Synthesis and Degradation of Hexamethylene Triperoxide Diamine (HMTD)

Selectivity of Explosives Analysis with Ambient Ionization Single Quadrupole Mass Spectrometry: Implications for Trace Detection

Ambient ionization (AI) is a rapidly growing field in mass spectrometry (MS). It allows for the direct analysis of samples without any sample preparation, making it a promising technique for the detection of explosives. Previous studies have shown that AI can be used to detect a variety of explosives, but the exact gas-phase reactions that occur during ionization are not fully understood. This is further complicated by differences in mass spectrometers and individual experimental set ups between researchers. This study investigated the gas-phase ion reactions of five different explosives using a variety of AI techniques coupled to a Waters QDa mass spectrometer to identify selective ions for explosive detection and identification based on the applied ambient ionization technique. The results showed that the choice of the ion source can have a significant impact on the number of ions observed. This can affect the sensitivity and selectivity of the data produced. The findings of this study provide new insights into the gas-phase ion reactions of explosives and could lead to the development of more sensitive and selective AI-based methods for their detection.

Rapid and selective screening of organic peroxide explosives using acid-hydrolysis induced chemiluminescence

Organic peroxide explosives (OPEs) are unstable, non-military, contemporary security threats often found in improvised explosive devices. Chemiluminescence (CL) can be used to detect OPEs, via radical formation consisting of peroxide moieties (-O-O-) under acidic conditions. However, selectivity for specific OPEs is hampered by the ubiquitous background of H₂O₂. Herein, we report the differentiation of hexamethylene triperoxide diamine (HMTD), triacetone triperoxide (TATP), and methyl ethyl ketone peroxide (MEKP) by specific flow injection analysis-CL (FIA-CL) signal profiles, after H₂SO₄ treatment. The radical degradation pathway of each structure, and its corresponding FIA-CL profile, was explored using mass spectrometry to reveal the rapid loss of -O-O- from TATP and HMTD structures, while MEKP formed CL signal-sustaining oligomers, as opposed to the immediate attenuation of H₂O₂. The CL response for OPEs in an aqueous media, measured via the described FIA-CL method, enabled ultra-trace limits of detection down to 0.40 μM for MEKP, 0.43 μM for HMTD, and 0.40 μM for TATP (combined linear range 1-83 μM with 95% confidence limit, n = 12). Expanded uncertainties of measurement (UM) of MEKP = ±0.98, HMTD = ±1.03, and TATP = ±1.1 (UM included probabilities of false positive and false negative as well as standard deviations of % recoveries and limit of detections of OPEs). Direct aqueous sample introduction via FIA-CL thus offers the prospect of rapid and selective screening of OPEs in security-heightened settings (e.g., airports), averting false positives from more ubiquitous H₂O₂.

Paper spray ionization-high-resolution mass spectrometry (PSI-HRMS) of peroxide explosives in biological matrices

Mitigation of the peroxide explosive threat, specifically triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD), is a priority among the law enforcement community, as scientists and canine (K9) units are constantly working to improve detection. We propose the use of paper spray ionization-high-resolution mass spectrometry (PSI-HRMS) for detection of peroxide explosives in biological matrices. Occurrence of peroxide explosives and/or their metabolites in biological samples, obtained from urine or blood tests, give scientific evidence of peroxide explosives exposure. PSI-HRMS promote analysis of samples in situ by eliminating laborious sample preparation steps. However, it increases matrix background issues, which were overcome by the formation of multiple alkali metal adducts with the peroxide explosives. Multiple ion formation increases confidence when identifying these peroxide explosives in direct sample analysis. Our previous work examined aspects of TATP metabolism. Herein, we investigate the excretion of a TATP glucuronide conjugate in the urine of bomb-sniffing dogs and demonstrate its detection using PSI from the in vivo sample.

In vitro metabolism of HMTD and blood stability and toxicity of peroxide explosives (TATP and HMTD) in canines and humans

Triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) are prominent explosive threats. Mitigation of peroxide explosives is a priority among the law enforcement community, with canine (K9) units being trained to recognise the scent of peroxide explosives. Herein, the metabolism, blood distribution, and toxicity of peroxide explosives are investigated.HMTD metabolism studies in liver microsomes identified two potential metabolites, tetramethylene diperoxide diamine alcohol aldehyde (TMDDAA) and tetramethylene peroxide diamine dialcohol dialdehyde (TMPDDD).Blood stability studies in dogs and humans showed that HMTD was rapidly degraded, whereas TATP remained for at least one week.Toxicity studies in dog and human hepatocytes indicated minimum cell death for both TATP and HMTD.

A Review of the Types of Training Aids Used for Canine Detection Training

The canine detection community is a diverse one, ranging from scientific fields such as behavior, genetics, veterinary medicine, chemistry, and biology to applications in law enforcement, military, medicine, and agricultural/environmental detection. This diversity has allowed for a flourishing and innovative community, yet it has also led to little acceptance and agreement on terminology. This is especially true when discussing the variety of training aids used in olfactory-based exercises. In general, authentic materials and pseudo-scents are the most commonly discussed, with the former accepted widely for training and certification, and the latter more often disregarded. However, as advances are made in the creation of training materials, alternative training aids are being introduced that do not fit into either of these categories. The misconceptions surrounding how these alternative training aids are manufactured has led to confusion on their classification, and therefore their reliance as an effective tool. This manuscript will review the existing language surrounding canine training aids, address relevant research revealing effectiveness, and clarify the different types based on their manufacture, chemical nature, and fundamental function.