建立火场样品中汽油残留物ATD-GC-MS检验结果的评价方法

目的建立火场中汽油燃烧残留物ATD-GC-MS检验结果评价方法。方法将模拟燃烧样品用ATD-GC-MS法检验,检验结果通过对芳烃、烷烃、茚满、和萘系列的4个特征离子色谱图与已知汽油作比较,并利用向量夹角法计算样品与汽油色谱指纹图的相似度来对检验结果作评价。结果有汽油作助燃剂的模拟燃烧样品与汽油色谱指纹图的相似度一般大于90%,无汽油作助燃剂的样品则在60%以下。结论利用样品的4个特征离子色谱图与已知汽油作比较,并结合样品与汽油色谱指纹图相似度的计算,能对检验结果作出客观、可靠和准确的评价。     

ATD—GC—MS法测定火场样品中痕量汽油燃烧残留物

目的为火场样品中痕量汽油残留物的检测建立一种简便、高灵敏度的检验方法和可靠的检验结果评判方法。方法用TenaxTA吸附管吸附富集火场样品中的汽油成分,然后用ATD—GC—MS法自动解吸和检测。通过模拟燃烧实验,探讨了检验结果的评判方法：根据样品的m／z（57＋85）、m/z（91＋105＋119）、m／z（117＋131）和m/z（128＋142＋156）四个质量色谱图与已知汽油作比较来对检验结果作评判。结果6组模拟燃烧实验中凡有汽油作助燃剂的样品．均检出汽油残留物成分。结论所建立的方法具有操作简便,检测灵敏度高,杂质干扰少,定性结论准确可靠等特点。可用于实际火场样品中痕量汽油残留物的检测。     

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。     

固相微萃取与气相色谱仪联用技术在火场助燃剂检验中的应用

目的建立检验纵火案件现场燃烧残留物中助燃剂的一种方法。方法利用固相微萃取器吸附浓缩燃烧残留物中的挥发性气体,使用气相色谱仪对挥发性气体进行定性分析。结果固相微萃取与气相色谱仪联用能较好地对火场不同介质燃烧残留物中汽油、煤油、柴油等助燃剂进行种类认定。结论该方法简便易行。     

调和汽油的GC-MS检验与区分

调和汽油在涉火案件中出现的频率逐渐增加,其特殊的组成可能对成分研判造成干扰。为准确识别汽油组分,区分不同来源的调和汽油,本文依托气相色谱–质谱（GC-MS）检验了部分典型调和油品,分析了相关样品的谱图特征并进行归类。结果表明,案件中常见的调和油品按照谱图主要特点可划分为添加剂异常、异构烷烃异常、直链烷烃异常和多组分异常四类。其中前两类对汽油及其残留物鉴定基本不构成干扰,而直链烷烃异常类油品可能引起误判,多组分异常类油品则不宜轻易下汽油结论。该研究结果对特殊调和汽油及其残留物的检验鉴定有一定的指导意义,对于涉火案件中汽油的比对分析和来源推断具有实战应用价值。     

Tenax GR吸附解析技术在火场汽油残留物提取检验中的应用研究

目的针对火灾现场常规提取检验方法操作复杂、容易导致汽油残留物有效成分丢失等问题,研究建立采用Tenax GR吸附解析技术简便、高效提取检验汽油残留物的方法。方法将Tenax GR吸附管放入相关检材中,密封后在60℃烘箱中加热1h,经热脱附仪解析后使用气质联用仪分析。结果Tenax GR吸附解析技术可以检验汽油残留物中特征组分,主要包括甲苯、二甲基苯、三甲基苯、四甲基苯、萘、甲基萘及茚满类化合物。该技术的检测限为0.25pL/mL,同时放入6根吸附管做稳定性实验,其相对标准偏差(RSD)为2.43%。该技术进行7、15、30、60、90d等不同阶段的保存实验,其相对偏差分别为6.3%、14.4%、8.7%、18.3%、11.6%。结论该技术操作方便、灵敏度高、稳定性好,适用于火灾现场中汽油残留物的提取检验。     

吸附管／气相色谱／质谱法分析纵火案的纵火剂残留物

用吸附管(AT)/气相色谱(GC)/质谱(MS)法检测纵火残留物中轻质矿物油是通过吸附管动态吸附检材中可挥发的有机物,然后通过热脱附将挥发物送至GC及GC/MS中检测。它既适用于轻组份的碳氢化合物,如汽油,也适用于较高分子的碳氢化合物,如柴油和煤油。用沸石预处理样品克服了样品中水分对鉴定的干扰。用本方法能够得到比过去所使用的溶剂提取法或顶空法(HS)更高的吸附效率和灵敏度,解决了以往由于残留物中热解产物干扰所造成的GC图形混乱复杂,难以准确分析鉴定的问题。用本方法分析纵火或火灾案件中常见的残留物-轻质矿物油,具有快速、灵敏、准确和简便等特点,可广泛应用于公安、司法和保险等各个领域。     

应用SPME—GC／MS／PFPD技术测定烃类及硫化物标记物鉴别汽油、煤油、柴油燃烧残留物

目的利用汽油、煤油、柴油等助燃剂中特殊的硫化合物类标记物,建立一种新型的火场助燃剂残留物分析方法。方法应用固相微萃取气质联用一脉冲火焰光度检测器（SPMBGC／MS／PFPD）技术同步测定烃类、芳香烃类及硫化合物类。结果确定了13种特征硫化合物。质谱烃类数据和PFPD硫化合物数据稳定,RSD％值分别≤0．75和≤1．29。结论该方法能对各种纵火现场助燃剂微量燃烧残留物进行有效鉴别。     

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。     

乳化炸药爆炸残留物分析

目的 探讨乳化炸药爆炸案件中导致爆炸残留物中铵根离子、硝酸根离子含量偏低的原因。方法 通过实际爆炸案例分析,实地了解乳化炸药制造工艺,采用离子色谱法检验爆炸案件及爆炸实验提取的残留物中铵根离子和硝酸根离子成分含量。通过与空白样本对比,分析导致乳化炸药爆炸残留物中铵根离子、硝酸根离子含量降低的原因。结果 经过生产工艺改进的乳化炸药爆炸后,其残留物中检出硝酸根和铵根离子的含量没有明显高于现场空白样本。结论 通过考察分析、对比检验,发现生产工艺改进是导致乳化炸药爆炸残留物中铵根离子和硝酸根离子含量偏低的原因。针对这一问题,本文提出了一些相应的解决方案。     

Progress Toward the Determination of Correct Classification Rates in Fire Debris Analysis II: Utilizing Soft Independent Modeling of Class Analogy (SIMCA)

A multistep classification scheme was used to detect and classify ignitable liquid residues in fire debris into the classes defined by the ASTM E1618‐10 standard method. The total ion spectra (TIS) of the samples were classified by soft independent modeling of class analogy (SIMCA) with cross‐validation and tested on fire debris. For detection of ignitable liquid residue, the true‐positive rate was 94.2% for cross‐validation and 79.1% for fire debris, with false‐positive rates of 5.1% and 8.9%, respectively. Evaluation of SIMCA classifications for fire debris relative to a reviewer's examination led to an increase in the true‐positive rate to 95.1%; however, the false‐positive rate also increased to 15.0%. The correct classification rates for assigning ignitable liquid residues into ASTM E1618‐10 classes were generally in the range of 80–90%, with the exception of gasoline samples, which were incorrectly classified as aromatic solvents following evaporative weathering in fire debris.     

The evaluation of the extent of transporting or "tracking" an identifiable ignitable liquid (gasoline) throughout fire scenes during the investigative process

Tests have determined that boots or shoes of individuals at a fire scene do not transport sufficient contaminants ("tracking") through the fire scene to produce a positive laboratory result for the presence of gasoline in a fire scene that was not present at the time of the fire. Questions about the validity of forensic laboratory results have been raised on the basis that low-level gasoline residues detected in the laboratory samples could have been the result of transporting the residue by footwear contaminated from the fire scene ("tracking"). The data collected in this study establish that "tracking" does not lead to false-positive laboratory results. Canines trained and experienced in the detection of trace ignitable liquid residues were also utilized in this study. The canine results confirmed that properly trained canines show a higher sensitivity than do standard ASTM laboratory techniques for fire debris analysis. In a few cases, canines responded to contamination, but laboratory testing (which is the definitive indicator) did not produce positive results.     

Using Alkylate Components for Classifying Gasoline in Fire Debris Samples

The characteristic that discriminates gasoline from other ignitable liquids is that it contains high‐octane blending components. This study elaborates on the idea that the presence of gasoline in fire debris samples should be based on the detection of known high‐octane blending components. The potential of the high‐octane blending component alkylate as a characteristic feature for gasoline detection and identification in fire debris samples is explored. We have devised characteristic features for the detection of alkylate and verified the presence of alkylate in a large collection of gasoline samples from petrol stations in the Netherlands. Alkylate was detected in the vast majority of the samples. It is demonstrated that alkylate can be detected in fire debris samples that contain traces of gasoline by means of routine GC‐MS methods. Detection of alkylate, alongside other gasoline blend components, results in a more solid foundation for gasoline detection and identification in fire debris samples.     

纵火现场中汽油、煤油和柴油残留物的ATD／GC／MS法检测

目的为火场中汽油、煤油和柴油残留物的检测建立一种简便、高灵敏度的ATD／GC／MS检验方法。方法采用Tenax TA吸附管吸附富集检材中的汽油、煤油和柴油成分。然后用美国PE公司的ATD／GC／MS仪器进行全自动的解吸和分析检测。结果检材中汽油、煤油和柴油的检测极限分别达0．05、0.2、0．2pL／mL。结论该方法具解吸和分析检测过程自动化。操作简便快捷，检测灵敏度高。杂质干扰少等特点，可用于实际火场皆汽油、煤油和柴油残留物的检测。     

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.     

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.     

Comparison of gasolines using gas chromatography-mass spectrometry and target ion response

Gas chromatography-mass spectrometry was used to compare gasoline samples obtained from different sources based on the difference in amounts of certain components found in the headspace of gasoline using target response data. Many suspected arson cases involve comparing an ignitable liquid extracted from fire debris to a liquid found in a suspect's possession to determine if they could have had a common source. Various component ratios are proposed for determining if an unevaporated gasoline sample could have originated from the same source as an evaporated gasoline extracted from fire debris. Fifty and 75% evaporated gasoline samples were both found to contain similar ratios of certain components when compared with its unevaporated source gasoline. The results of the comparisons in this study demonstrate that for cases involving gasoline that has been evaporated up to 50% and extracted from pine, it is possible to eliminate comparison samples as originating from the same source. The results of the 75% comparisons suggest it may be possible to apply the same type of comparison to cases involving 75% evaporated gasoline.