Detection of explosives and their degradation products in soil environments

Polynitro organic explosives [hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 2,4,6-trinitrotoluene (TNT)] are typical labile environmental pollutants that can biotransform with soil indigenous microorganisms, photodegrade by sunlight and migrate through subsurface soil to cause groundwater contamination. To be able to determine the type and concentration of explosives and their (bio)transformation products in different soil environments, a comprehensive analytical methodology of sample preparation, separation and detection is thus required. The present paper describes the use of supercritical carbon dioxide (SC-CO2), acetonitrile (MeCN) (US Environmental Protection Agency Method 8330) and solid-phase microextraction (SPME) for the extraction of explosives and their degradation products from various water, soil and plant tissue samples for subsequent analysis by either HPLC-UV, capillary electrophoresis (CE-UV) or GC-MS. Contaminated surface and subsurface soil and groundwater were collected from either a TNT manufacturing facility or an anti-tank firing range. Plant tissue samples were taken fromplants grown in anti-tank firing range soil in a greenhouse experiment. All tested soil and groundwater samples from the former TNT manufacturing plant were found to contain TNT and some of its amino reduced and partially denitrated products. Their concentrations as determined by SPME-GC-MS and LC-UV depended on the location of sampling at the site. In the case of plant tissues, SC-CO2 extraction followed by CE-UV analysis showed only the presence of HMX. The concentrations of HMX (<200 mg/kg) as determined by supercritical fluid extraction (SC-CO2)-CE-UV were comparable to those obtained by MeCN extraction, although the latter technique was found to be more efficient at higher concentrations (>300 mg/kg). Modifiers such as MeCN and water enhanced the SC-CO2 extractability of HMX from plant tissues.     

Direct mass spectrometric detection of trace explosives in soil samples

The detection of explosives in soil is of great significance in public security programmes and environmental science. In the present work, a ppb-level method was established to directly detect the semi-volatile explosives, RDX and TNT, present in complex soil samples. The method used thermal sampling technique and a direct current atmospheric pressure glow discharge source mounted with a brass cylinder electrode (9 mm × 4.6 mm i.d./5.6 mm o.d.) to face the samples, requiring no sample pretreatment steps such as soil extraction (about ten hours). It was characterized by the merits of easy operation, high sensitivity and fast speed, and has been validated by real soil samples from various locations around a factory or firecracker releasing fields. It took only 5 min per sample, with the limit of detection down to 0.5 ppb (S/N = 3) trinitrohexahydro-1,3,5-triazine in soils heated at 170 °C. It is also extendable to the analysis of other volatile analytes.     

Analysis of CL-20 in environmental matrices: water and soil

Analytical techniques for the detection of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo(5.5.0.05,9.03,11)dodecane (CL-20) in water and soil are developed by adapting methods traditionally used for the analysis of nitroaromatics. CL-20 (a new explosives compound) is thermally labile, exhibits high polarity, and has low solubility in water. These constraints make the use of specialized sample handling, preparation, extraction, and analysis necessary. The ability to determine the concentrations of this new explosive compound in environmental matrices is helpful in understanding the environmental fate and effects of CL-20; understanding the physical, chemical, and biological fate of CL-20; and can be used in developing remediation technologies and determining their efficiency. The toxicity and mobility of new explosives in soil and groundwater are also of interest, and analytical techniques for quantitating CL-20 and its degradation products in soil and natural waters make these investigations possible.     

A platform for on-site environmental analysis of explosives using high performance liquid chromatography with UV absorbance and photo-assisted electrochemical detection

High-performance liquid chromatography with photo-assisted electrochemical detection (HPLC-PAED) is used in conjunction with ultraviolet absorbance (UV) detection for determining explosives in environmental samples. The system utilizes an on-line solid-phase extraction technique for sample pretreatment (i.e., fractionation and concentration), thus reducing the required ground water sample size from 1 L to 2 mL and minimizing sample handling. Limits of detection for explosives using solid-phase extraction and PAED range from 0.0007 to 0.4 μg/L, well below those achieved with UV detection for several important explosives (e.g., RDX). The method has demonstrated good accuracy, precision, and recovery for all tested explosives, thus proving that the method is suitable for evaluation of explosives in ground water with competitive advantages over the U.S. Environmental Protection Agency (EPA) Method 8330. A system adaptable for the on-site environmental analysis of explosives has been developed and validated.     

Fast analysis of high-energy compounds and agricultural chemicals in water with desorption electrospray ionization mass spectrometry

Novel sampling and detection methods using desorption electrospray ionization (DESI) are examined in the detection of explosives (RDX, TNT, HMX, and TNB) and agricultural chemicals (atrazine, alachlor and acetochlor) from aqueous matrices and authentic contaminated groundwater samples. DESI allows analysis of solid and liquid compounds directly from surfaces of interest with little or no sample preparation. Significant savings in analysis time and sample preparation are realized. The methods investigated here include (i) immediate analysis of filter paper wetted with contaminated water samples without further sample preparation, (ii) rapid liquid-liquid extraction (LLE), and (iii) analyte extraction from contaminated groundwater samples on-site using solid-phase extraction (SPE) membranes, followed by direct DESI analysis of the membrane. The wetted filter paper experiment demonstrates the maximum sample throughput for DESI analysis of aqueous matrices but has inadequate sensitivity for some of these analytes. Both the LLE and the SPE methods have adequate sensitivity. The resulting SPE membranes and/or small volume solvent extracts produced in these experiments are readily transported to off-site facilities for direct analysis by DESI. This realizes a significant reduction in the costs of sample shipping compared with those for typical liter-sized samples of groundwater. Total analysis times for these preliminary DESI analyses are comparable with or shorter than those for GC/MS and limits of detection approach environmental action levels for these compounds while maintaining a modest relative standard deviation. Tandem mass spectrometric data is used to provide additional specificity as needed.     

Non-aerosol detection of explosives with a continuous flow immunosensor

Contamination of groundwater, soil, and the marine environment by explosives is a global issue. Identification, characterization and remediation are all required for a site recognized as contaminated with 2,4,6-trinitrotoluene (TNT) or hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). For each step, a method to accurately measure the contaminant level is needed. This paper reviews some of the current methods with emphasis on a single biosensor developed in our laboratory. Current regulatory methods require samples to be sent off-site to a certified laboratory resulting in time delays up to a month. A continuous flow biosensor for detection of explosives has been developed and tested for the rapid field screening of environmental samples. The detection system is based on a displacement immunoassay in which monoclonal antibodies to (TNT) and RDX are immobilized on solid substrates, allowed to bind fluorescently labeled antigens, and then exposed to explosives in aqueous samples. Explosive compounds present in the sample displace proportional amounts of the fluorescent label, which can then be measured to determine the original TNT or RDX concentration. The system can accurately detect ppb to ppt levels of explosives in groundwater or seawater samples and in extracts of contaminated soil. The biosensor has applications in environmental monitoring at remediation sites or in the location of underwater unexploded ordnance.     

Analysis of Explosives in Soil Using Solid Phase Microextraction and Gas Chromatography

Abstract

Current methods for the analysis of explosives in soils utilize time consuming sample preparation workups and extractions. The method detection limits for EPA Method 8330 for most analytes is substantially higher than the typical explosive concentrations encountered in soils near unexploded ordnance items, landmines, or other hidden explosive devices. It is desirable to develop new analytical techniques to analyze soil with low concentrations of explosives to support the development of explosive sensors. This report describes efforts to adapt headspace solid phase extraction and gas chromatography/mass spectrometry to provide a convenient and sensitive analysis method for explosives in soil.     

A critical review of vacuum-assisted headspace solid-phase microextraction for environmental analysis

Vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) is an emerging analytical technique, which further advances HSSPME by providing lower detection limits of analytes with poor volatility at shorter extraction times. This review discusses the theoretical aspects and possibilities of the Vac-HSSPME technique for analysis of environmental samples. Optimization of key parameters, currently available equipment and methods for quantification of organic pollutants in water and soil are considered. Key problems and limitations of the technique are discussed along with possible approaches for its future development. The technique has a well-developed theory, which could be used for modeling of the extraction process, faster method development, and optimization. Wider application of the technique is limited by the lack of automation, which, however, seems possible to develop and implement by manufacturers of commercial multi-purpose autosamplers for gas chromatography instruments. It has been shown that Vac-HSSPME allows decreasing cross-contamination of samples from the laboratory air, which is advantageous for identification and quantification of trace environmental pollutants. Simple equipment for the technique makes it possible to apply for on-site sample preparation and analysis of environmental samples.     

Extraction and clean-up strategies for the analysis of poly- and perfluoroalkyl substances in environmental and human matrices

The rapidly expanding field of per- and polyfluorinated alkyl substances (PFASs) research has resulted in a wide range of analytical methodologies to determine the human and environmental exposure to PFASs. This paper reviews the currently applied techniques for sample pre-treatment, extraction and clean-up for the analysis of ionic and non-ionic PFASs in human and environmental matrices. Solid phase extraction (SPE) is the method of choice for liquid samples (e.g. water, blood, serum, plasma), and may be automated in an on-line set-up for (large volume) sample enrichment and sample clean-up. Prior to SPE, sample pre-treatment (filtration or centrifugation for water or protein precipitation for blood) may be required. Liquid-liquid extraction can also be used for liquid samples (and does not require above mentioned sample pretreatment). Solid-liquid extraction is the commonly applied method for solid matrices (biota, sludge, soil, sediment), but automation options are limited due to contamination from polytetrafluorethylene tubings and parts applied in extraction equipment. Air is generally preconcentrated on XAD-resins sandwiched between polyurethane foam plugs. Clean-up of crude extracts is essential for destruction and removal of lipids and other co-extractives that may interfere in the instrumental determination. SPE, (fluorous) silica column chromatography, dispersive graphitized carbon and destructive methods such as sulphuric acid or KOH treatment can be applied for clean-up of extracts. Care should be taken to avoid contamination (e.g. from sample bottles, filters, equipment) and losses of PFASs (e.g. adsorption, volatilization) during sampling, extraction and clean-up. Storage at -20 degrees C is generally appropriate for conservation of samples.     

On-matrix derivatisation-extraction of precursors of nitrogen- and sulfur-mustards for verification of chemical weapons convention

Development and refinement of sample preparation protocols for retrospective detection and identification of chemical warfare agents (CWAs) and their markers is of paramount importance from verification point of view of chemical weapons convention (CWC). Precursors of nitrogen- and sulfur-mustards (NMPs and SMPs) are polar adsorptive markers of vesicant class of CWAs. Their detection in a given environmental sample may imply past contamination with mustards. For the efficient extraction of NMPs and SMPs from soil, on-matrix derivatisation-extraction (OMDEX) method was developed and optimized. The method involved trifluoroacetylation of analytes on soil itself, followed by extraction with suitable solvent. The extracted samples were analyzed by gas chromatography-mass spectrometry (GC-MS). This virtually single-step sample preparation offered better recoveries of NMPs and SMPs in comparison to conventionally used extraction, evaporation and derivatisation. The best recoveries of analytes were obtained with acetonitrile by OMDEX method. Dynamic linearity range of trifluoroacetylated (TFA) derivatives of NMPs and SMPs was 1-12 microg/L in GC-MS analysis in SIM mode. Repeatability and reproducibility of this technique containing 5 and 10 microg analytes/gm soil was <3.3% and <4.6%, respectively. OMDEX technique was finally applied for the detection of TFA derivatives of NMPs in the soil sample supplied in 16th official proficiency test conducted by OPCW in October 2004.     

The USACHPPM gas chromatographic procedures for the analysis of waters and soils for energetics and related compounds

The procedures currently used by the U.S. Army Center for Health Promotion and Preventive Medicine (USACHPPM) for the analysis of energetics and related compounds in water and soils are presented. These procedures are based on the use of isoamyl acetate to extract the analytes of interest from their environmental matrices with subsequent analysis using gas chromatography with electron capture detection. The suite of compounds included are those that have been of environmental significance for years (such as 2,4,6-trinitrotoluene, hexahydro-1,3,5-trinitro-1,3,5-triazine, and dinitrotoluenes) and are the subject of several U.S. Environmental Protection Agency SW-846 methods. The procedures presented in this study are the product of years of development and refinement of methods used for the analysis of many real-world samples by the USACHPPM explosives analysis laboratory. The development, performance, advantages, and details of these procedures are described. The extension of these methods to the analysis of other media is also briefly discussed.     

An evaluation of analytical quality for selected PAH measurements in a fuel-contaminated soil

The measurements of polycyclic aromatic hydrocarbons (PAHs) in soil require optimized analytical methods that assess reliable mass fraction results. This is particularly important for analysing very complex matrix such as contaminated soils with crude fuels. The main objectives of this work were focused to minimize analytical effort and assess result reliability in analysis of PAH by high-performance liquid chromatography with fluorescence detection (HPLC/FD). First, analysis of soil samples with/without fuel contamination was well established by sonication (US) and pressurized fluid extraction (ASE) using minimal amount of sample and minimal treatment of sample. On the other hand, an extensive study with spiked and field soil samples was performed by checking proportional and constant bias for analytical validation. The major components for estimating uncertainty contributions were evaluated on the basis of intermediate precision with two fuel matrix, PAH mass fraction and dates of analyses.     

Determination of the herbicide 4-chloro-2-methylphenoxyacetic acid and its main metabolite, 4-chloro-2-methylphenol in water and soil by liquid chromatography-electrospray tandem mass spectrometry

A rapid and sensitive LC-electrospray tandem mass spectrometry method has been developed for the quantitation of 4-chloro-2-methylphenoxyacetic acid (MCPA) and 4-chloro-2-methylphenol in both water and soil samples. Soil samples were extracted in alkaline media and cleaned-up by solid-phase extraction with C18 cartridges before LC-MS analysis. The selectivity and sensitivity offered by the triple quadrupole allowed the direct injection of the water samples rendering a sample throughput of around 100 samples per day, without any sample pretreatment, rendering for MCPA a limit of detection of 40 ng/l. In order to increase the method sensitivity, mainly for metabolite, a previous solid-phase extraction step was also performed. The method was validated by means of recovery experiments using fortified water and soil samples, obtaining satisfactory recoveries for both compounds in water and for MCPA in soil. The validated procedures can be used for the specific monitoring of residues of MCPA and its main metabolite in environmental samples, as ground and surface waters and soils, providing more selectivity and sensitivity than the current UV-based methodology. Besides, sample manipulation is greatly reduced in comparison to other GC-MS based methods which require a previous derivatization.     

Method for combined biometric and chemical analysis of human fingerprints

This paper describes a method for combining direct chemical analysis of latent fingerprints with subsequent biometric analysis within a single sample. The method described here uses ion mobility spectrometry (IMS) as a chemical detection method for explosives and narcotics trace contamination. A collection swab coated with a high-temperature adhesive has been developed to lift latent fingerprints from various surfaces. The swab is then directly inserted into an IMS instrument for a quick chemical analysis. After the IMS analysis, the lifted print remains intact for subsequent biometric scanning and analysis using matching algorithms. Several samples of explosive-laden fingerprints were successfully lifted and the explosives detected with IMS. Following explosive detection, the lifted fingerprints remained of sufficient quality for positive match scores using a prepared gallery consisting of 60 fingerprints. Based on our results (n?=?1200), there was no significant decrease in the quality of the lifted print post IMS analysis. In fact, for a small subset of lifted prints, the quality was improved after IMS analysis. The described method can be readily applied to domestic criminal investigations, transportation security, terrorist and bombing threats, and military in-theatre settings.     

常见炸药的稳定同位素比值分析方法研究进展

炸药的深度比对与溯源对于爆炸案事件的侦破具有重大意义,以不同地域来源的原料或不同生产工艺生产的炸药,其组成元素的稳定同位素比值具有差异,因而稳定同位素比值可作为炸药深度比对与溯源的重要指标。稳定同位素比值质谱法(IRMS)作为一种高精度的稳定同位素比值测量手段,已逐渐发展成熟,与元素分析仪、气相色谱仪、液相色谱仪等仪器联用,在食品安全、环境保护、法庭科学等领域应用广泛。IRMS在炸药比对与溯源上亦发挥了重要作用,自1975年IRMS被应用于区分不同国家生产的三硝基甲苯(TNT)以来,IRMS已成功用于多种炸药的分析。但目前尚未见有文献系统地总结常见炸药的稳定同位素比值分析研究进展。该文介绍了稳定同位素比值分析的相关原理、仪器组成及特点,分别总结了硝酸铵、黑火药、TNT、太恩、黑索金等常见炸药的稳定同位素比值分析方法,汇总了文献报道的不同国家生产的硝酸铵、黑火药、TNT等炸药的稳定同位素比值。文章就不同炸药的稳定同位素比值差异、炸药生产、存储过程中相关因素对同位素比值的影响,爆炸前后稳定同位素比值的变化情况等内容进行了分析。本文还指出了目前炸药的稳定同位素比值分析研究中存在的问题,对可能的解决办法进行了讨论,对未来的发展方向提出了建议。     

新型样品前处理材料在环境污染物分析检测中的研究进展

针对复杂样品的分析和痕量目标物的检测,样品前处理是必不可少的,高效的样品前处理技术不仅可以去除或减小样品基质干扰而且能够实现分析物的富集,提高分析检测的准确性和灵敏度。近年来,固相萃取、磁分散固相萃取、枪头固相萃取、搅拌棒萃取、固相微萃取等高效的样品前处理技术已在环境污染物分析检测中获得广泛关注,萃取效率主要取决于萃取材料,所以新型的高效萃取材料一直是样品前处理研究领域的重要发展方向。该文总结和讨论了近年来新型样品前处理材料在环境污染物分析检测中的研究进展,主要聚焦在石墨烯、氧化石墨烯、碳纳米管、无机气凝胶、有机气凝胶、三嗪基功能材料、三嗪基聚合物、分子印迹聚合物、共价有机框架材料、金属有机框架材料以及它们的功能化萃取材料等。这些材料已经被应用于环境样品中不同类别污染物的萃取富集,如重金属离子、多环芳烃、塑化剂、烷烃、苯酚、氯酚、氯苯、多溴联苯醚、全氟磺酸、全氟羧酸、雌激素、药物残留、农药残留等。这些样品前处理材料具有高的表面积、大量的吸附位点,并涉及多种萃取机理如π-π、静电、疏水、亲水、氢键、卤键等相互作用。基于这些萃取材料的多种样品前处理技术与各类检测方法如色谱、质谱、原子吸收光谱、荧光光谱、离子迁移谱等相结合,已广泛应用于环境污染物的高灵敏分析检测。最后,该文总结了样品前处理发展中存在的问题,并展望了其未来在环境分析中的发展趋势。     

Studies of human and veterinary drugs' fate in environmental solid samples--analytical problems

The improvement of medical care worldwide is one of the reasons for the increasing production of pharmaceutical products. Human medicines are affordable to a greater proportion of the world's population. But a significant amount of used pharmaceuticals can create problems--accessibility to high volume production pharmaceuticals contributes to an increased contamination in the environment and the possibility of adverse effects on humans and animals. Many of these substances and their metabolites end up in the soil, sediments, and sludge. Knowledge regarding the environmental occurrence of pharmaceutical products is increasing, but information in the peer-reviewed literature regarding the fate and effects of most pharmaceuticals is limited. One of the reasons for this lack of data is that, until now, there have been few analytical methods capable of detecting these compounds at the low levels, which might be expected in the environment. This review article covers recent developments in the analysis of pharmaceuticals in environmental solid matrices (including soil, sediments, and sludge). We will report applications of different solid sample extraction methods, and current advances in liquid chromatography coupled with mass spectrometry for detection and identification of selected drugs in sludge, soils, manure, and sediments.     

A comparative study of solvent extraction of total petroleum hydrocarbons in soil

Three non-specific methods for the extraction of total petroleum hydrocarbons (TPH) from soil into organic solvent were compared. The techniques used for sample preparation were Soxhlet extraction, closed-vessel microwave-assisted extraction, and CEN shake extraction. The total concentrations of extracted compounds in the boiling point range of C10–C40 were determined by gas chromatography with flame ionization detection. The best recovery (99%) and repeatability (±3%) from standard oil mixtures were obtained with microwave-assisted extraction. However, the different extraction methods exhibited different behaviour when spiked soil samples were extracted. The best repeatability was obtained with CEN shake extraction (±6%) but the repeatability values for Soxhlet and microwave-assisted methods were quite high (>20%). However, the larger uncertainties of the latter extraction methods does not necessarily limit the applicability of these methods to the determination of petroleum hydrocarbons in soil, as in the assessment of soil contamination the expanded uncertainty of the result is usually not limited by analytical uncertainty, but rather by the uncertainty of the primary sampling stage. However, distinctive variation found in the chromatographic profiles illustrates that discretion should be obeyed when chromatograms obtained after application of different extraction methods on petroleum contaminated samples are to be used in the fingerprinting or age dating studies. Otherwise, misleading conclusions concerning the age of spillage could be drawn.     

大气颗粒物中有机物色谱分析的样品制备技术

大气颗粒物中有机物成分分析对深入研究大气颗粒物对人类健康、环境、气候、生态的影响,解析气溶胶来源,制定颗粒物控制相关法规,以及风险管理方法具有重要意义。由于颗粒物中的有机组分种类繁多,分析复杂,目前仅10%~20%的有机物得到了定性和定量分析。因此,大气细颗粒中有机物的分析已成为环境分析领域的优先发展方向。色谱是大气颗粒物中有机物分析的主要方法,而样品制备则是影响分析速度和精度的关键步骤。本文对颗粒物中有机组分色谱分析前的样品制备方法进行了综述,介绍了索氏提取、超声辅助提取、微波辅助提取、加压溶剂提取等溶剂提取方法以及热解吸提取方法,并重点介绍了这些方法在大气颗粒物样品处理中的应用,总结了各种方法的优缺点。     

Enhanced extraction of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in the presence of sodium dodecyl sulphate and its application to environmental samples

A method for enhanced extraction of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) from environmental samples is developed with the assistance of sodium dodecyl sulphate (SDS) surfactant. In this study, the concentration of SDS surfactant and other analytical parameters are optimized on a high-performance liquid chromatography-UV system. An isocratic flow of 1.0 mL/min with mobile phase acetonitrile-water; 70:30 (v/v) at 230 nm wavelength on a reverse-phase amide column is used for baseline separation of explosives and making calibration curves. The amount of recovered explosives from spiked soil and water samples are calculated. The limits of detection obtained for HMX and RDX standards are 1.5 and 3.8 ppb (S/N=3), respectively, which are much better than obtained by the Environmental Protection Agency method 8330. The recoveries are found to be enhanced by 1.7 and 1.6-fold with SDS solution as compared to water for HMX and RDX, respectively, from soil samples.