A rapid method for the identification of nitrocellulose in high explosives and smokeless powders using GC–EI–MS

Barbed arrow-like structure membrane with ultra-high rectification coefficient enables ultra-fast, highly-sensitive lateral-flow assay of cTnI

Acute myocardial infarction (AMI) has become a public health disease threatening public life safety due to its high mortality. The lateral-flow assay (LFA) of a typical cardiac biomarker, troponin I (cTnI), is essential for the timely warnings of AMI. However, it is a challenge to achieve an ultra-fast and highly-sensitive assay for cTnI (hs-cTnI) using current LFA, due to the limited performance of chromatographic membranes. Here, we propose a barbed arrow-like structure membrane (BAS Mem), which enables the unidirectional, fast flow and low-residual of liquid. The liquid is rectified through the forces generated by the sidewalls of the barbed arrow-like grooves. The rectification coefficient of liquid flow on BAS Mem is 14.5 (highest to date). Using BAS Mem to replace the conventional chromatographic membrane, we prepare batches of lateral-flow strips and achieve LFA of cTnI within 240 s, with a limit of detection of 1.97 ng mL-1. The lateral-flow strips exhibit a specificity of 100%, a sensitivity of 93.3% in detecting 25 samples of suspected AMI patients. The lateral-flow strips show great performance in providing reliable results for clinical diagnosis, with the potential to provide early warnings for AMI.

A simple voltammetric method to evaluate the firing distance through determination of nitrocellulose

Nitrocellulose (NC) is the main component of propellants for small firearm ammunitions. Even though NC particles are ejected from gun barrels together with bullets and they are often recovered on close-to-muzzle targets, quantitative analysis of nitrocellulose for forensic purposes has been neglected so far. Moreover, although the presence of the nitroester groups makes nitrocellulose electroactive, its electrochemical determination has been poorly considered in literature. In this paper, a quantitative differential pulse voltammetric method for the analysis of nitrocellulose in targets is suggested, with the aim of estimating its concentration decay on targets with increasing the shooting distance. The presented method works in acetonitrile/ethanol/lithium perchlorate, has a LOQ of 4 mg L-1 and linearity up to 2000 mg L-1. Ammunitions loaded with a nitrocellulose/nitroglycerine-based gunpowder were discharged to draw a calibration curve for shooting distance determination in the range from 5 cm to 120 cm. The effect of possible interfering substances (water, nitroglycerine, nitroguanidine, nitrites) was evaluated, and results are compared with literature methods.

Chemical Analysis of Gunpowder and Gunshot Residues

The identification of firearms is of paramount importance for investigating crimes involving firearms, as it establishes the link between a particular firearm and firearm-related elements found at a crime scene, such as projectiles and cartridge cases. This identification relies on the visual comparison of such elements against reference samples from suspect firearms or those existing in databases. Whenever this approach is not possible, the chemical analysis of the gunpowder and gunshot residue can provide additional information that may assist in establishing a link between samples retrieved at a crime scene and those from a suspect or in the identification of the corresponding model and manufacturer of the ammunition used. The most commonly used method for the chemical analysis of gunshot residue is scanning electron microscopy with energy dispersive X-ray, which focuses on the inorganic elements present in ammunition formulation, particularly heavy metals. However, a change in the legal paradigm is pushing changes in these formulations to remove heavy metals due to their potential for environmental contamination and the health hazards they represent. For this reason, the importance of the analysis of organic compounds is leading to the adoption of a different set of analytical methodologies, mostly based on spectroscopy and chromatography. This manuscript reviews the constitution of primer and gunpowder formulations and the analytical methods currently used for detecting, characterising, and identifying their compounds. In addition, this contribution also explores how the information provided by these methodologies can be used in ammunition identification and how it is driving the development of novel applications within forensic ballistics.

Characterization of Electrospinning Prepared Nitrocellulose (NC)-Ammonium Dinitramide (ADN)-Based Composite Fibers

Nanoscale composite energetic materials (CEMs) based on oxidizer and fuel have potential advantages in energy adjustment and regulation through oxygen balance (OB) change. The micro- and nanosized fibers based on nano nitrocellulose (NC)-ammonium dinitramide (ADN) were prepared by the electrospinning technique, and the morphology, thermal stability, combustion behaviors, and mechanical sensitivity of the fibers were characterized by means of scanning electron microscope (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), gas pressure measurement of thermostatic decomposition, laser ignition, and sensitivity tests. The results showed that the prepared fibers with fluffy 3D macrostructure were constructed by the overlap of micro/nanofibers with the energetic particles embedded in the NC matrix. The first exothermic peak temperature (T_p) of the samples containing ADN decreased by 10.1 °C at most compared to that of ADN, and the pressure rise time of all the samples containing ADN moved forward compared to that of the sample containing NC only. Furthermore, ADN can decrease the ignition delay time of NC-based fibers under atmosphere at room temperature from 33 ms to 9 ms and can enhance the burning intensity of NC-based fibers under normal pressure. In addition, compared to the single high explosive CL-20 or RDX, the mechanical sensitivities of the composite materials containing high explosive CL-20 or RDX were much decreased. The positive oxygen balance of ADN and the intensive interactions between ADN and NC can reduce the ignition delay time and promote the burning reaction intensity of NC-based composite fibers, while the mechanical sensitivities of composite fibers could be improved.

A simple organic multi-analyte fluorescent prober: One molecule realizes the detection to DNT, TATP and Sarin substitute gas

The detections of explosives and chemical warfare agents (CWAs) are always important for global security. In this study, a simple donor (D)- acceptor (A) type small organic fluorescent triazole-based molecule (T1) is reported. T1 is composed of a central 4H-1, 2, 4-triazole (TAZ) "core" and three external triphenylamine (TPA) groups. Its spin-coating films can realize the multi-analyte fluorescent prober to detect DNT (2, 4-dinitrotoluene), hydrogen peroxide (H₂O₂, the substitute for triacetone triperoxide (TATP)) and diethylchlorophosphate (DCP, the substitute for Sarin) vapors. Additionally, the combination of the triple sensing mechanism in the different channels affords three distinct sets of output-signal responses, these three hazardous compounds could be identified rapidly with high sensitivity and selectivity: fluorescence turn-off response to DNT, fluorescence turn-on response to H₂O₂ and fluorometric-colorimetric dual-channel response to DCP. T1 fluorescent probe is highly advantageous for concurrently monitoring various hazardous target substances and simultaneously possessing the desirable sensitivity and selectivity, excellent reusability. Hereby, this study provides a prototype method to build novel multifunctional fluorescent probes to explosives and CWAs.

Interpol review of detection and characterization of explosives and explosives residues 2016-2019

This review paper covers the forensic-relevant literature for the analysis and detection of explosives and explosives residues from 2016-2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/Resources/Documents#Publications.

Chemical Classification of Explosives

This work comprehensively reviews some fundamental concepts about explosives and their two commonly used classifications based on either their velocity of detonation or their application. These classifications are highly useful in the military/legal field, but completely useless for the chemical determination of explosives. Because of this reason, a classification of explosives based on their chemical composition is comprehensively revised, discussed and updated. This classification seeks to merge those dispersed chemical classifications of explosives found in literature into a unique general classification, which might be useful for every researcher dealing with the analytical chemical identification of explosives. In the knowledge of the chemical composition of explosives, the most adequate analytical techniques to determine them are finally discussed.

Conjugated Polymer Nanoparticles Based Fluorescent Electronic Nose for the Identification of Volatile Compounds

A fluorescence sensing array (or fluorescent electronic nose) is designed on a disposable paper card using 36 sets of soluble conjugated polymeric nanoparticles (SCPNs) as sensors to easily identify wide ranges of volatile analytes, including explosives and toxic industrial chemicals (amines and pungent acids). A 108-dimensional vector obtained from the fluorescent color change in the sensing array is defined and directly treated as an index in a standard chemical library (30 kinds of volatile analytes and a control group). Hierarchical clustering analysis (HCA) and principal component analysis (PCA) indicated the diversity in electronic structures; saturated vapor pressure and miscibility of analytes are keys in differentiating the analytes, with electron-rich arenes and alkylamines enhancing fluorescence and electron-deficient analytes attenuating fluorescence. A support vector machine (SVM) works well to predict an unknown sample, reaching 99.5% accuracy. The excellent fluorescence stability (no fluorescence quenching after being exposed in air for one month) and high sensitivity (emission color changes within minutes when exposed to analytes) suggest that the fluorescent polymer-based electronic nose will play an important role in field detection and identification of a wide spreading of hazardous substances.

Synthesis of a surface molecular imprinting polymer based on silica and its application in the identification of nitrocellulose

A surface molecular imprinting polymer (MIP) based on silica (SiO₂/MIP) with excellent selective identification properties towards nitrocellulose (NC) was synthesized with methylacrylic acid as a functional monomer and NC as a template molecule, through simple in situ polymerization. The functional groups of SiO₂/MIP were studied through Fourier transform infrared spectroscopy. The morphology, crystalline state and thermostability of SiO₂/MIP were investigated respectively by scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. Binding capacity and selectivity studies of SiO₂/MIP for NC and its analogues were carried out through ultraviolet-visible spectrophotometry. The thermal analysis and study of crystalline states confirmed the successful imprinting of NC in the polymer networks. The optimized conditions were found to be a polymerization temperature of 45 °C and a functional monomer to cross-linking ratio of 1 : 3. The adsorption capacity of SiO₂/MIP was improved considerably compared with that of polymers prepared by traditional imprinting technology, with a maximum adsorption amount of 1.7 mg mg⁻¹ in 2 mg ml⁻¹ NC solution, compared with an adsorption capacity of about 0.5 mg mg⁻¹ for a traditional MIP. According to the selectivity study, more NC was adsorbed by SiO₂/MIP than its analogues; the best adsorption capacity of SiO₂/MIP for NC was approaching 5 times that for carboxymethyl cellulose (CMC). The results show that it would be possible to apply SiO₂/MIP for the detection of NC, to give improved sensitivity in security checking and improved contaminant adsorption.

A novel surface molecular imprinting polymer was prepared which displayed excellent specificity, selectivity and a large adsorption capacity for nitrocellulose.