A solid-phase microextraction method for the detection of ignitable liquids in fire debris

A solid-phase microextraction (SPME) procedure involving direct contact between the SPME fibers and the solid matrix and subsequent gas chromatography/mass spectrometric analysis for the detection of accelerants in fire debris is described. The extraction performances of six fibers (100 mum polydimethylsiloxane, 65 mum polydimethylsiloxane-divinylbenzene, 85 mum polyacrylate, 85 mum carboxen-polydimethylsiloxane, 70 mum Carbowax-divinylbenzene, and 50/30 mum divinylbenzene-Carboxen-polydimethylsiloxane) were investigated by directly immersing the fibers into gasoline, kerosene, and diesel fuel. For simulated fire debris, in the direct contact extraction method, the SPME fiber was kept in contact with the fire debris matrix during extraction by penetrating plastic bags wrapping the sample. This method gave comparable results to the headspace SPME method in the extraction of gasoline and kerosene, and gave an improved recovery of low-volatile components in the extraction of diesel fuel from fire debris. The results demonstrate that this procedure is suitable as a simple and rapid screening method for detecting ignitable liquids in fire debris packed in plastic bags.     

Chemical signature of ecstasy volatiles by comprehensive two-dimensional gas chromatography

A method for ecstasy volatiles 'signature' analysis based on two-dimensional gas chromatography separation and time-of-flight mass spectrometry detection (GC×GC-TOFMS) is presented. Organic impurity volatiles were extracted by head space solid phase microextraction (HS-SPME). The final column phase choice of the four different column combinations tested was a low-polarity 5% phenyl polysilphenylene-siloxane coupled with a polyethylene glycol phase, which best displayed the complex impurity profile. Second dimension ((2)D) retention time reproducibility was found to be about 1% RSD, and area reproducibility of SPME sampling was just over 5% RSD for compounds with S/N ratio of about 100. High similarity of TOFMS spectra of impurities was obtained against commercial MS libraries. 16 components from the two-dimensional profiles were selected for comparison of the 24 ecstasy tablets, most of which proved to be benzodioxole derived compounds. All tablets were correctly classified in eight groups according to their post-tabletting characteristics, when appropriate data pre-treatment was applied. Principal component analysis revealed clustering of samples according to the country of origin. Samples from Macedonia were elevated in N-formyl-MDMA and N-acetyl-MDMA while samples from Australia were elevated in 3,4-methylenedioxypropane and 3,4-methylenedioxyacetophenone. Furthermore, three components were found to be unique for one of the source countries. The additional separation of components on the (2)D column, increased response due to modulation, high acquisition rate with full mass spectra using TOFMS detection, and MS deconvolution extend the possibility of detecting additional markers and route-specific components, especially of low abundant, polar components.     

GC-MS of ignitable liquids using solvent-desorbed SPME for automated analysis

Solid-phase microextraction (SPME) is well documented with respect to its convenience and applicability to sampling volatiles. Nonetheless, fire debris analysts have yet to widely adopt SPME as a viable extraction technique, although several fire debris studies have demonstrated the utility of SPME coupled with gas chromatography-mass spectrometry (GC-MS) to identify ignitable liquids. This work considers the expansion of SPME sampling from the customary thermal desorption mode to solvent-based analyte desorption for the analysis of ignitable residues. SPME extraction fibers are desorbed in 30 microL of nonaqueous solvent to yield a solution amenable to conventional GC-MS analysis with standard autosampler apparatus. This approach retains the advantages of convenience and sampling time associated with thermal desorption while simultaneously improving the flexibility and throughput of the method. Based on sampling results for three ignitable liquids (gasoline, kerosene, anddiesel fuel) in direct comparisons with the widely used activated charcoal strip (ACS) method this methodology appears to be a viable alternative to the routinely used ACS method.     

Semi-automatic analysis of fire debris

Automated analysis of fire residues involves a strategy which deals with the wide variety of received criminalistic samples. Because of unknown concentration of accelerant in a sample and the wide range of flammable products, full attention from the analyst is required. Primary detection with a photoionisator resolves the first problem, determining the right method to use: the less responsive classical head-space determination or absorption on active charcoal tube, a better fitted method more adapted to low concentrations can thus be chosen. The latter method is suitable for automatic thermal desorption (ATD400), to avoid any risk of cross contamination. A PONA column (50 mx0.2 mm i.d.) allows the separation of volatile hydrocarbons from C(1) to C(15) and the update of a database. A specific second column is used for heavy hydrocarbons. Heavy products (C(13) to C(40)) were extracted from residues using a very small amount of pentane, concentrated to 1 ml at 50 degrees C and then placed on an automatic carousel. Comparison of flammables with referenced chromatograms provided expected identification, possibly using mass spectrometry. This analytical strategy belongs to the IRCGN quality program, resulting in analysis of 1500 samples per year by two technicians.     

Forensic applications of pyrolysis capillary gas chromatography

A simple system of pyrolysis capillary gas chromatography has been used to improve discrimination and long-term reproducibility in the analysis of polymers particularly alkyd based paints typically encountered in forensic casework. This involved the coupling of a Pye Curie-point pyrolyser to the inlet port of a capillary gas chromatograph operated in the splitless mode. Examples of pyrograms demonstrating improved differentiation of alkyd paints, and also examples of other architectural and automotive paints, automobile rubbers, adhesives, polyurethane foams and fibres are shown.     

Forensic toxicologic analysis of methamphetamine and amphetamine in body materials by gas chromatography/mass spectrometry

Qualitative and quantitative analysis of methamphetamine and amphetamine in biologic materials was carried out by gas chromatography/mass spectrometry. A deuterium-labeled methamphetamine was employed as an internal standard with a detection limit of 50 pg and absolute stability and reproducibility. Blood was found to be the best material for estimation of the toxicity of the stimulant drug. It can be replaced by muscle which contains methamphetamine concentrations close to those of blood. The authors' classification of the toxic blood levels of methamphetamine from therapeutic to fatal doses was confirmed by additional data obtained from new case studies.     

二维气相色谱检测爆炸残留物中TNT

目的建立二维气相色谱结合ECD检测爆炸残留物中TNT的方法。方法利用Dean-Switch系统进行二维无死体积切换，通过切换时间的准确选择，使粉尘样品提取液无需净化进样，即可达到分离彻底、高灵敏度。结果在案件检测应用中，效果良好。     

The sampling of ignitable liquids on suspects’ hands

In arson cases, the collection and detection of traces of ignitable liquids on a suspect's hands can provide information to a forensic investigation. Police forces currently lack a simple, robust, efficient and reliable solution to perform this type of swabbing.In this article, we describe a study undertaken to develop a procedure for the collection of ignitable liquid residues on the hands of arson suspects. Sixteen different collection supports were considered and their applicability for the collection of gasoline traces present on hands and their subsequent analysis in a laboratory was evaluated. Background contamination, consisting of volatiles emanating from the collection supports, and collection efficiencies of the different sampling materials were assessed by passive headspace extraction with an activated charcoal strip (DFLEX device) followed by gas chromatography–mass spectrometry (GC–MS) analysis. After statistical treatment of the results, non-powdered latex gloves were retained as the most suitable method of sampling.On the basis of the obtained results, a prototype sampling kit was designed and tested. This kit is made of a three compartment multilayer bag enclosed in a sealed metal can and containing three pairs of non-powdered latex gloves: one to be worn by the sampler, one consisting of a blank sample and the last one to be worn by the person suspected to have been in contact with ignitable liquids. The design of the kit was developed to be efficient in preventing external and cross-contaminations.     

Sampling and recovery of ignitable liquid residues (ILRs) from fire debris using capillary microextraction of volatiles (CMV) for on-site analysis

A new, fast, and ultra-sensitive headspace sampling method using the Capillary Microextraction of Volatiles (CMV) device is demonstrated for the analysis of ignitable liquid residues (ILRs) in fire debris. This headspace sampling method involves the use of a heated can (60°C) to aid in the recovery of volatile organic compounds (VOCs) from medium and heavy petroleum distillates. Our group has previously reported the utility of CMV to extract gasoline at ambient temperature in less than 5 min in the field. This work evaluates the recovery and analysis of low mass loadings (tens of ng) of VOCs from charcoal lighter fluid, kerosene, and diesel fuel. Nonane, decane, undecane, tridecane, tetradecane, and pentadecane were selected for evaluation of recovery to represent these ILR classes. The face-down heated can headspace sampling technique was compared to the previously reported, non-heated, paper cup headspace sampling technique. Mass recovery improvements of 50%–200% for five of the six target compounds in diesel fuel were achieved compared to the non-heated sampling method. The average relative standard deviation (reported as % RSD) between the replicate trials decreased from an average of 28% to 6% when using the heated can method. Ignitable liquids were spiked onto burned debris in a live burn exercise and sampled using the heated can and paper cup headspace sampling techniques. The heated sampling technique reported here, for the first time, demonstrates an effective extraction method that when coupled to a portable GC–MS instrument allows for a sampling and analysis protocol in the field in less than 30 min.     

Absorption of ignitable liquids into polyethylene/polyvinylidine dichloride bags

Clear plastic bags are often used for the collection, sampling and storage of ignitable liquid evidence. They are popular because they are easy to store. transport and are inexpensive. Cryovac and Globus brand polyethylene/polyvinylidine dichloride bags were tested for suitability in storing ignitable liquid evidence. Standards of diesel, kerosene and gasoline were placed in the bags and sampled by passive headspace adsorption. The bags were then heated to determine if absorbed components of the standards could be released upon heating. Recovered extracts were analyzed by GC and GCMS. These bags were found to absorb components of diesel, kerosene, and gasoline. and were also found to produce interfering by-products that obstruct the chromatographic results. Evidence containers need to be tested to ensure that low levels of ignitable liquids are not missed.     

Acid alteration of several ignitable liquids of potential use in arsons

Ignitable liquids such as fuels, alcohols and thinners can be used in criminal activities, for instance arsons. Forensic experts require to know their chemical compositions, as well as to understand how different modification effects could impact them, in order to detect, classify and identify them properly in fire debris. The acid alteration/acidification of ignitable liquids is a modification effect that sharply alters the chemical composition, for example, of gasoline and diesel fuel, interfering in the forensic analysis and result interpretation. However, to date there is little information about the consequences of this effect over other accelerants of interests. In this research paper, the alteration by sulfuric acid of several commercial thinners and other accelerants of potential use in arsons is studied in-depth. For that purpose, spectral (by ATR-FTIR) and chromatographic (by GC–MS) data were obtained from neat and acidified samples. Then, the spectral and chromatographic modifications of each studied ignitable liquid were discussed, proposing several chemical mechanisms that explain the new by-products produced and the gradual disappearance of the initial compounds. Hydrolysis, Fischer esterification and alkylation reactions are involved in the modification of esters, alcohols, ketones and aromatic compounds of the studied ignitable liquids. This information could be crucial for correctly identifying these accelerants. Additionally, an exploratory analysis revealed that some of the most altered ignitable liquid samples might be very similar with each other, which could have impact on casework.     

自动热脱附气相色谱-质谱法分析火场助燃剂汽油成分

目的建立检验纵火案件现场燃烧残留物中助燃剂汽油成分的方法。方法利用自动热脱附技术对火场残留物中的助燃剂进行富集、浓缩、脱附后经气-质联用仪（GG-MS）分析。结果结合现场燃烧环境运用目标化合物法能够判定是否含有助燃剂汽油成分。结论该方法简便易行。     

Use of a solid absorbent and an accelerant detection canine for the detection of ignitable liquids burned in a structure fire

ABSTRACT: Ignitable Liquid Absorbent^™ (ILA), a commercial solid absorbent intended to assist fire scene investigators in sample location and collection, has been field tested in three separate room fires. The ability of the ILA to detect and absorb different amounts of gasoline, odorless paint thinner, and camp fuel on two different substrates after a full-scale burn was assessed against results from an accelerant detection canine and laboratory analysis using gas chromatography-mass spectrometry (GC-MS). The canine correctly alerted on most of the panels that contained an ignitable liquid after the fire, while the ILA indicator dye failed to indicate in the presence of gasoline and camp fuel. GC-MS results for ignitable liquid residue from each panel and from the ILA showed that ILA absorbed odorless paint thinner and camp fuel from most of the test panels, but failed to absorb gasoline from the panels on which gasoline was confirmed to be present.     

Alternative fuels in fire debris analysis: biodiesel basics

Alternative fuels are becoming more prominent on the market today and, soon, fire debris analysts will start seeing them in liquid samples or in fire debris samples. Biodiesel fuel is one of the most common alternative fuels and is now readily available in many parts of the United States and around the world. This article introduces biodiesel to fire debris analysts. Biodiesel fuel is manufactured from vegetable oils and/or animal oils/fats. It is composed of fatty acid methyl esters (FAMEs) and is sold pure or as a blend with diesel fuel. When present in fire debris samples, it is recommended to extract the debris using passive headspace concentration on activated charcoal, possibly followed by a solvent extraction. The gas chromatographic analysis of the extract is first carried out with the same program as for regular ignitable liquid residues, and second with a program adapted to the analysis of FAMEs.     

ASTM standards for fire debris analysis: a review

The American Society for Testing and Materials (ASTM) recently updated its standards E 1387 and E 1618 for the analysis of fire debris. The changes in the classification of ignitable liquids are presented in this review. Furthermore, a new standard on extraction of fire debris with solid phase microextraction (SPME) was released. Advantages and drawbacks of this technique are presented and discussed. Also, the standard on cleanup by acid stripping has not been reapproved.Fire debris analysts that use the standards should be aware of these changes.     

火场中尸体的法医学分析

火场中的尸体是法医病理工作者较常见的案件,在这种案件中,判断是生前烧死还是死后焚尸具有非常重要的意义。本文就相关文献关于火灾死亡案件的尸体内部、外部征象、现场特点、以及以COHb为主的实验室结果加以综述,目的在于阐明这些特征在实际案件中的作用和应用,为法医工作者解决此类案件提供参考。     

全二维气相色谱在刑事技术中的应用

综述了近年来发展起来的全二维气相色谱(GCхGC)技术正交分离系统原理及其特点以及在刑事技术中应用的发展前景。     

Forensic examination of wax seals by thin-layer chromatography

An attempt has been made to separate some of the constituents of wax seals by thin-layer chromatography, and thereby differentiate them. The method is suitable for routine forensic examinations.     

Forensic toxicologic analysis of methamphetamine and amphetamine optical isomers by high performance liquid chromatography

Optical isomers (d and l) and racemic compounds (dl) of methamphetamine (MAMP) and amphetamine (AMP), and biologic materials including those substances, could be analyzed by high performance liquid chromatography. Examining the temperature for the analysis, 40 degrees C was the optimal condition in the reproducibility of separated MAMP-isomers. The reproducibility at the temperature did not vary significantly. The measured values of optical isomers were 0.116 +/- 0.012, 1.082 +/- 0.070 and 8.984 +/- 0.136 for the mixing ratios (l/d) of 0.111, 1.000, and 9.000, respectively. The detection limit for both d- and l-isomers was 25 ng. The analytic result of hair specimens from two stimulant abusers by the present method indicates that they contained only d-MAMP and d-AMP, which is believed to have the strongest pharmacologic effect among the optical isomers of MAMP. The coefficient of variation in the analysis of five replicate standards, prepared by adding 1,000 ng each of racemate MAMP and AMP to hair, was less than 4%. The measured value against l/d = 1.000 was 1.040 +/- 0.040 in MAMP and 0.980 +/- 0.030 in AMP. The detection limit for both racemate MAMP and AMP accumulated in hair was 250 ng. The analysis of the optical isomers by our method would contribute to identifying the smuggling routes or the illicit method.     

Extraction, derivatization, and analysis of vegetable oils from fire debris

Vegetable oils have the ability to spontaneously heat under certain conditions, which may lead to spontaneous ignition. While the oils are not often encountered in forensic casework, they may be suspected in some fire cases. As these oils are not effectively analyzed using traditional fire debris analysis methods, a protocol must be established for extracting vegetable oils from fire debris. In this study, a protocol was developed for the extraction, derivatization, and analysis of vegetable oils from fire debris. Three derivatization methods were compared to establish an optimal derivatization procedure to convert the fatty acids found in vegetable oils to the fatty acid methyl esters (FAMEs) used in analysis. Three different gas chromatograph columns and programs were examined to determine which was best suited for the separation and analysis of FAMEs. The procedure was tested and refined using a variety of neat and burned vegetable oils, in addition to extractions from oils burned on commonly encountered fire debris materials. The findings of this research will serve as a starting point for further understanding and research of vegetable oils in fire debris.