Opioids are a serious and potentially fatal danger to not only those that abuse the drug, but also to those in law enforcement that depend upon its detection in the field. Certain members of the opioid family are not even intended for human use, but have still found their way into illicit drug sales. First responders require proper training on testing equipment (e.g., ion mobility spectrometry (IMS)) and methods to be employed for safe and rapid detection. IMS instruments are deployed at border patrol points across the U.S. and are capable of nano-gram level detection. Unfortunately, the direct handling of of hazardous and controlled substances during training is still a necessity. Training users with surrogate compounds provides the necessary experience required before encountering any threats posed by opioids, on-site. The reduced ion mobilities of 15 potential surrogate compounds were assessed on a commercially available instrument in order to determine their similarity (i.e. & PLUSMN; 5%) to heroin, fentanyl, and carfentanil. Of those tested, 14 were considered to be useful opioid surrogates. The compounds that exhibited similar reduced ion mobilities to heroin, fentanyl and carfentanil were cut with lactose and acetaminophen to assess matrix effects. Compounds exhibiting similar reduced ion mobilities to the target opioids under all conditions can be considered for application in IMS training for hazardous opioids.

Opioid exposure is an important hazard that law enforcement officers, first responders, and forensic technicians face during training and in the line of duty. Development of opioid sensing capabilities and training personnel in their use is therefore imperative. However, because of their toxicity and controlled status, many opioids are difficult and dangerous to work with directly for the development and testing of sensors. Here, we analyze a number of non-toxic and less-toxic surrogates of three prevalent opioids (heroin, fentanyl, and carfentanil) for their ability to closely mimic infrared, Raman, and surface-enhanced Raman spectroscopic properties of the parent compounds. We examine the spectroscopic behavior of each of the compounds in pure form as well as diluted with lactose and acetaminophen, two common cutting agents encountered in the field. We find a number of compounds which can be used as surrogates for opioids in spectroscopic sensor development and training. The use of these surrogates will mitigate the risk undertaken during sensor development and training of law enforcement and first responders.

Opioids pose a serious risk to the medical health of abusers, as well as law enforcement officials that come into contact with suspicious materials that may require presumptive testing or handling. Because milligram or less quantities of certain opioids are considered lethal, first responders must be properly trained on the procedures and safe application of presumptive testing kits (e.g. colorimetric). These kits are generally portable, provide rapid results and rely on the chemical substructures of the target compounds. Clearly, incorporating the direct handling of opioids into training on these testing kits would be considered undesirable. Training users with surrogate compounds minimizes this hazard before on-scene deployment. A total of 17 surrogate compounds for heroin, fentanyl and carfentanil were identified, with each of these compounds bearing many of the same functional groups, structural features and approximate or exact molecular weights possessed by the parent opioid. Commercially available colorimetric testing kits were employed to examine the capability of these compounds to effectively serve as surrogates. Of those tested, 13 were considered to be highly effective surrogates for these kits. The most promising surrogates were cut with lactose and acetaminophen in order to assess matrix effects.

The transport efficiency of 2,4-dinitrotoluene (2,4-DNT), 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-triazinane (RDX) trace vapors through tubing materials that commonly constitute vapor handling infrastructures have been determined for a variety of tubing dimensions and sampling conditions. Using a programmable temperature vaporization inlet coupled with a gas chromatography mass spectrometer (PTV-GC-MS), the explosive vapors were quantified both with and without a length of tubing of a specific material in the sampling flow path. At vapor temperatures of 30 °C and 66 °C, minimal attenuations were observed for 2,4-DNT and TNT vapor concentrations when the tubing material was in-line with the sampling flow path, indicating that the transport is largely unaffected by interactions with the surface of the tubing materials. In contrast, RDX vapors showed large attenuations as a function of both sampling conditions and tubing materials/dimensions. For those experiments where attenuated RDX vapor transport was observed, the mass sequestered by interactions between the flowing vapor and the internal tubing surface was determined to be in the range of tens to hundreds of picograms. Of all the materials examined for RDX transport, fluorinated ethylene propylene (FEP) tubing resulted in the least amount of mass loss to surface interactions, with vapor transport efficiencies (VTEs) between 95-100%. However, for some materials, the combination of tubing dimensions and sampling conditions resulted in no RDX transport, even after sampling more than 250.0 L of vapor through the tubing.

The continual or on-demand delivery of aerosol is important for sensor validation and the development of trace particle detection methodologies. The system presented here operates by introducing aerosolized analytical standard solutions in a heated air flow, generating vapor phase analytes that are subsequently transported and cooled to provide aerosolized particles. The notable design feature was a small concentric air flow device that blends chilled dry air with vapor phase analyte to induce a phase transition without the need for volatile organic solvents. While organic solvents accelerate solvent evaporation, they present potential interferences for downstream sensors. Cyclotrimethylenetrinitramine (RDX) particles were generated and optically counted from the exhaust plume aerosol. The solid RDX material was binned into 1-2.5, 2.5-5, 5-10, and 10+ mu m diameter sizes and when the system was actively cooled, the generation of particles exhibited a relative increase of 4.9%, 27.6%, 95.6%, and 78.0% in production, respectively. When observed under a microscope, collected RDX particles ranged from about 1 to 7 mu m in diameter. It was determined that the production of solid material was proportional to the temperature and mass loading of the vapor, as dictated by the feed solution concentration; cooler temperatures and higher concentrations led to the increased production of particles ranging from 1 to 10 mu m in diameter for the low-vapor pressure analytes studied: RDX (cyclotrimethylenetrinitramine), PETN (pentaerythritol tetranitrate), TNT (2-methyl-1,3,5-trinitrobenzene), and 2,6-DNT (2,6-dinitrotoluene).

The Trace Vapor Generator for Explosives and Narcotics (TV-Gen) is a portable and compact instrument designed to deliver a continuous source of trace-level vapors and vapor mixtures. It provides a tool to assist in the independent validation and verification of new materials and sensors under development for the vapor detection of explosives and narcotics. The design was conceived for use with a broad range of analytes, detection systems, materials, and sensors and to switch easily between the clean and analyte vapor streams. The TV-Gen system utilizes nebulization of aqueous analyte solutions, an oven to promote efficient transport, and a control box that provides dedicated computer control with logging capabilities. Resultant vapor streams are stable over several hours, with the vapor concentration controlled by a combination of aqueous analyte solution concentration, liquid flow rate through the nebulizer, and volume flow rate of air through the TV-Gen manifold.

Flow-through optical chromatography (FT-OC), an advanced mode of optical chromatography, achieved baseline separation of a mixture of silica microparticles (SiO2, 1.00 and 2.50 μm) and a mixture of polystyrene microparticles (PS, 1.00, 2.00, and 3.00 μm) based on particle size. Comparisons made between experimentally determined velocities for the microparticles and theoretically derived velocities from Mie theory and Stokes' law validated the data collection setup and the data analysis for FT-OC. A population shift in live macrophages (cell line IC-21, ATCC TIB-186) responding to environmental stimuli was sensitively detected by FT-OC. The average velocity of macrophages stressed by nutritional deprivation was decreased considerably together with a small but statistically significant increase in cell size. Mie scattering calculations demonstrated that the small increase in cell size of macrophages stressed by nutritional deprivation was not entirely responsible for this decrease. Confocal fluorescence microscopy and atomic force microscopy (AFM) studies revealed morphological changes of macrophages induced by nutritional deprivation, and these changes were more likely responsible for the decrease in average velocity detected by FT-OC. Confocal Raman microspectroscopy was used to shed light upon biochemical transformations of macrophages suffering from nutritional deprivation.

Phosphatase-encapsulated nanotubes have potential in environmental remediation of organophosphate contaminants (e.g., pesticides, nerve agents). We investigated alkaline phosphatase (AP) activity when encapsulated in self-assembled lithocholic acid nanotubes (LCA-AP) in water samples along a transect from Cypress bog headwaters through estuarine waters and to Atlantic Ocean seawater. Apparent Vmax (appVmax) for both LCA-AP and unencapsulated AP (Free-AP) was most rapid at mid-estuary and most inhibited at the humic-rich bog. LCA-AP retained a higher-activity percentage, suggesting that encapsulation may afford some protection from denaturing effects of humics. Apparent Km (appKm) of Free-AP (1–2.3 μM) was largely unaffected by preincubation with transect water, whereas appKm of LCA-AP was higher with bog water (5.3 μM) relative to other stations. When comparing Free-AP and LCA-AP, increasing salinity generally decreased the catalytic efficiency of the LCA-AP, but had little effect on that of the Free-AP. ...

Micellar electrokinetic chromatography (MEKC) is a mode of capillary electrophoresis that allows for the separation of neutral molecules in an electric field. Typically, neutral molecules move with electroosmotic flow (EOF) or bulk flow during electrophoretic separations resulting in no temporal resolution between mixtures of neutral analytes. Inclusion of surfactant micelles in the separation buffer allows for the separation of neutral analytes from one another through association with the micelle. Here we outline the implementation of MEKC for the separation of neutral molecules using a mixture of nitroaromatic explosives and their degradation products serving as a test analyte mixture.

A novel vapor delivery testbed, referred to as the Trace Explosives Sensor Testbed, or TESTbed, is demonstrated that is amenable to both high- and low-volatility explosives vapors including nitromethane, nitroglycerine, ethylene glycol dinitrate, triacetone triperoxide, 2,4,6-trinitrotoluene, pentaerythritol tetranitrate, and hexahydro-1,3,5-trinitro-1,3,5-triazine. The TESTbed incorporates a six-port dual-line manifold system allowing for rapid actuation between a dedicated clean air source and a trace explosives vapor source. Explosives and explosives-related vapors can be sourced through a number of means including gas cylinders, permeation tube ovens, dynamic headspace chambers, and a Pneumatically Modulated Liquid Delivery System coupled to a perfluoroalkoxy total-consumption microflow nebulizer. Key features of the TESTbed include continuous and pulseless control of trace vapor concentrations with wide dynamic range of concentration generation, six sampling ports with reproducible vapor profile outputs, limited low-volatility explosives adsorption to the manifold surface, temperature and humidity control of the vapor stream, and a graphical user interface for system operation and testing protocol implementation.

The generation of trace 2,4,6-trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), and pentaerythritol tetranitrate (PETN) vapors using a pneumatically modulated liquid delivery system (PMLDS) coupled to a polytetrafluoroethylene (PTFE) total-consumption micronebulizer is presented. The vapor generator operates in a continuous manner with final vapor concentrations proportional to the explosive concentration in aqueous solution delivered through the nebulizer and the diluent air flow rate. For quantitation of concentrations in the parts per billionvolume (ppbv) to parts per trillionvolume (pptrv) range, Tenax-TA thermal desorption tubes were used for vapor collection with subsequent analysis on a thermal-desorption system programmable-temperature vaporization gas chromatograph (TDS-PTV-GC) with a μ-ECD detector. With 30 min sample times and an average sampling rate of 100 mL min(-1), vapor concentrations of 38 pptrv for TNT, 25 pptrv for RDX, and 26 pptrv for PETN were determined. For parts per quadrillionvolume (ppqv) vapor quantitation of TNT and RDX, an online PTV-GC system with a negative-ion chemical ionization mass spectrometer (methane reagent gas) was used for direct sampling and capture of the vapor on the PTV inlet. Vapor concentrations as low as 160 ppqv and 710 ppqv for TNT and RDX were quantified, respectively, with an instrument duty cycle as low as 4 min.

Hexamethylene triperoxide diamine (HMTD) is an easily synthesized and highly sensitive organic peroxide frequently used as a primary explosive. The vapor pressure of HMTD is very low, impeding vapor detection, especially when compared to other peroxide explosives, such as triacetone triperoxide (TATP) or diacetone diperoxide (DADP). Despite this fact, HMTD has a perceptible odor that could be utilized in the indirect detection of HMTD vapor. Headspace measurements above solid HMTD samples confirm that HMTD readily decomposes under ambient conditions to form highly volatile products that include formic acid, ammonia, trimethylamine and formamides. The presence and quantity of these compounds are affected by storage condition, time, and synthetic method, with synthetic method having the most significant effect on the content of the headspace. A kinetic study of HMTD decomposition in solution indicated a correlation between degradation rate and the presence of decomposition species identified in the headspace, and provided further insight into the mechanism of decomposition. The study provided evidence for a proton assisted decomposition reaction with water, as well as an intramolecular decomposition process facilitated by the presence of water.

Horseradish peroxidase (HRP) was encapsulated in self-assembled lithocholic acid (LCA) based organic nanotubes and its catalytic activity before and after thermal treatment was measured for comparison with free HRP. The apparent kcat (kcat/Km) for nanotube encapsulated HRP remained almost the same before and after thermal treatment, reporting an average value of 3.7 ± 0.4 μM(-1) s(-1). The apparent kcat value for free HRP decreased from 14.8 ± 1.3 μM(-1) s(-1) for samples stored at 4 °C to 2.4 ± 0.1 μM(-1) s(-1) after thermal treatment for 8 h at 55 °C. The Michaelis-Menten constants, Km, determined for encapsulated HRP and free HRP were relatively unperturbed by storage conditions at 4 °C or thermally treated at 55 °C for varying time periods from 2-8 h, with encapsulated HRP having a slightly higher Km than free HRP (13.4 ± 0.9 μM versus 11.7 ± 0.4 μM). The amount of HRP encapsulated in LCA nanotubes increased dramatically when the mixture of HRP and LCA nanotubes was brought to an elevated temperature. Within 4 h of thermal treatment at 55 °C, the amount of HRP encapsulated by the LCA nanotubes was more than 4 times the amount of HRP encapsulated when equilibrated at 4 °C for 7 days. Molecular dynamics (MD) simulations show that the higher degree of exposure of hydrophobic residues in HRP at elevated temperatures enhances the hydrophobic interaction between HRP and the nanotube wall, resulting in the increased amount of HRP surface adsorption and, hence, the overall amount of encapsulation inside the nanotubes.

Organic nanotubes form in aqueous solution near physiological pH by self-assembly of lithocholic acid (LCA) with inner diameters of 20–40nm. The encapsulation of enhanced green fluorescent protein (eGFP) and resultant confinement effect for eGFP within these nanotubes is studied via confocal microscopy. Timed release rate studies of eGFP encapsulated in LCA nanotubes and fluorescence recovery after photobleaching (FRAP) indicate that the diffusive transport of eGFP out of and/or within the nanotubes is very slow, in contrast to the rapid introduction of eGFP into the nanotubes. By encapsulating two fluorescent proteins in LCA nanotubes, eGFP and mCherry, as a fluorescence resonance energy transfer (FRET) pair, the FRET efficiencies are determined using FRET imaging microscopy at three different protein concentrations with a fixed donor-to-acceptor ratio of 1:1. Förster theory reveals that the proteins are spatially separated by 4.8–7.2nm in distance inside these nanotubes. The biomimetic nanochannels of LCA nanotubes not only afford a confining effect on eGFP that results in enhanced chemical and thermal stability under conditions of high denaturant concentration and temperature, but also function as protein concentrators for enriching protein in the nanochannels from a diluted protein solution by up to two orders of magnitude.

Ammonium nitrate (AN) is an ionic solid commonly used as a fertilizer and in commercial blasting applications. Frequently, AN is mixed with a fuel and used in improvised explosives devices (IEDs). To characterize the low-volatility components emanating from AN, a sample of AN was sealed inside a stainless steel chamber while a laminar flow of air swept the headspace vapor components into a water impinger or cold-trap for pre-concentration and subsequent analysis by ion chromatography (IC). Both collection methods were found to be 100% efficient for collecting nitric acid vapor, whereas the collection efficiency for ammonia was dependent upon the collection method and, for the water impinging method, additionally upon the vapor concentration, humidity and flow rate. Cold-trapping efficiency for ammonia was 4% +/- 2% across all parameters studied. Water impinging was more efficient (20-70%), but the efficiency varied according to each of the aforementioned variables. The characteristics of an AN vapor generated from a solid sample were found to vary as the sample approached equilibrium inside the chamber. Initially, large quantities of ammonia were observed, but as a steady state was achieved within the laminar flow and a dynamic equilibrium established, the ratio of ammonia to nitric acid in the effluent vapor dropped, although never becoming equimolar. The ratio was strongly dependent upon humidity.

A novel analytical method has been developed for the quantitation of trace levels of ammonia in the headspace of ammonium nitrate (AN) using derivatized solid phase microextraction (SPME) fibers with gas chromatography mass spectrometry (GC-MS). Ammonia is difficult to detect via direct injection into a GC-MS because of its low molecular weight and extreme polarity. To circumvent this issue, ammonia was derivatized directly onto a SPME fiber by the reaction of butyl chloroformate coated fibers with the ammonia to form butyl carbamate. A derivatized externally sampled internal standard (dESIS) method based upon the reactivity of diethylamine with unreacted butyl chloroformate on the SPME fiber to form butyl diethylcarbamate was established for the reproducible quantification of ammonia concentration. Both of these compounds are easily detectable and separable via GC-MS. The optimized method was then used to quantitate the vapor concentration of ammonia in the headspace of two commonly used improvised explosive device (IED) materials, ammonium nitrate fuel oil (ANFO) and ammonium nitrate aluminum powder (Ammonal), as well as identify the presence of additional fuel components within the headspace.

A novel liquid injection vapor generator (LIVG) is demonstrated that is amenable to low vapor pressure explosives, 2,4,6-trinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine. The LIVG operates in a continuous manner, providing a constant and stable vapor output over a period of days and whose concentration can be extended over as much as three orders of magnitude. In addition, a large test atmosphere chamber attached to the LIVG is described, which enables the generation of a stable test atmosphere with controllable humidity and temperature. The size of the chamber allows for the complete insertion of testing instruments or arrays of materials into a uniform test atmosphere, and various electrical feedthroughs, insertion ports, and sealed doors permit simple and effective access to the sample chamber and its vapor.