Jessica L. Staymates

Reliability of ion mobility spectrometry for qualitative analysis of complex, multicomponent illicit drug samples

Ion mobility spectrometry (IMS) has been used for trace analysis of illicit drugs, but it can also provide reliable qualitative analysis of bulk forensic drug items, despite the complexity of these samples. The drug/drug and drug/excipient combinations representing over 80% of the samples reported by state and federal forensic laboratories over the past 7 years were compiled from reports of the National Forensic Laboratory Information System (NFLIS). From this set of materials, IMS detection windows were set for eight controlled substances, including methamphetamine, 3,4-methylenedioxymethamphetamine hydrochloride (MDMA), cocaine, heroin, fentanyl, hydrocodone, oxycodone, and alprazolam. The reduced mobilities of the eight controlled substances were measured over an extended period of time to determine variability with respect to the size of the detection windows. Uncertainties in reduced mobilities smaller than 0.001 cm(2)V(-1)s(-1) were obtained, and detection windows were set to between ±0.003 and ±0.005 cm(2)V(-1)s(-1). Reduced mobilities are instrument and operating condition dependent, and must be determined for each instrument. Peak overlaps are observed in the drug/drug combinations, but at least one controlled substance can be detected in each mixture. Excipient concentrations must be quite high (>75 wt%) in binary mixtures to interfere with the detection of the controlled substance. IMS can be used to identify many of the excipients, and can detect multiple (for these samples, as many as 4) substances in complex samples. Over-the-counter (OTC) tablet medications for cold, flu, and allergy relief can be distinguished from tablets containing controlled substances. Bulk materials, including tablets, are sampled simply by using a fine probe to restrict the amount of material transferred to the IMS substrate. IMS represents a distinct advantage over color tests for field analysis of illicit drugs, except in the case of cannabis/THC samples.

Fabrication of adhesive coated swabs for improved swipe-based particle collection efficiency

Improving particle collection efficiency for swipe-based sampling systems can provide a better chance of detection when screening for trace explosives or narcotics particles. A technique was developed to improve the particle collection efficiency of commercially-available collection swabs used for field sampling of trace contraband materials. A silicone adhesive was added to Teflon-coated fiberglass swabs to aid in collecting trace levels of contamination from surfaces. Since the swabs are typically used for ion mobility spectrometry (IMS) analysis, it is important for them to produce no chemical background when heated. Results show that the adhesive swabs had a higher particle collection efficiency compared to the untreated swabs by a factor of 12, without negatively interfering with the IMS analysis. It was also found that the adhesive swabs could be reused 10 times without significant reduction in collection efficiency. While it is possible that the adhesive swabs may not be suitable for all surface types due to loss of adhesive material after multiple uses, the benefits of higher particle collection efficiency are extremely promising.

Functionalized, carbon nanotube material for the catalytic degradation of organophosphate nerve agents

AbstractRecent world events have emphasized the need to develop innovative, functional materials that will safely neutralize chemical warfare (CW) agents in situ to protect military personnel and civilians from dermal exposure. Here, we demonstrate the efficacy of a novel, proof-of-concept design for a Cu-containing catalyst, chemically bonded to a single-wall carbon nanotube (SWCNT) structural support, to effectively degrade an organophosphate simulant. SWCNTs have high tensile strength and are flexible and light-weight, which make them a desirable structural component for unique, fabric-like materials. This study aims to develop a self-decontaminating, carbon nanotube-derived material that can ultimately be incorporated into a wearable fabric or protective material to minimize dermal exposure to organophosphate nerve agents and to prevent accidental exposure during decontamination procedures. Carboxylated SWCNTs were functionalized with a polymer, which contained Cu-chelating bipyridine groups, and their catalytic activity against an organophosphate simulant was measured over time. The catalytically active, functionalized nanomaterial was characterized using X-ray fluorescence and Raman spectroscopy. Assuming zeroth-order reaction kinetics, the hydrolysis rate of the organophosphate simulant, as monitored by UV-vis absorption in the presence of the catalytically active nanomaterial, was 63 times faster than the uncatalyzed hydrolysis rate for a sample containing only carboxylated SWCNTs or a control sample containing no added nanotube materials.

Evaluation of a drop-on-demand micro-dispensing system for development of artificial fingerprints

Precision micro-dispensing is an evolving technique that has many applications in the scientific and additive manufacturing communities. Here we describe a method for dispensing viscous materials, including the oily substance found in human fingerprints, known as sebum. In this work, a dispense jet system was used to deposit known amounts of sebum onto surfaces to represent an artificial human fingerprint. Ultraviolet-visible spectrophotometry (UV-Vis) and microgravimetry were used to verify the sebum mass loadings of the samples. The dispense jet was capable of printing a viscous sebum mixture as well as a less viscous solution of sebum dissolved in heptane. This method was shown to be repeatable, and UV-Vis was found to be a simple and useful technique for verifying the mass of sebum deposited. This method could be used to prepare artificial fingerprint samples for a variety of applications including the preparation of test materials for emerging trace detection technologies.

Rapid detection of fentanyl, fentanyl analogues, and opioids for on-site or laboratory based drug seizure screening using thermal desorption DART-MS and ion mobility spectrometry

Fentanyl and fentanyl analogues represent a current and emerging threat in the United States as pure illicit narcotics and in mixtures with heroin. Because of their extreme potency, methods to safely and rapidly detect these compounds are of high interest. This work investigates the use of thermal desorption direct analysis in real time mass spectrometry (TD-DART-MS) and ion mobility spectrometry (IMS) as tools for the rapid and sensitive (nanogram to picograms) detection of fentanyl, 16 fentanyl analogues, and five additional opioids. Competitive ionization studies highlight that detection of these compounds in the presence of heroin is readily achievable, down to 0.1% fentanyl by mass with TD-DART-MS. With IMS, detection of nanogram levels of fentanyl in a binary fentanyl and heroin mixture is possible but can be complicated by decreased resolution in certain commercial instrument models. Modifications to the alarm windows can be used to ensure detection of fentanyl in binary mixtures. Additionally, three complex background matrices (fingerprint residue, dirt, and plasticizers) are shown to have a minimal effect of the detection of these compounds. Wipe sampling of the exterior of bags of questioned powders is shown to be a safe alternative method for field screening and identification, removing the need to handle potentially lethal amounts of material.

Production and characterization of polymer microspheres containing trace explosives using precision particle fabrication technology.

Well characterized test materials are essential for validating the performance of current trace explosive detection systems. These test materials must replicate trace explosive contamination in the form of small particles with characteristic diameters in the micrometer range. In this work, Precision Particle Fabrication was used to fabricate monodisperse polymer microspheres that contain high explosives. Three high explosives were successfully incorporated into the microspheres. Ion mobility spectrometry confirmed that the encapsulation efficiency was typically greater than 50%, with some suspected loss to the aqueous phase during production. This study demonstrates that, with this technique, polymer microspheres containing explosives can be produced with sufficient encapsulation, along with tightly controlled particle size distributions at high production rates. These microspheres have proven to be a valuable test material for trace explosive detectors because of their highly precise size, shape and explosive composition.

Biomimetic Sniffing Improves the Detection Performance of a 3D Printed Nose of a Dog and a Commercial Trace Vapor Detector.

Unlike current chemical trace detection technology, dogs actively sniff to acquire an odor sample. Flow visualization experiments with an anatomically-similar 3D printed dog’s nose revealed the external aerodynamics during canine sniffing, where ventral-laterally expired air jets entrain odorant-laden air toward the nose, thereby extending the “aerodynamic reach” for inspiration of otherwise inaccessible odors. Chemical sampling and detection experiments quantified two modes of operation with the artificial nose-active sniffing and continuous inspiration-and demonstrated an increase in odorant detection by a factor of up to 18 for active sniffing. A 16-fold improvement in detection was demonstrated with a commercially-available explosives detector by applying this bio-inspired design principle and making the device “sniff” like a dog. These lessons learned from the dog may benefit the next-generation of vapor samplers for explosives, narcotics, pathogens, or even cancer, and could inform future bio-inspired designs for optimized sampling of odor plumes.

A chemically relevant artificial fingerprint material for the cross-comparison of mass spectrometry techniques

Abstract The development of a chemically relevant artificial fingerprint material as well as a preliminary method for artificial fingerprint deposition for mass spectrometric analysis and chemical imaging is presented. The material is an emulsified combination of artificial eccrine and sebaceous components designed to mimic the chemical profile of a latent fingerprint. In order to deposit this material in a manner that resembles a latent fingerprint, an artificial fingerprint stamp, created using 3-D printing, was used. Development of this material was spurred by the inability to cross-compare mass spectrometric techniques using real fingerprint deposits because of their inherent heterogeneity. To determine how well this material mimicked the chemical composition of actual fingerprint deposits, ambient ionization mass spectrometry and secondary ion mass spectrometry techniques were used to compare the signatures of the artificial and real fingerprint deposits. Chemical imaging comparisons of the artificial fingerprints across different imaging platforms are also presented as well as a comparison using fingerprint development agents. The use of a material such as this may provide a way to compare the capabilities of different techniques in analyzing a sample as complex as a fingerprint as well as providing a method to create fingerprints with controlled amounts of exogenous material for research and technique validation purposes.

The effect of reusing wipes for particle collection

Sample collection for Ion Mobility Spectrometry (IMS) analysis is typically completed by swiping a collection wipe over a suspect surface to collect trace residues. The work presented here addresses the need for a method to measure the collection efficiency performance of surface wipe materials as a function of the number of times a wipe is used to interrogate a surface. The primary purpose of this study is to investigate the effect of wipe reuse, i.e., the number of times a wipe is swiped across a surface, on the overall particle collection and IMS response. Two types of collection wipes (Teflon coated fiberglass and Nomex) were examined by swiping multiple times, ranging from 0 to 1000, over representative surfaces that are common to security screening environments. Particle collection efficiencies were determined by fluorescence microscopy and particle counting techniques, and were shown to improve dramatically with increased number of swiping cycles. Ion mobility spectrometry was used to evaluate the chemical response of known masses of explosives (deposited after reusing wipes) as a function of the wipe reuse number. Results show that chemical response can be negatively affected, and greatly depends upon the conditions of the surface in which the wipe is interrogating. For most parameters tested, the PCE increased after the wipe was reused several times. Swiping a dusty cardboard surface multiple times also caused an increase in particle collection efficiency but a decrease in IMS response. Scanning electron microscopy images revealed significant surface degradation of the wipes on dusty cardboard at the micrometer spatial scale level for Teflon coated wipes. Additionally, several samples were evaluated by including a seven second thermal desorption cycle at 235°C into each swipe sampling interval in order to represent the IMS heating cycle. Results were similar to studies conducted without this heating cycle, suggesting that the primary mechanism for wipe deterioration is mechanical rather than thermal.

The production of monodisperse explosive particles with piezo-electric inkjet printing technology

We have developed a method to produce discrete microparticles from compounds dissolved in nonpolar or polar solvents using drop-on-demand inkjet printer technology. A piezoelectric inkjet printhead located atop a drying tube produces precise droplets containing defined quantities of analyte. Droplets solidify into microparticles with known composition and size as they traverse down the drying tube. Because this is a drop-on-demand printing process, a known number of droplets are produced providing quantitative particle delivery to a variety of substrates. Particular emphasis is placed on the development and characterization of the drying tube in this work. The drying tube was modeled using computational fluid dynamics and experimentally evaluated using laser-based flow visualization techniques. A notable design feature of the drying tube is the ability to push heated air through the tube rather than the need to pull air from the exit. This provides the ability to place a known number of well-defined particles onto almost any substrate of interest, rather than having to collect particles onto a filter first and then transfer them to another surface. Several types of particles have been produced by this system, examples of which are pure particles of cyclotrimethylenetrinitramine ranging from 10 μm to 30 μm in diameter, and ammonium nitrate particles of 40 μm diameter. The final particle size is directly related to the solute concentration of the printing solution and the size of the initial jetted droplet.