Selective detection of trace nitroaromatic, nitramine, and nitrate ester explosive residues using a three-step fluorimetric sensing process: a tandem turn-off, turn-on sensor

Detection of trace quantities of explosive residues plays a key role in military, civilian, and counter-terrorism applications. To advance explosives sensor technology, current methods will need to become cheaper and portable while maintaining sensitivity and selectivity. The detection of common explosives including trinitrotoluene (TNT), cyclotrimethylenetrinitramine, cyclotetramethylene-tetranitramine, pentaerythritol tetranitrate, 2,4,6-trinitrophenyl-N-methylnitramine, and trinitroglycerin may be carried out using a three-step process combining "turn-off" and "turn-on" fluorimetric sensing. This process first detects nitroaromatic explosives by their quenching of green luminescence of polymetalloles (lambda em approximately 400-510 nm). The second step places down a thin film of 2,3-diaminonaphthalene (DAN) while "erasing" the polymetallole luminescence. The final step completes the reaction of the nitramines and/or nitrate esters with DAN resulting in the formation of a blue luminescent traizole complex (lambda(em) = 450 nm) providing a "turn-on" response for nitramine and nitrate ester-based explosives. Detection limits as low as 2 ng are observed. Solid-state detection of production line explosives demonstrates the applicability of this method to real world situations. This method offers a sensitive and selective detection process for a diverse group of the most common high explosives used in military and terrorist applications today.     

Particle characteristics of trace high explosives: RDX and PETN

The sizes of explosives particles in fingerprint residues produced from C-4 and Semtex-1A were investigated with respect to a fragmentation model. Particles produced by crushing crystals of RDX and PETN were sized by using scanning electron microscopy, combined with image analysis, and polarized light microscopy was used for imaging and identifying explosive particles in fingerprint residues. Crystals of RDX and PETN fragment in a manner that concentrates mass in the largest particles of the population, which is common for a fragmentation process. Based on the fingerprints studied, the particle size to target for improving mass detection in fingerprint residues by ion mobility spectrometry (IMS) is > or = 10 microm in diameter. Although particles smaller than 10 microm in diameter have a higher frequency, they constitute < 20% of the total mass. Efforts to improve collection efficiency of explosives particles for detection by IMS, or other techniques, must take into consideration that the mass may be concentrated in a relatively few particles that may not be homogeneously distributed over the fingerprint area. These results are based on plastic-bonded explosives such as C-4 that contain relatively large crystals of explosive, where fragmentation is the main process leading to the presence of particles in the fingerprint residues.     

Visual detection of trace nitroaromatic explosive residue using photoluminescent metallole-containing polymers

The detection of trace explosives is important for forensic, military, and homeland security applications. Detection of widely used nitroaromatic explosives (trinitrotoluene [TNT], 2,4-dinitrotoluene [DNT], picric acid [PA]) was carried out using photoluminescent metallole-containing polymers. The method of detection is through the quenching of fluorescence of thin films of the polymer, prepared by spray coating organic solutions of the polymer, by the explosive analyte. Visual quenching of luminescence (lambda(em) approximately 400-510 nm) in the presence of the explosive is seen immediately upon illumination with near-UV light (lambda(ex)=360 nm). Detection limits were observed to be as low as 5 ng for TNT, 20 ng for DNT, and 5 ng for PA. In addition, experiments with normal production line explosives and their components show that this technology is also able to detect composition B, Pyrodex, and nitromethane. This method offers a convenient and sensitive method of detection of trace nitroaromatic explosive residue.     

Detection and Identification of Explosive Particles in Fingerprints Using Attenuated Total Reflection-Fourier Transform Infrared Spectromicroscopy

Abstract:  The application of attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectromicroscopy for detection of explosive particles in fingerprints is described. The combined functions of ATR-FTIR spectromicroscopy are visual searching of particles in fingerprints and measuring the FTIR spectra of the particles. These functions make it possible to directly identify whether a suspect has handled explosives from the fingerprints alone. Particles in explosive contaminated fingerprints are either ingredients of the explosives, finger residues, or other foreign materials. These cannot normally be discriminated by their morphology alone. ATR-FTIR spectra can provide both particle morphology and composition. Fingerprints analyzed by ATR-FTIR can be used for further analysis and identification because of its non-destructive character. Fingerprints contaminated with three different types of explosives, or potential explosives, have been analyzed herein. An infrared spectral library was searched in order to identify the explosive residues. The acquired spectra are compared to those of finger residue alone, in order to differentiate such residue from explosive residue.     

The discrimination of automotive clear coats by pyrolysis-gas chromatography/mass spectrometry and comparison of samples by a chromatogram library software

Identification particles used for the purpose of the post-blast identification of explosives have a coding system based on the combination of metal oxides and their various concentrations. These materials are composed of the polymeric matrix, iron powder (ferromagnetic properties), UV light active dyestuff and various metal oxides in a various ratios. A suitable analytical method has to be used for an accurate characterization of these metal components in the particles in order to find the required information, i.e. to determine the place and the year of production and as the case may be, also the production batch of misused explosives. In this work, the method of microwave digestion and flame atomic absorption spectrometry (F-AAS) was developed for an accurate determination of Zn, Mg, Cu and Pb in a few novel types of identification particles and applied to their characterization. When using specific sample treatment (digestion with a mixture of nitric acid with hydrochloric or hydrofluoric acid), the 3 sigma limits of detection (LODs) for the determination of Zn, Mg, Cu and Pb in 5mg original samples were 1.9, 0.2, 1.3 and 2.4 mg g(-1), respectively. The signal suppression due to the presence of HNO3+HCl or HNO3+HF was observed for Zn; therefore, the calibration solutions had to be prepared exactly with the same acids as those used for the sample mineralization. The determination of Mg, Cu and Pb was free of interferences; hence a simple calibration curve method could be adopted for attaining accurate results. The accuracy was checked by comparison of the results with those obtained by means of independent inductively coupled plasma optical emission spectrometry (ICP-OES). Good precision values, as relative standard deviation, in the range of 1-5% were obtained. A total number of 71 samples was analysed and classified by multivariate methods to prove the suitability of the procedure proposed for the purpose of the identification of explosives.     

Evaluation of Four Fingerprint Development Methods for Touch Chemistry Using Matrix‐Assisted Laser Desorption Ionization/Time‐of‐Flight Mass Spectrometry,

Four preparation techniques for MALDI/TOF mass spectrometry were compared to determine the ability to gather intelligence for investigations through the chemical analysis of latent fingerprints, defined as “touch chemistry.” Compatible fingerprint development processes used for identification along with new techniques are necessary to evaluate touch chemistry. Ten volunteers deposited fingerprints from solvent residues containing drugs and explosives onto microscope slides. The developers included (A) fingerprint powder, (B) MALDI matrix, (C) fingerprint powder and lifting, and (D) cyanoacrylate fuming with fingerprint powder. Qualitative identification was based on ion images and spectra. The highest average detection rates (88%) were found using methods A and B. Methods C (52%) or D (18%) had limited success. Results demonstrate the importance of imaging coupled to extracted mass spectral data in detecting analytes in deposited fingerprints. Overall, the results suggest continued development of touch chemistry applications could prove useful for gathering intelligence and forensically relevant information.     

Chemical fingerprinting of adhesive tapes by GCMS detection of petroleum hydrocarbon products

Pressure-sensitive adhesive tapes often represent key evidence of crimes such as assault, rape or homicide; thus, the development of analytical techniques able to contribute to a detailed characterization of these materials is of forensic importance. The gas chromatography-mass spectrometry (GCMS) analysis of the solvent extractable fractions of a suite of electrical and gaffer adhesive tapes spanning a range of colors and manufacturers identified a number of petroleum-derived hydrocarbons. Molecular and isotopic analyses of hydrocarbon constituents of complex materials have found wide analytical utility including the forensic investigation of oil spills and arson. Here, we investigate the utility of these techniques for characterizing the hydrocarbon composition of pressure-sensitive adhesive tapes for forensic correlation purposes. Subtle distinction of tape samples was evident in the GCMS distribution of several hydrocarbon groups including alkyl-naphthalenes, hopane and sterane biomarkers. Linear discriminant analysis of the abundances of these products provided high level differentiation of tape manufacturer. The distinction of different adhesive tape samples was further extended by measurement of their stable carbon isotopic values. The molecular and isotopic differences of the petroleum content of tapes are consistent with the use of different petroleum materials used in the manufacturing process and demonstrate the benefits of the combined use of complementary oil hydrocarbon characterization approaches. This study reveals the forensic potential of using established petroleum characterization methods for characterizing materials with a petroleum-derived hydrocarbon element.     

A Comparison of Common Swabbing Materials for the Recovery of Organic and Inorganic Explosive Residues

The efficiency of solvent based extraction methods used to remove explosive residues from four different swab types was investigated. Known amounts of organic and inorganic residues were spiked onto a swab surface with acetonitrile or ethanol:water combined with ultrasonication or physical manipulation used to extract the residues from each swab. The efficiency of each procedure was then calculated using liquid chromatography‐ultraviolet detection for organic residues and ion chromatography for inorganic residues. Results indicated that acetonitrile combined with physical agitation proved to be the most efficient method; returning analyte recoveries c. 95% for both alcohol based swabs and cotton balls. Inorganic residues were efficiently extracted using ethanol:water, while the use of acetonitrile followed by water significantly reduced the recovery of inorganic residues. Swab storage conditions were then investigated with results indicating decreased storage temperatures are required to retain the more volatile explosives.     

自制炸药包壳的爆炸规律研究

目的探讨同种材质的包壳受到不同量的炸药爆炸后的物理损坏程度及分布规律。方法采用相同材质包壳、不同质量的硝铵（密度0.6g/cm3）若干份进行实验,根据炸药质量和密闭塑料瓶包壳体积的比值（相对密度）建立横坐标,不同直径碎片质量为纵坐标做出工作曲线。结果在固定体积下的特定塑料包壳中,10g~30g硝铵炸药爆炸后,包壳碎片质量与炸药量存在一定的规律。结论本方法可用于推算一定范围内自制炸药爆炸的药量。     

Linking ammonium nitrate-aluminum (AN-AL) post-blast residues to pre-blast explosive materials using isotope ratio and trace elemental analysis for source attribution

Forensic science practitioners are often called upon to attribute crimes using trace evidence, such as explosive remnants, with the ultimate goal of associating a crime with a suspect or suspects in order to prevent further attacks. The explosive charge is an attractive component for attribution in crimes involving explosives as there are limited pathways for acquisition. However, there is currently no capability to link an explosive charge to its source via post-blast trace residues using isotope ratios or trace elements. Here, we sought to determine if pre-blast attribution signatures are preserved after detonation and can be subsequently recovered and detected. A field study was conducted to recover samples of post-blast explosives from controlled detonations of ammonium nitrate-aluminum (AN-Al), which were then analyzed via isotope ratio mass spectrometry (IRMS) and inductively coupled plasma-mass spectrometry (ICP-MS) for quantitation and profiling of isotopes ratio and trace element signatures, respectively. Oxygen and nitrogen isotope ratios from AN-Al yielded some of the most promising results with considerable overlap within one standard deviation of the reference between the spreads of pre- and post-blast data. Trace element results from AN-Al support the findings in the isotope ratio data, with 26 elements detected in both pre- and post-blast samples, and several elements including B, Cd, Cr, Ni, Sn, V, and Zn showing considerable overlap. These preliminary results provide a proof-of-concept for the development of forensic examinations that can attribute signatures from post-blast debris to signatures in pre-blast explosive materials for use in future investigations.     

苯二氮卓类新精神活性物质去氯依替唑仑的定性检验方法研究

目的建立苯二氮卓类新精神活性物质去氯依替唑仑的气相色谱-质谱(GC-MS)和超高效液相色谱-四极杆-飞行时间质谱(UPLC-Q-TOF MS)定性检验方法。方法未知样品用甲醇和水提取,取上清液,采用GC-MS和UPLC-Q-TOF MS进行分析。结果经GC-MS检测,保留时间为17.73 min的未知组分的质谱碎片主要特征离子峰有m/z 279,308,239,252,225,77,126。经UPLC-Q-TOF MS检测,保留时间为4.781 min的未知组分的准分子离子峰为309.1173,碰撞诱导解离(CID)模式下二级质谱主要离子有m/z 280.0776,255.0952,240.0719,225.0604,206.0748。经缴获毒品分析科学工作组(Scientific Working Group for the Analysis of Seized Drugs,SWGDRUG)分析谱库检索和文献查询获得的信息资料进行比对,鉴定为去氯依替唑仑。结论该方法具有分析简便、快速的特点,可以用于实际案件的检测。     

Evaluation of canine training aids containment for homemade explosive and components by headspace analysis and canine testing

While canines are most commonly trained to detect traditional explosives, such as nitroaromatics and smokeless powders, homemade explosives (HMEs), such as fuel–oxidizer mixtures, are arguably a greater threat. As such, it is imperative that canines are sufficiently trained in the detection of such HMEs. The training aid delivery device (TADD) is a primary containment device that has been used to house HMEs and HME components for canine detection training purposes. This research assesses the odor release from HME components, ammonium nitrate (AN), urea nitrate (UN), and potassium chlorate (PC), housed in TADDs. Canine odor recognition tests (ORTs) were used with analytical data to determine the detectability of TADDs containing AN, UN, or PC. Headspace analysis by gas chromatography/mass spectrometry (GC/MS) with solid-phase microextraction (SPME) or online cryotrapping were used to measure ammonia or chlorine, as well as other unwanted odorants, emanating from bulk AN, UN, and PC in TADDs over 28 weeks. The analytical data showed variation in the amount of ammonia and chlorine over time, with ammonia from AN and UN decreasing slowly over time and the abundance of chlorine from PC TADDs dependent on the frequency of exposure to ambient air. Even with these variations in odor abundance, canines previously trained to detect bulk explosive HME components were able to detect all three targets in glass and plastic TADDs for at least 18 months after loading. Detection proficiency ranged from 64% to 100% and was not found to be dependent on either age of material.     

Application of spectral libraries for characterization of oxidizers in post-blast residues by electrospray mass spectrometry

The goal of this paper is to demonstrate that electrospray mass spectrometry when used with spectral libraries becomes a useful method for rapid identification of inorganic oxidizers commonly present in commercial and improvised explosives. Electrospray ionization mass spectra (ESI-MS) of oxidizers reveal a series of characteristic cluster ions. Such a set of cluster ions can be regarded as a "fingerprint" of a particular oxidizer. With the aid of a spectral library, tentative identification of inorganic oxidizer becomes automated and an easy-to-implement process. The oxidizer identity may be further confirmed by using tandem mass spectrometry (MS/MS). Because it is not necessary to separate the components before analysis, results become available in real time. Little sample consumption and the ease of sample preparation should also be noted. The methodology can be readily employed on various ESI-MS systems that are already in use in analytical laboratories. This is another important benefit as the ESI-MS instrumentation is becoming increasingly common in forensic laboratories.     

Determination of elemental sulfur in explosives and explosive residues by gas chromatography-mass spectrometry

A new method for the positive identification of elemental sulfur in explosives and explosive residues is developed. Following a carbon disulfide wash of explosives or explosive residues, a sample of the extracted material is injected onto a gas chromatography (GC) column, then analyzed via mass-selective (MS) detection. A positive identification of elemental sulfur is based on both retention time and fragmentation pattern. The GC-MS method is demonstrated to be useful in detecting and positively identifying elemental sulfur from both burned and unburned explosive mixtures. With a detection limit of 2.5 ng (2.5 x 10(-9) grams) of elemental sulfur on the column, it is shown to be 400 times more sensitive than the presumptive chemical color test that is currently the method employed for detection of small amounts of sulfur.     

爆炸物犯罪司法疑难问题及其解决

爆炸物犯罪的法律规定存在漏洞,刑法理论界对有关爆炸物犯罪的研究欠深、广,导致了司法实践中处理爆炸物犯罪时对犯罪对象、行为、罪数认定及刑罚裁量等出现争议和疑难。认真探讨这些问题,对丰富爆炸物犯罪理论和解决爆炸物犯罪量刑失衡具有重大意义。立法和司法解释对爆炸物的外延不周延,应从社会危害性角度考虑予以解决;对爆炸物犯罪行为认定的疑难,应从各种犯罪行为的本质特点予以认定;对罪数形态认定的疑难,应从把握事后不可罚行为和想象竞合犯等刑法理论的基础上具体分析认定;对于刑罚裁量上的失衡,应从正确认定处罚情节和正确适用司法解释来解决。     

拉曼光谱法鉴别常见炸药

目的建立一种识别炸药的方法。方法使用激光显微拉曼光谱法对17种常见炸药粉末进行了分析。结果17种常见炸药均有丰富的拉曼位移峰,可以通过其位移峰峰位的不同区分不同成分的炸药。结论拉曼光谱法适用于快速准确地识别炸药。     

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. In order to compare mimic materials to their explosive counterparts, a technique must be established that not only allows for identification of volatile compounds but also can monitor changes in the headspace profile over time with respect to time and temperature. The Automated Training Aid Simulation using SPME (or ATASS) was developed for that purpose. As described, ATASS was used to observe changes in the volatile profile of three explosives (Composition C-4, 2,4-dinitrotoluene (DNT), and triacetone triperoxide (TATP)) and respective prototype training materials (0.1% by mass C-4, 1% by mass 2,4-DNT, and 1% by mass TATP). Samples were prepared in vials and metal tins within a gallon (≈ 3785 mL) paint can to simulate common field techniques for canine training. Monitoring these materials in real time provides a better understanding of the major volatile components present and how the relative abundances of these components can change over time. The results presented indicate that ATASS successfully allows for a sufficient comparison between explosive and non-explosive training materials.     

Comparison of motor oils using high-temperature gas chromatography-mass spectrometry

The analysis of motor oils has wide applications in the forensic science field from comparing lubricants transferred between an automobile and a victim or crime scene to differentiating the compositions of plastic explosives. In this study, 40 unused motor oils were analyzed and compared by high-temperature gas chromatography-mass spectrometry to determine the potential for oil individualization. Oil samples were also collected from the crankcase dipsticks of 30 cars. Twenty-six of these oils could be differentiated from each other based on visual comparisons of the unresolved envelope (baseline rise due to incomplete separation) and the resolved hydrocarbons in the raw total ion chromatograms (TICs) and smoothed TIC data. Four of these oils were analyzed as unknowns and were correctly related to the corresponding vehicle. The use of extracted ion profiles (EIPs) was explored as a means to further discriminate between the indistinct samples based on the polycyclic aromatic hydrocarbon (PAH) content. The research discussed in this paper demonstrated that differentiation of motor oils was possible by examining the TIC, smoothed TIC, and EIP data.     

Liquid chromatography-mass spectrometric and liquid chromatography-tandem mass spectrometric determination of hallucinogenic indoles psilocin and psilocybin in "magic mushroom" samples

Accurate and sensitive analytical methods for psilocin (PC) and psilocybin (PB), tryptamine-type hallucinogens contained in "magic mushrooms," were investigated using liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS-MS). The chromatographic separation on an ODS column and mass spectral information gave complete discrimination between PC and PB without derivatization. The mass spectrometric detection had a high sensitivity, and the tandem mass spectrometric detection provided more specificity and accuracy, as well as high sensitivity. The detection limits ranged from 1 to 25 pg by LC-MS in the selected ion monitoring mode, and the intra- and inter-day coefficients of variation were estimated to be 4.21-5.93% by LC-MS-MS in the selected reaction monitoring mode. By applying the present LC-MS-MS technique to four real samples, the contents of PC and PB were found to vary over a wide range (0.60-1.4 and 0.18-3.8 mg/g dry wt. for PC and PB, respectively) between samples.     

Solid phase micro extraction coupled with on-column GC/ECD for the post-blast analysis of organic explosives

Gas chromatographic analysis with electron capture detection is very sensitive to post-blast residues and useful for the determination of organic explosive molecules. But many compounds extracted from the matrices may interfere with the explosives. Using SPME, most interfering compounds are eliminated so the identification is easier. Another advantage of the technique is a low limit of detection. In this study, four different SPME fibers were tested to analyze the most common encountered organic explosives including nitro aromatics, nitramines and nitro-esters. Different parameters were tested (desorption time, agitation, ...) and a special device has been created to optimize the agitation. Direct desorption effect of the SPME fiber on the column compared to normal split-splitless injection is shown. In this way, the degradation of the most sensitive molecules is decreased. An application to a real case is also described in this paper.