Two-temperature preparation method for PDMS-based canine training aids for explosives.

Canine training aids based on vapor capture-and-release into a flexible polymer, polydimethylsiloxane (PDMS), have been used for in canine detection of explosives that have volatile or semi-volatile odorants. To enhance the rate of odor capture for less volatile targets, two temperatures are used for aid preparation. By using an elevated temperature for the target explosive, the amount of vapor is enhanced, increasing the production of the characteristic odor profile.

High separation efficiency of gold nanomaterials of different aspect ratio and size using capillary transient isotachophoresis.

Two modes of capillary electrophoresis (CE), capillary zone electrophoresis (CZE) and capillary transient isotachophoresis (ctITP), were compared for the detection and separation of spherical gold nanoparticles (AuNPs) and gold nanorods (AuNRs). The development of ctITP using two different leading ions is described. Overall, when compared to traditional capillary zone electrophoresis (CZE), ctITP resulted in improved peak shape and peak efficiency.

PEGylation of zinc nanoparticles amplifies their ability to enhance olfactory responses to odorant.

Olfactory responses are intensely enhanced with the addition of endogenous and engineered primarily-elemental small zinc nanoparticles (NPs). With aging, oxidation of these Zn nanoparticles eliminated the observed enhancement. The design of a polyethylene glycol coating to meet storage requirements of engineered zinc nanoparticles is evaluated to achieve maximal olfactory benefit.

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.

After oxidation, zinc nanoparticles lose their ability to enhance responses to odorants.

Electrical responses of olfactory sensory neurons to odorants were examined in the presence of zinc nanoparticles of various sizes and degrees of oxidation. The zinc nanoparticles were prepared by the underwater electrical discharge method and analyzed by atomic force microscopy and X-ray photoelectron spectroscopy. Small (1.

Improvements in the vapor-time profile analysis of explosive odorants using solid-phase microextraction.

A modified approach for characterization of the vapor-time profile of the headspace odors of explosives was developed using solid-phase microextraction (SPME) incorporating introduction of an externally-sampled internal standard (ESIS) followed by gas chromatography/mass spectrometry (GC/MS) analysis. With this new method, reproducibility of the measurements of 2-ethyl-1-hexanol and cyclohexanone were improved compared to previous work (Hoffman et al., 2009; Arthur and Pawliszyn, 1990) through the use of stable-isotope-labeled internal standards.

Engineered metal nanoparticles in the sub-nanomolar levels kill cancer cells.

Background: Small metal nanoparticles obtained from animal blood were observed to be toxic to cultured cancer cells, whereas noncancerous cells were much less affected. In this work, engineered zinc and copper metal nanoparticles were produced from bulk metal rods by an underwater high-voltage discharge method. The metal nanoparticles were characterized by atomic force microscopy and X-ray photoelectron spectroscopy.

Simplified ultrasonically- and microwave-assisted solvent extractions for the determination of ginsenosides in powdered Panax ginseng rhizomes using liquid chromatography with UV absorbance or electrospray mass spectrometric detection.

New approaches for the recovery of ginsenosides are presented that greatly simplify the liquid chromatographic (LC) determination of the total content of eight ginsenosides (Rb1, Rb2, Rc, Rd, Re, Rf, Rg1 and Rg2) in powdered Panax ginseng rhizomes. The extraction protocols not only recover the neutral ginsenosides, but also simultaneously incorporate base-catalyzed hydrolysis of the malonyl-ginsenosides using dilute potassium hydroxide added to the methanol-water extractant. This eliminates the need for an independent extraction step followed by acid- or base-catalyzed hydrolysis.

Reproducible vapor-time profiles using solid-phase microextraction with an externally sampled internal standard.

Determination of the dynamic nature of vapor/odor release has application in a wide variety of systems. This study applies automated solid-phase microextraction (SPME) utilizing an externally sampled internal standard (ESIS) to determine the vapor-time profile of odor delivery devices for three classes of explosive compounds. The profiles of delivery systems for target odorants 2,4-dinitrotoluene (2,4-DNT), 2-ethyl-1-hexanol (2-EH), and triacetone triperoxide (TATP) as canine training aids were compared over a period of 70 h.

Development of SRM 2907 trace terrorist explosives simulants for the detection of Semtex and triacetone triperoxide.

Effective and accurate detection of trace explosives is crucial in the effort to thwart terrorist explosives attacks. A National Institute of Standards and Technology (NIST) standard reference material (SRM) has been developed for the evaluation of trace explosives detectors that sample by collection of residue particles using swiping or air filtration. SRM 2907 Trace Terrorist Explosives Simulants consists of two materials individually simulating the residues of the plastic explosive Semtex [for pentaerytritol tetranitrate (PETN)] and the improvised explosive triacetone triperoxide (TATP).

Evaluating headspace component vapor-time profiles by solid-phase microextraction with external sampling of an internal standard.

The vapor-time profiles of explosive materials are of valuable interest to Homeland Security, providing critical information that can aid in the detection of explosive-containing devices. An approach is described that achieves reproducible characterization of volatile components as a function of time based on comparison of the sample response to an externally sampled internal standard (ESIS). Utilizing nonequilibrium solid-phase microextraction (SPME) measurements, this SPME-ESIS technique improves reproducibility (reported as percent relative standard deviation) of vapor-time profiles by approximately an order of magnitude and allows for an equitable comparison of the target compound between diverse materials.

Evaluation of vapor profiles of explosives over time using ATASS (Automated Training Aid Simulation using SPME).

Despite numerous instrumental achievements, canines are still considered the most effective field method for explosive detection. However, due to strict explosive regulations and safety requirements, it can be a challenge for agencies with "bomb dogs" to train using neat explosive materials. This establishes a need for non-explosive canine training aids with the same volatile component profiles as the explosives that they represent.

A NIST standard reference material (SRM) to support the detection of trace explosives.

SRM 2905 Trace Particulate Explosives was developed to simulate the residues produced by handling plastic and military explosives. A series of nine candidate materials were prepared by coating chromatographic supports with either Composition C-4 (containing RDX (hexahydro-1,3,5-trinitro-1,3,5-Triazine) and HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-Tetrazocine)) or TNT (2,4,6-trinitrotoluene). Criteria for selection of the best material for the SRM included: coating efficiency, extractability with organic solvents, thermal storage stability, consistency of the particle size with fingerprint residues, and suitability for calibration of trace explosives detectors.

The effect of aniline concentration in the ligand exchange reaction with citrate-stabilized gold nanoparticles.

Sodium citrate reduction of hydrogen tetrachloroaurate is one of the most efficient routes in the synthesis of gold nanoparticles (AuNPs). However, a major limitation of this method is that it results only in citrate-stabilized AuNPs, and exchange reactions of the citrate for another stabilizer must be undertaken in cases where other surface functionalities are desired. These exchange reactions can be studied using a variety of techniques.

Reactions of the amine-containing drugs fluoxetine and metoprolol during chlorination and dechlorination processes used in wastewater treatment.

The reactivities of the amine-containing pharmaceuticals fluoxetine and metoprolol with hypochlorite were studied using conditions that simulate wastewater disinfection including neutral pH (7.0), a range of reaction times (2-60 min), and a molar excess of hypochlorite relative to the pharmaceutical concentration (5.7 times).

Transformation of acetaminophen by chlorination produces the toxicants 1,4-benzoquinone and N-acetyl-p-benzoquinone imine.

The reaction of the common pain reliever acetaminophen (paracetamol, 4-acetamidophenol) with hypochlorite was investigated over time under conditions that simulate wastewater disinfection. Initially, the reaction was studied in pure water at neutral pH (7.0), a range of reaction times (2-90 min), and a molar excess of hypochlorite (2-57 times) relative to the acetaminophen concentration.

Making chlorine greener: performance of alternative dechlorination agents in wastewater.

The residual chlorine in chlorine-disinfected and dechlorinated wastewater was characterized using a liquid chromatograph that was switched between reversed-phase separation and flow injection analysis modes, permitting measurement of fractionated and total residual chlorine, respectively. Residuals were detected in the effluent of an operating wastewater treatment plant employing chlorine disinfection and sulfite dechlorination. Despite dechlorination, an estimated total residual chlorine of 3 microM (0.

Making chlorine greener: investigation of alternatives to sulfite for dechlorination.

Inorganic and organic chloramines pose a threat to aquatic ecosystems that are exposed to discharges of treated and disinfected wastewater. Conventionally practiced dechlorination with sulfite reduces the most refractory organic chloramines too slowly to produce wastewater effluents that meet current ecosystem protection criteria in the United States (i.e.

Production of macromolecular chloramines by chlorine-transfer reactions.

Chlorination of treated wastewaters is undertaken to prevent dispersal of human pathogens into the environment. Except in well-nitrified effluents, the primary agents in chlorination, Cl2(g) or NaOCl(aq), are short-lived and quickly transfer oxidative chlorine to secondary agents (N-chloramines), which then participate in the disinfection process. Maturation of residual chlorine resulting from chlorine-transfer reactions is still poorly characterized.

Hair combing to collect organic gunshot residues (OGSR).

A protocol is presented for the collection and analysis of gunshot residues (GSR) from hair. A fine-toothed comb is used for collection of the residues. A small zip-closure bag serves as a container for both sample storage and extraction of the characteristic organic powder additives.

A quantitative comparison of smokeless measurements.

Measurements of the type and concentration of propellant and stabilizer additives in smokeless gunpowder are used by forensic scientists investigating the source of explosives and by military laboratories assuring the safety and efficacy of munitions. The National Institute of Standards and Technology recently assessed the state-of-the-practice of smokeless powder measurements through an international measurement comparison exercise. We here present results provided by the five participants (of 20 total) reporting quantitative as well as qualitative values for two handgun reloading powders.

Improving the recoveries of unstable N-chloramines determined by liquid chromatography-postcolumn electrochemical detection.

Liquid chromatographic (LC) measurement of individual N-chloramines, which are key byproducts of wastewater and drinking water chlorination, could lead to more effective control of water disinfection. Such measurements are challenging because of analyte instability. A detector selective for N-chloramines is constructed based on postcolumn derivatization with iodide followed by reductive detection of the iodine product at a glassy carbon electrode.

A qualitative comparison of smokeless powder measurements.

In the spring of 2000, the National Institute of Standards and Technology and nineteen participants conducted a comparison of smokeless powder additive compositional measurements. The purpose of this exercise was to determine the state-of-the-practice for forensic smokeless powder determinations. For the comparison, two handgun reloading powder samples were mixed and were compositionally evaluated for homogeneity by NIST.

Associating gunpowder and residues from commercial ammunition using compositional analysis.

Qualitatively identifying and quantitatively determining the additives in smokeless gunpowder to calculate a numerical propellant to stabilizer (P/S) ratio is a new approach to associate handgun-fired organic gunshot residues (OGSR) with unfired powder. In past work, the P/S values of handgun OGSR and cartridges loaded with known gunpowders were evaluated. In this study, gunpowder and residue samples were obtained from seven boxes of commercial 38 caliber ammunition with the goals of associating cartridges within a box and matching residues to unfired powders, based on the P/S value and the qualitative identity of the additives.