Highly sensitive screening method for nitroaromatic, nitramine and nitrate ester explosives by high performance liquid chromatography-atmospheric pressure ionization-mass spectrometry (HPLC-API-MS) in forensic applications

A highly sensitive screening method based on high performance liquid chromatography atmospheric pressure ionization mass spectrometry (HPLC-API-MS) has been developed for the analysis of 21 nitroaromatic, nitramine and nitrate ester explosives, which include the explosives most commonly encountered in forensic science. Two atmospheric pressure ionization (API) methods, atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), and various experimental conditions have been applied to allow for the detection of all 21 explosive compounds. The limit of detection (LOD) in the full-scan mode has been found to be 0.012-1.2 ng on column for the screening of most explosives investigated. For nitrobenzene, an LOD of 10 ng was found with the APCI method in the negative mode. Although the detection of nitrobenzene, 2-, 3-, and 4-nitrotoluene is hindered by the difficult ionization of these compounds, we have found that by forming an adduct with glycine, LOD values in the range of 3-16 ng on column can be achieved. Compared with previous screening methods with thermospray ionization, the API method has distinct advantages, including simplicity and stability of the method applied, an extended screening range and a low detection limit for the explosives studied.     

A second survey of high explosives traces in public places

This survey was carried out as a follow-up to a 1994 survey carried out by this laboratory (1) in order to determine the background levels of explosives traces in public places. The first survey concentrated on transport areas and police stations in and around London. This second study examines levels in four of the United Kingdom's major cities: Birmingham, Cardiff, Glasgow, and Manchester. Samples were taken at various transport sites and from hotels, private houses, private vehicles, and clothing. The survey showed that traces of the high explosives nitroglycerine (NG), trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), and cyclotrimethylene trinitramine (RDX) are rare within the general public environment. Only one low-level trace of RDX was detected. NG, possibly associated with the use of firearms, was detected at low levels in two samples and 2,4-DNT was detected in a separate sample. No PETN was detected in any of the samples. The results of the survey indicate that it is unlikely that persons visiting public areas could become significantly contaminated with explosives. The analytical procedures employed would also have detected ethylene glycol dinitrate (EGDN) if present at levels greater than 2 ng, nitrobenzene (NB) if present at levels greater than 50 ng, mononitrotoluenes if present at levels greater than 50 ng, and the other common isomers of dinitrotoluene if these had been present at levels in excess of 10 ng. None of these were detected. The relatively high volatility of EGDN, NB, and the mononitrotoluenes would, however, cause traces of these compounds to disperse rapidly. A proportion of the samples (approximately 7%) were analyzed for the presence of HMX. No HMX was detected.     

X射线衍射法检验有机炸药初探

目的 建立X射线衍射法（XRD）检验有机炸药的方法.方法 使用X射线衍射仪对有机炸药苦味酸（PA）,太安（PTEN）,黑索金（RDX）,梯恩梯（TNT）进行测试分析.结果 准确测定出有机炸药的物质组成及结构.结论 该方法能够直接给出有机炸药的分子式及结构组成,定性准确,操作简便,可用于有机炸药的定性检测.     

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.     

Optimization of Headspace Solid‐Phase Microextraction Technique for Extraction of Volatile Smokeless Powder Compounds in Forensic Applications

Smokeless powders are low explosives and are potentially found in cases involving firearms and improvised explosive devices. Apart from inorganic compound analysis, forensic determination of organic components of these materials appears as a promising alternative, especially the chromatographic techniques. This work describes the optimization of a solid‐phase microextraction technique using an 85 μm polyacrylate fiber followed by gas chromatography‐flame ionization detection for smokeless powder. A multivariate experimental design was performed to optimize extraction‐influencing parameters. A 2⁴ factorial first‐order design revealed that sample temperature and extraction time were the major influencing parameters. Doehlert matrix design has subsequently selected 66°C and 21 min as the compromised conditions for the two predetermined parameters. This extraction technique has successfully detected the headspace compounds of smokeless powders from different ammunition types and allowed for their differentiation. The novel technique allows more rapid sample preparation for chromatographic detection of smokeless powders.     

Rapid Quantitative Analysis of Multiple Explosive Compound Classes on a Single Instrument via Flow‐Injection Analysis Tandem Mass Spectrometry

A flow‐injection analysis tandem mass spectrometry (FIA MSMS) method was developed for rapid quantitative analysis of 10 different inorganic and organic explosives. Performance is optimized by tailoring the ionization method (APCI/ESI), de‐clustering potentials, and collision energies for each specific analyte. In doing so, a single instrument can be used to detect urea nitrate, potassium chlorate, 2,4,6‐trinitrotoluene, 2,4,6‐trinitrophenylmethylnitramine, triacetone triperoxide, hexamethylene triperoxide diamine, pentaerythritol tetranitrate, 1,3,5‐trinitroperhydro‐1,3,5‐triazine, nitroglycerin, and octohy‐dro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine with sensitivities all in the picogram per milliliter range. In conclusion, FIA APCI/ESI MSMS is a fast (<1 min/sample), sensitive (~pg/mL LOQ), and precise (intraday RSD < 10%) method for trace explosive detection that can play an important role in criminal and attributional forensics, counterterrorism, and environmental protection areas, and has the potential to augment or replace several of the existing explosive detection methods.     

The analysis of quaternary ammonium compounds in human urine by direct inlet electron impact ionization mass spectrometry.

An accurate and rapid screening test for nine quaternary ammonium compounds (suxamethonium chloride, pancuronium bromide, ambenonium chloride, benzethonium chloride, distigmine bromide, methylbenactyzium bromide, neostigmine bromide, propantheline bromide and pyridostigmine bromide) by direct inlet electron impact ionization mass spectrometry (DI/EI-MS) was investigated. Each compound was extracted from urine as an ion pair with KI3 into dichloromethane. The reliability of the identification of these compounds was verified by the mass chromatographic analysis of their characteristic fragment ions. The analysis of these drugs by DI/EI-MS could be performed within 5 min. The detection limits were between 20-150 ng/ml for the nine compounds. This method appears to be efficient, rapid and suitable as a screening procedure for the quaternary ammonium compounds found in urine.     

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.     

Detection of nitro-organic and peroxide explosives in latent fingermarks by DART- and SALDI-TOF-mass spectrometry

The ability of two mass spectrometric methods, surface-assisted laser desorption/ionization-time of flight-mass spectrometry (SALDI-TOF-MS) and direct analysis in real time (DART-MS), to detect the presence of seven common explosives (six nitro-organic- and one peroxide-type) in spiked latent fingermarks has been examined. It was found that each explosive could be detected with nanogram sensitivity for marks resulting from direct finger contact with a glass probe by DART-MS or onto stainless steel target plates using SALDI-TOF-MS for marks pre-dusted with one type of commercial black magnetic powder. These explosives also could be detected in latent marks lifted from six common surfaces (paper, plastic bag, metal drinks can, wood laminate, adhesive tape and white ceramic tile) whereas no explosive could be detected in equivalent pre-dusted marks on the surface of a commercial lifting tape by the DART-MS method due to high background interference from the tape material. The presence of TNT and Tetryl could be detected in pre-dusted latent fingermarks on a commercial lifting tape for up to 29 days sealed and stored under ambient conditions.     

Rapid quantitative colourimetric tests for trinitrotoluene (TNT) in soil

A rapid quantitative colourimetric test was developed for the determination of 2,4,6-Trinitrotoluene (TNT) in soil. Quantification was achieved using an innovative application of photography where the relationship between the Red Green Blue (RGB) value and concentration of colorimetric product was exploited. The wide linear range (1-50mg/L) and low detection limit (0.73±0.01mg/L to 3.5±0.4mg/L) achieved was comparable with spectrophotometric quantification methods. Quantification was validated both with known concentration standards and spiked soil extracts confirming the accuracy of the technique. The results demonstrate a powerful technique with the capacity for development as a rapid on site field test for the analysis of explosives.     

Conditioned Microplitis croceipes Cresson (Hymenoptera: Braconidae) detect and respond to 2,4-DNT: development of a biological sensor

We examined the ability of M. croceipes to learn, detect, and respond to 2,4-DNT, which is a volatile discriminator of trinitrotoluene (TNT). The percentage of conditioned wasps to detect and respond to the various concentrations of 2,4-DNT for > or = 15 sec was measured. Significantly more of the conditioned wasps responded to the concentration of 2,4-DNT used for conditioning than other concentrations examined. Accordingly, percent conditioned wasps to respond > or = 15 sec could be used as a suitable measure to screen air samples and distinguish between samples with or without the target odorant. The data recorded in this study indicate the measured behavior could be used to estimate the concentration of target odorants. Data in this study indicate M. croceipes can detect and respond to this compound, which provide further support for its development as a biological sensor.     

An Accelerated Analytical Process for the Development of STR Profiles for Casework Samples

Significant efforts are being devoted to the development of methods enabling rapid generation of short tandem repeat (STR) profiles in order to reduce turnaround times for the delivery of human identification results from biological evidence. Some of the proposed solutions are still costly and low throughput. This study describes the optimization of an analytical process enabling the generation of complete STR profiles (single‐source or mixed profiles) for human identification in approximately 5 h. This accelerated process uses currently available reagents and standard laboratory equipment. It includes a 30‐min lysis step, a 27‐min DNA extraction using the Promega Maxwell^®16 System, DNA quantification in <1 h using the Qiagen Investigator^® Quantiplex HYres kit, fast amplification (<26 min) of the loci included in AmpF?STR^® Identifiler^®, and analysis of the profiles on the 3500‐series Genetic Analyzer. This combination of fast individual steps produces high‐quality profiling results and offers a cost‐effective alternative approach to rapid DNA analysis.     

Development and validation of highly selective screening and confirmatory methods for the qualitative forensic analysis of organic explosive compounds with high performance liquid chromatography coupled with (photodiode array and) LTQ ion trap/Orbitrap mass spectrometric detections (HPLC-(PDA)-LTQOrbitrap)

An LTQ-Orbitrap FTMS is a new (hybrid) mass spectrometric (MS) analyzer. It allows for the acquisition of full scan MSⁿ (n-stage fragmentations, n = 1 − n) spectra with the linear ion trap detector (LTQ) at high speed and/or with the Fourier Transform-detector (Orbitrap) with ultra high mass resolution (> 60,000 at m/z < 400 amu) and high mass accuracy (≤ 1 ppm with internal calibration). In addition it may be coupled with liquid chromatography (LC) with photo diode array (PDA) detection.Two methods for the forensic screening and confirmation of all common trace explosives in post-blast residues have been developed on this instrument using atmospheric pressure chemical ionization (APCI). In one run, the nitrogen-containing explosives are analyzed with the combination of “LC-(PDA)-APCI(−)-LTQ MS²/Orbitrap FTMS” (Method 1). In another run, peroxide explosives are analyzed with “LC-APCI(+)-LTQ MS²/Orbitrap FTMS” (Method 2).The performance of both methods has been validated according to procedures defined in the EU COMMISSION DECISION implementing Council Directive 96/23/EC concerning the performance of analytical methods and the interpretation of results (DC 2002/657/EC) and other standards (NEN 17025 and NEN 7777). The methods are highly selective due to the simultaneous utilization of the Orbitrap FTMS and LTQ MS², both of which are highly selective detectors Tested explosive compounds can be detected in the molecular ion form by the Orbitrap analyzer with minimal mass interference in different matrices when using an extremely narrow mass tolerance detection window (≤ 2 ppm). The identification of a detected compound follows an identification point system. Experimental results show that almost all explosive compounds meet the confirmation criteria (minimum 4 points) required for the positive identification by the DC 2002/657/EC.     

New developments in SPME Part 2: Analysis of ammonium nitrate-based explosives

Solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) is a simple, reliable technique for the recovery and analysis of many organic explosives. However, this technique is impractical for the analysis of ammonium nitrate-type explosives due to the extreme polarity, low molecular weight, and high volatility of the amine moiety. This article describes an initial investigation of a derivatization process utilizing alkylchloroformates that converts ammonium nitrate and methylammonium nitrate into a form suitable for recovery by SPME and analysis by GC-MS.     

Novel technique for the combined recovery, extraction and clean-up of forensic organic and inorganic trace explosives samples.

This paper describes a simple processing and analysis scheme for explosives trace swab samples which deals both with organic and inorganic materials. Swabs, wetted with ethanol or ethanol/water mixture, were extracted with ethanol/water mixture. The extract was passed directly through a simple column containing an acrylonitrile/styrene copolymer adsorbent. The adsorbent retained common organic explosives, which were recovered with an efficiency of 30-50% as a relatively clean ethyl acetate solution. The concentrated ethyl acetate eluate was analysed using gas chromatography with chemiluminescence or mass spectrometric detection. The unretained inorganic ions and sugars, which were recovered with generally high efficiency as an ethanol/water solution, could be directly analysed using ion chromatography and/or capillary electrophoresis. Minor difficulties encountered in the analysis of sugars, fluoride and phosphate were examined.     

Detection limits for GC/MS analysis of organic explosives

Method detection limits are determined and compared for analysis of liquid injections of organic explosives and related compounds by gas chromatography-mass spectroscopy utilizing electron impact (EI), negative ion chemical ionization (NICI), and positive ion chemical ionization (PICI) detection methods. Detection limits were rigorously determined for a series of dinitrotoluenes, trinitrotoluene, two nitroester explosives, and one nitramine explosive. The detection limits are lower by NICI than by EI or PICI for all explosives examined, with the exception of RDX. The lowest detection limit for RDX was achieved in the PICI ionization mode. Judicious choice of the appropriate ionization mode can enhance selectivity and significantly lower detection limits. Major ions are reported for each analyte in EI, PICI, and NICI detection modes.     

Accumulation of explosives in hair--part II: factors affecting sorption

This study examines the sorption of eight explosives (2,4,6-trinitrotoluene [TNT]; pentaerythritol tetranitrate [PETN]; hexahydro-1,3,5-trinitro-s-triazine [RDX]; diacetone diperoxide [DADP]; triacetone triperoxide [TATP]; ethylene glycol [EGDN], nitroglycerin [NG]; and 2,4-dinitrotoluene [DNT]) to human hair. The study uses only cut hair, which is exposed to explosive vapor. The vapor transfer studies reported herein indicated that hair did not reach saturation even after 2.5 years of exposure to TNT. While previous studies showed black hair sorbed more explosive than blond or brown, this study reports that red hair sorption is similar to black, while grey hairs, exposed along with black hair from the same individual, sorbed significantly less explosive than the same individual's black hairs. In a study using only black hair, a slight racial bias was observed with sorption greater for Mongoloid hair as compared to Caucasian or Negroid. Only for Mongoloid hairs were enough samples studied to examine for a gender bias, but one was not observed. There was much variability in results in all categories (hair color, race, and gender) that trends were established only in general terms. Hair at different ages was tested for a few individuals. Detailed studies focused on the sorption of TATP and TNT as these appear to be sorbed most differently-TATP mainly on the hair surface and TNT both on the surface and in the cortex. The uptake of high vapor pressure explosives (e.g., TATP) and moderate vapor pressure explosives (e.g., TNT) by hair was rapid and could be detected within about 1 h of exposure. Both explosives were readily sorbed by pure melanin.     

Analysis of hydrogen peroxide field samples by HPLC/FD and HPLC/ED in DC mode

The goal of this paper is to describe applications of two recently developed HPLC methods for the analysis and confirmation of the presence of hydrogen peroxide residues in field studies. The procedure utilizes two different HPLC systems, one with post-column derivatization followed by fluorescence detection (HPLC/FD), and the other with electrochemical detection (HPLC/ED). The two systems were utilized to detect hydrogen peroxide in a variety of typical forensic samples including pre- and post-blast samples, as well as a series of environmental control samples. Peroxide-based organic explosives were also examined due to their propensity to produce peroxide residues following detonation. Because samples collected from post-blast scenes are frequently shipped or stored prior to analysis, the effects of storage time, temperature and type of substrate material on the recovery of hydrogen peroxide residues were also investigated. The combined results of the study demonstrate the capability of two HPLC approaches with selective detection in the analysis and investigation of suspected incidents involving peroxide based explosives.     

纸喷雾质谱在物证检验中的应用

物证检验中,建立简便、快捷、样品前处理步骤少的质谱分析方法一直是一大挑战。纸喷雾电离技术具有快速灵敏、经济高效、操作简便的特点,可有效解决物证检验中的难题。本文综述了纸喷雾电离质谱在物证检验领域相关应用的最新进展,主要包括毒物毒品分析、药物滥用、农残检测、食品及日用品安全、文书检验及爆炸物检测,并辅以展望。