate, barium nitrate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, sodium permanganate, or potassium permanganate.

Example 14: A method including: inserting a conductive sampling swab into a thermal desorber, wherein the conductive sampling swab comprises a non-mesh substrate; clamping, via a clamping assembly of the thermal desorber, the conductive sampling swab, wherein the clamping assembly is configured to be electrically connected to a voltage or current source; and resistively heating the conductive sampling swab, via a current applied through the conductive sampling swab, to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab.

Example 15: The method of example 14, wherein the non-mesh substrate comprises a metal foil.

Example 16: The method of example 15, wherein the metal foil comprises at least one of 1095 carbon steel or a spring steel.

Example 17: The method of any one of examples 14 through 16, wherein the conductive sampling swab has a Young's modulus greater than or equal to 9,000 kilopounds per square inch (ksi), wherein the conductive sampling swab has a resistivity greater than or equal to 50 micro Ohm-centimeters (me-cm).

Example 18: The method of any one of examples 14 through 17, wherein the conductive sampling swab has a surface arithmetic roughness average (Ra) of greater than or equal to 0.25 micrometers.

Example 19: The method of example 18, wherein the conductive sampling swab comprises at least one of a graphite coating or a graphene coating on the non-mesh substrate.

Example 20: The method of any one of examples 14 through 19, wherein the conductive sampling swab is configured to be reusable and replaceable within the clamping assembly.

Example 21: The method of any one of examples 14 through 20, wherein the clamping assembly is configured to be electrically connected to the conductive sampling swab.

Example 22: The method of example 21, wherein the clamping assembly is configured to contact the conductive sampling swab with an even pressure over a first area at a first position on the conductive swab and with an even pressure over a second area at a second position on the conductive swab.

Example 23: The method of any one of examples 14 through 22, wherein the temperature sufficient to vaporize the sample material disposed on the conductive sampling swab is greater than or equal to 500 degrees Celsius.

Example 24: The method of any one of examples 14 through 23, wherein the thermal desorber is configured to at least one of flash heat the conductive sampling swab or heat the conductive sampling swab according to a temperature profile.

Example 25: The method of any one of examples 14 through 24, wherein the sample material comprises at least one of an explosive, a narcotic, a chemical warfare agent, a pesticide, a toxic industrial chemical, or a pharmaceutical trace contaminant.

Example 26: The method of any one of examples 14 through 25, wherein the sample material comprises at least one of sodium nitrate, potassium nitrate, strontium nitrate, barium nitrate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, sodium permanganate, or potassium permanganate.

Example 27: A trace detection system including: a conductive sampling swab; a thermal desorber includes a clamping assembly configured to releasably hold the conductive sampling swab, wherein the clamping assembly is configured to be electrically connected to a voltage or current source and the conductive sampling swab, wherein the clamping assembly is configured to contact the conductive sampling swab with a substantially even pressure over a first area at a first position on the conductive swab and with a substantially even pressure over a second area at a second position on the conductive swab and conduct a voltage or current to the conductive sampling swab via the first and second areas while holding the conductive sampling swab; the voltage or current source; a trace detector configured to determine at least one of a presence or a composition of a vaporized sample material, wherein the thermal desorber is configured to resistively heat a sample material disposed on the conductive sampling swab to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab by applying a current through the conductive sampling swab, wherein the trace detector is fluidically coupled to the thermal desorber and is configured to receive vaporized sample material.

Example 28: The trace-detection system of example 27, wherein the conductive sampling swab comprises a non-mesh metal foil comprising a carbon steel, wherein the conductive sampling swab has a Young's modulus greater than or equal to 9,000 kilopounds per square inch (ksi), wherein the conductive sampling swab has a resistivity greater than or equal to 50 micro Ohm-centimeters (me-cm).

Example 29: A conductive sampling swab including: a non-mesh substrate, wherein the conductive sampling swab is configured to be replaceably clamped by a clamping assembly of a thermal desorber, wherein the conductive sampling swab is configured to be resistively heated to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab via the application of a current through the conductive sampling swab by the thermal desorber.

Example 30: The conductive sampling swab of example 29, wherein the non-mesh substrate comprises a metal foil comprising at least one of 1095 carbon steel or a spring steel.

Example 31: The conductive sampling swab of example 29 or example 30 further configured to have a Young's modulus greater than or equal to 9,000 kilopounds per square inch (ksi) and a resistivity greater than or equal to 50 micro Ohm-centimeters (mΩ-cm).

Example 32: The conductive sampling swab of any one of examples 29 through 31 further configured to have a surface arithmetic roughness average (Ra) of greater than or equal to 0.25 micrometers.

Example 33: The conductive sampling swab of example 32 further comprising at least one of a graphite coating or a graphene coating on the non-mesh substrate.

Example 34: The conductive sampling swab of any one of examples 29 through 33, wherein the temperature sufficient to vaporize the sample material is greater than or equal to 500 degrees Celsius.

Example 35: The conductive sampling swab of any one of examples 29 through 34, wherein the sample material comprises at least one of an explosive, a narcotic, a chemical warfare agent, a pesticide, a toxic industrial chemical, or a pharmaceutical trace contaminant.

Example 36: The sampling swab of any one of examples 29 through 35, wherein the sample material comprises at least one of sodium nitrate, potassium nitrate, strontium nitrate, barium nitrate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, sodium permanganate, or potassium permanganate.

Example 37: A thermal desorber including: a clamping assembly configured to releasably hold a conductive sampling swab, wherein the clamping assembly is configured to be electrically connected to a voltage or current source, wherein the clamping assembly is configured to be electrically connected to the conductive sampling swab, wherein the thermal desorber is configured to resistively heat the conductive sampling swab to a temperature sufficient to vaporize a sample material disposed on the conductive sampling swab.

Example 38: The thermal desorber of example 37, wherein the clamping assembly is configured to contact the conductive sampling swab with an even pressure over a first area at a first position on the conductive swab and with an even pressure over a second area at a second position on the conductive sampling swab.

Example 39: The thermal desorber of example 37 or example 38, wherein the temperature sufficient to vaporize the sample material disposed on the conductive sampling swab is greater than or equal to 500 degrees Celsius.

Example 40: The thermal desorber of any one of examples 37 through 39, wherein the thermal desorber is configured to at least one of flash heat the conductive sampling swab or heat the conductive sampling swab according to a temperature profile.

Example 41: The thermal desorber of any one of examples 37 through 40, wherein the sample material comprises at least one of an explosive, a narcotic, a chemical warfare agent, a pesticide, a toxic industrial chemical, or a pharmaceutical trace contaminant.

Example 42: The thermal desorber of any one of examples 37 through 41, wherein the sample material comprises at least one of sodium nitrate, potassium nitrate, strontium nitrate, barium nitrate, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, sodium permanganate, or potassium permanganate.

Based upon the above discussion and illustrations, it is recognized that various modifications and changes may be made to the disclosed technology in a manner that does not necessarily require strict adherence to the examples and applications illustrated and described herein. Such modifications do not depart from the true spirit and scope of various aspects of the disclosure, including aspects set forth in the claims.