Fisher判别在气相色谱-质谱分析助燃剂燃烧残留物中的应用

为寻找一种用于火场助燃剂燃烧残留物鉴定的更为准确、有效的模式识别方法,对7种常见助燃剂在不同载体上的燃烧残留物样品及未知送检样品进行气相色谱-质谱（GC-MS）分析测试,通过特征组分分析鉴定出未知样品中含有汽油成分。同时运用Fisher判别及PCA（主成分分析）/Fisher判别联用两种判别方法对样本数据进行了分析处理,PCA/Fisher判别联用的结果表明送检样本中含有硝基油漆稀料成分,而仅使用Fisher判别的结果表明送检样本中含有93^#汽油。通过将两种分析方法所得结果与GC-MS特征组分分析的结果进行比对发现,Fisher判别能够对7种助燃剂燃烧残留物的样本实现更有效的分类,对未知样本的判别更为有效。该研究结果为火场助燃剂鉴定提供了新的数据分析手段。     

汽油燃烧残留物标准样品制备及特征组分研究

汽油燃烧残留物的检测往往是纵火案件侦破的关键,对鉴定机构的检验(鉴定)能力有很高的要求。汽油燃烧残留物的鉴定需要已知样品进行比对分析,但目前还没有相应的标准样品可以提供。因此,建立汽油燃烧残留物标准样品有助于对鉴定机构相应的鉴定能力进行培养和考察。本研究以石英砂为燃烧载体,93号汽油为助燃剂,制备汽油燃烧残留物标准样品,对比研究了溶剂法和直接顶空进样法对汽油燃烧残留物的提取效果。气相色谱-质谱法的分析结果表明,汽油在燃烧前后的特征组分存在明显差异,不同的提取方法对检测结果有一定影响,但是特征组分的变化趋势是一致的,取代的芳烃和稠环芳烃等特征组分的鉴别和含量的相对大小可以作为汽油燃烧残留物鉴定的重要判定依据。     

熏蒸提取法对比测定不同土种中的微生物碳含量

土种是土壤发生分类中的最基础分类单元,基于土种的微生物量调查是土壤生物调查中的重要工作,其中微生物量以微生物碳含量表征。采用氯仿熏蒸提取法-碳光谱分析法和重铬酸钾氧化法对比测定土壤中的微生物碳含量,对于提取液中的有机碳含量,碳光谱分析法的检出限为0.11 mg/L,重铬酸钾氧化法的检出限为1.55 mg/L。在精密度试验中,对于熏蒸后的土样,碳光谱分析法的RSD为8.8%~9.9%,重铬酸钾氧化法的RSD为7.0%~17.6%。对于未熏蒸处理的土样,两种方法的RSD分别为5.3%~9.3%和9.3%~12.0%。微生物碳测试结果与土壤的水分含量相关性显著（p<0.05）。对比两种方法的测定结果,发现熏蒸土样的相对偏差范围为0.1%~49.4%,未熏蒸土样的相对偏差范围为0.0%~60.9%,低浓度样品的偏差较大。对于不同土种中微生物碳含量的测定,碳光谱分析法测得结果范围为146 μg/g dry soil~414 μg/g dry soil,重铬酸钾氧化法的范围为131 μg/g dry soil~407 μg/g dry soil,两种方法测定结果间无显著差异。结果表明,低浓度样品测定时采用重铬酸钾氧化法造成的误差较大,宜采用碳光谱分析法,两种方法均能有效测定不同土种中的微生物碳含量。     

裂解气相色谱-质谱分析火场残留物中助燃剂

通过对火灾现场助燃剂及其燃烧残留物进行分析，开展了基于裂解气相色谱-质谱法（PyGC-MS）的火场助燃剂分析方法。选取了汽油和柴油2种助燃剂以及棉布和聚对苯二甲酸乙二醇酯（PET）塑料2类载体，制备了助燃剂与载体的混合燃烧残留物。利用热分析技术确定样品的特征性温度，并对分析条件进行优化与选择。通过闪蒸分析和裂解分析的分步裂解方法，对样品进行了PyGC-MS分析。实验结果表明，PET载体原样燃烧残留物的裂解产物共有35个组分，而PET载体与汽油混合燃烧残留物和PET载体与柴油混合燃烧残留物的裂解产物只有25个组分，且各裂解产物的种类和含量均不相同。该法可对同一载体的自身燃烧残留物和与助燃剂混合燃烧残留物进行区分，适用于火灾残留物中助燃剂的分析，可对火场中是否存在助燃剂进行判别，为火灾性质的判断和火灾调查工作提供科学依据。     

稀土对红壤微生物量碳的影响

取过２０ 目筛黄筋泥（浙江龙游县, 桔园表层土,ｐＨＨ２０ 为５．１,有机质含量为２．３５％ , 每１００ ｇ 土的阳离子交换量为１０．５０ ｍｍｏｌ, 每１ ｋｇ 土的可溶态稀土总量为１１．４４ ｍｇ） 风干土若干, 以０,１０,５０,１００,２００,３５０ ｍｇ·ｋｇ－１的浓度水平分别加入混合稀土及单一稀土元素Ｐｒ,Ｓｍ ,Ｅｕ 等, 混合稀土的配比为Ｌａ∶Ｃｅ∶Ｐｒ∶Ｎｄ∶Ｓｍ∶Ｅｕ∶Ｇｄ∶Ｙ＝４∶４∶２∶２∶２∶１∶１∶４, 并对土样加蒸馏水至田间持水量的５０％ , 保持１００％ 的湿度在生化培养箱中于２５ ℃下恒温培养一周后进行微生物量的测定, 每个样重复３ 次, 土壤样品微生物量碳的测定方法采用氯仿熏蒸,０．５ ｍｏｌ·Ｌ－１ Ｋ２ＳＯ４ 提取法, 提取液中的有机碳浓度用自动定碳仪（ＴＯＣ）测定, 并由下式计算微生物量：ＳＭＢＣ＝ （ｃＥＣｔ－ ｃＥＣＯ）／０．４５, 式中,ＳＭＢＣ为土壤微生物量碳,ｃＥＣＯ,ｃＥＣｔ分别为氯仿熏蒸前后提取液中有机碳的浓度。测定结果表明, 不同稀土元素对土壤熏蒸前后的有机碳含量及其微生物量碳变化的影响规律基本相似, 随着稀土浓度的升高,熏蒸前后有机碳的含量都有不同程度的升高, 而且两者在量值上有逐渐     

快速生化需氧量微生物传感器的应用

采用混合菌BODseed制备微生物传感器快速监测生化需氧量（BOD）,研究了矫正溶液选择、样品自降解及恒温装置对测量准确度的影响。 结果表明,采用葡萄糖 谷氨酸矫正溶液测得污水处理厂污水结果较BOD5方法偏低50%以上,而以污水本身制作矫正曲线取得了与BOD5一致的测试结果;样品在保存6 h后有机物自降解会使测量结果偏低40%;快速BOD在线监测时不仅需要对微生物传感器恒温,同时也需要对样品及缓冲溶液恒温,这有利于样品快速接近缓冲溶液温度,减少空气饱和时间,从而提高监测效率,提升测试准确度。     

典型塑料载体与助燃剂燃烧残留物的闪蒸气相色谱-质谱分析

通过对火场常见塑料载体与助燃剂混合燃烧残留物的分析,发展一种适用此类燃烧残留物的火灾物证鉴定方法,对火场中是否存在助燃剂进行判断,避免漏检情况的发生。应用热分析技术确定合适的闪蒸温度,在此温度下对塑料载体与助燃剂混合燃烧残留物进行闪蒸分析,并从实验条件选择、可行性分析、定性分析三方面对闪蒸技术进行评价。结果表明,闪蒸气相色谱-质谱（Flash GC-MS）技术可以检测到热塑性聚合物塑料载体与助燃剂混合燃烧残留物中残留的助燃剂特征组分,可对火场中是否存在过助燃剂进行辨别。闪蒸气相色谱-质谱技术丰富了现代火灾物证鉴定技术,能进一步辅助火灾物证鉴定工作,使鉴定结论更准确、可靠。     

聚琥珀酸丁二酯的辐射交联及其生物降解性

对聚琥珀酸丁二酯（PBS1）采用两步法辐照，比其它辐照法得到的凝胶含量高，这是由于在室温下预先辐射所形成的交联网络结构减少了聚合物的降解。交联后的PBS1有较高的耐热变形性。通过酶降解试验和土需求量法降解实验，PBS1有很高的生物降解性，即使它产生了很高的交联结构。在65℃时，酶的降解率最高。由于交联样品所含有的交联网络结构阻碍它的降解，交联PBS1的生物降解失重低于未交联样品。     

取代基效应对三苯甲酸纤维素酯类吸附剂的吸附性能的影响

采用催化合成法制备三苯甲酸纤维素酯（CTB）、三（4-甲基苯甲酸）纤维素酯（CTMB）和三（4-氯苯甲酸）纤维素酯（CTCB），将其分别负载于Gas Chrom Q载体上，用不同类型的探针分子及气相色谱法表征其吸附性能，研究取代基团的电子效应和空间效应对其吸附性能的影响。实验结果表明：在三苯甲酸纤维素酯类吸附剂和苯衍生物吸附质的苯环上的取代基效应（电子效应和立体效应）对吸附质在吸附剂上的吸附热（-Δha）的影响显著，但两者的影响各不相同。     

蒙脱土修饰电极上某些神经递质的电化学行为

采用不同电化学方法对神经递质多巴胺（ＤＡ）在蒙脱土修饰电极上的行为进行了研究，结果发现，蒙脱土修饰膜地ＤＡ有明显的富集作用。在ＰＨ７．４时，ＤＡ强烈地富集在蒙脱土膜内，并显示完成的伏安响应而抗坏血酸（ＡＡ）和ＤＡＲ的代谢产物３，４－二羟基苯乙酸（ＤＯＰＡＣ）则无任何响应。采用计时库仑法测定了ＤＡ在蒙脱土膜内的表观扩散系数为２．３×１０＾－９ｃｍ＾２／ｓ，并计算了异相速率常数为２．７×１０＾－６ｃｍ     

火场助燃剂检验鉴定的干扰研究进展

火灾是影响公共安全最为常见的灾害之一,而放火更是严重威胁人民群众生命财产安全,属于典型的暴力犯罪.犯罪嫌疑人为了达到有效快速放火的目的,往往使用助燃剂实施放火,因而助燃剂的检验鉴定对于认定火灾性质起着至关重要的作用.然而火场情况复杂,容易对助燃剂物证检验鉴定产生较大干扰.在火灾发生发展的过程中,火场高温热环境会作用于已...     

高效液相色谱-气相色谱在线联用同时测定土壤中饱和烃和芳香烃

为加强对土壤中石油烃类污染物的风险管控,生态环境部已将石油烃类列为土壤中的重点监测项目.石油烃源于石油与合成油,是涵盖一定碳数范围的碳氢化合物,主要分为饱和烃和芳香烃两大类.芳香烃通常是高度烷基化的单环、双环与多环芳烃,其对人和动物的毒性较饱和烃大很多,因此,仅仅测定土壤中总石油烃含量难以准确评估其环境毒性.目前环境领...     

Cyclodextrin-enhanced in situ bioremediation of polyaromatic hydrocarbons-contaminated soils and plant uptake

In situ bioremediation of polycyclic aromatic hydrocarbons (PAH) polluted soils can be improved by the augmentation of degrading microbial populations and by the increase of hydrocarbon bioavailability. β-cyclodextrin (β-CD) significantly accelerate the induction of hydrocarbon biodegradation, but it is not still clear its effectiveness during final, slower stages of degradation. Moreover, it is yet not known if the PAH uptake from plants is influenced by the presence of CD. A field study was carried out by creating two plots (A and B). Diesel fuel was spread on the surface, and on plot B a commercial microbial consortium and β-CD were spread. Soybean was seeded in both plots. Soil samples were withdrawn every 10 cm layers from 0 to 60 cm depth, before fuel spreading, immediately after seeding and after soya harvesting. Chemical and microbial analyses were carried out throughout the process to characterize the soil and to determine residual PAHs. Soybean seeds were analyzed for PAH content. It was observed that β-CD induced a significant increase of PAH degradation rate. The microbial inoculum did not improve the degradation; biodegradation activity was strong in superficial layers, and some PAH leaching was observed, that was reduced by CD. The analysis of PAH in soyabeans revealed that an uptake of hydrocarbons occurred, and that it was more significant in plot B. This suggests that the β-CD-enhanced bioremediation process can further be improved by phytoremediation, that could also allow to simultaneously reach an additional profit from a non-food yield for biofuel production.     

Detailed analysis of petroleum hydrocarbon attenuation in biopiles by high-performance liquid chromatography followed by comprehensive two-dimensional gas chromatography

Enhanced bioremediation of petroleum hydrocarbons in two biopiles was quantified by high-performance liquid chromatography (HPLC) followed by comprehensive two-dimensional gas chromatography (GCXGC). The attenuation of 34 defined hydrocarbon classes was calculated by HPLC–GCXGC analysis of representative biopile samples at start-up and after 18 weeks of biopile operation. In general, a-cyclic alkanes were most efficiently removed from the biopiles, followed by monoaromatic hydrocarbons. Cycloalkanes and polycyclic aromatic hydrocarbons (PAHs) were more resistant to degradation. A-cyclic biomarkers farnesane, trimethyl-C13, norpristane, pristane and phytane dropped to only about 10% of their initial concentrations. On the other hand, C29–C31 hopane concentrations remained almost unaltered after 18 weeks of biopile operation, confirming their resistance to biodegradation. They are thus reliable indicators to estimate attenuation potential of petroleum hydrocarbons in biopile processed soils.     

喷气燃料裂解产物中芳烃的全二维气相色谱-质谱分析

采用全二维气相色谱-质谱联用仪(GC×GC-MS),通过优化程序升温和调制周期,建立了喷气燃料裂解产物中芳烃的定性定量分析方法。该方法对多环芳烃(PAH)同分异构体具有良好的分离能力。利用MS检测器谱库检索结果、芳烃标准品及相关的文献报道,对喷气燃料裂解产物中常见的单环芳烃、二环芳烃、三环芳烃及四环芳烃等共27种芳烃进行了准确定性,并利用外标GC×GC-FID法对其进行定量。定量结果表明,芳烃含量均随着裂解产气率的增加而增大,当裂解产气率达到22%时,二环芳烃开始产生,且其含量随着裂解产气率的增加呈指数形式增加。该方法与传统的气相色谱-质谱相比,具有更好的分离及定性能力,可应用于复杂样品的分离及其定性定量分析。     

Bioremediation of hydrocarbons contaminated waters and soils: monitoring by luminescent bacteria test

Bioremediation has proven successful in numerous applications to petroleum hydrocarbons or chlorinated aromatic hydrocarbons contaminated soils. There is increasing interest in application of biotoxicity tests for ecological assessment and for supporting management decisions for remediation. Luminescent assays, light-emitting bacteria in particular, can be a suitable tool for environmental analysis, and in vivo luminescence is a rapid and precise indicator of the toxic effects of xenobiotic on micro-organisms. In this study, three different strains of marine bioluminescent bacteria have been employed to follow the changes in biotoxicity occurring during the laboratory scale bioremediation of water and soil samples contaminated by hydrocarbons and collected at an industrial area. The degradation was made by hydrocarbons degrading bacteria, both of commercial sources and isolated from polluted water and soils. The samples were treated for 45 days. The toxicity of the samples, before and after the bioremediation, was determined directly on water samples or on the extracts of soil samples. The yield of extraction by different solvents (acetone, dioxane, ethanol and dichloromethane) was evaluated by the bioluminescent test. The measurements were carried out using a microplate format both for short time of contact (60?minutes, acute toxicity) and for longer time intervals (24 hours, chronic toxicity). The results have been expressed as percentage of inhibition with respect to the blank emission (100% emission). Original and treated samples have been analysed by gas chromatography to assess the hydrocarbons (C?>?12 and Poly Chlorinated Biphenyls, PCB) content. The autochthonous bacteria isolated from polluted samples proved less effective, due to the short time for selection in remediation activity with respect to the commercial ones, but their capacity to degrade long chain hydrocarbons was satisfactory. The presented laboratory study can be applied also in case of on-field conditions.     

Ultrasonication extraction coupled with magnetic solid-phase clean-up for the determination of polycyclic aromatic hydrocarbons in soils by high-performance liquid chromatography

C18-functionalized magnetic microspheres synthesized in a three-stage system and characterized by Fourier transform infrared (FTIR) spectroscopy and SEM were applied for clean-up and enrichment of polycyclic aromatic hydrocarbons (PAHs) in soil samples combined with ultrasonication extraction. Magnetic solid-phase extraction (MSPE) parameters, such as elution solvents, amounts of sorbents, enrichment time and organic modifier, were optimized together with ultrasonication time and extraction solvents. Under the optimal conditions, the developed method provided spiked recoveries of 63.2-92.8% with RSDs of less than 6.4% and limits of detection were 0.5-1.0 ng/g. This new method provides several advantages, such as high extraction efficiency, convenient extraction procedure and short analysis times. Finally, the method was successfully applied to the determination of polycyclic aromatic hydrocarbons in soil samples.     

The determination of volatile organic compounds in soils using solid phase microextraction with gas chromatography-mass spectrometry

Solid phase microextraction (SPME) was applied in the development of a protocol for the analysis of a number of target organic compounds in landfill site samples. The selected analytes, including aromatic hydrocarbons, chlorinated hydrocarbous, and unsaturated compounds, were absorbed directly from a headspace sample above a soil layer onto a fused silica fiber. Following exposure, the fiber was thermally desorbed in the injection port of the gas chromatograph and eluted compounds were detected using a mass selective detector. The stability and sensitivity of the extraction technique were examined at five temperatures (22–60°C) using a 100μm polydimethylsiloxane fiber. Calibrations, using soil samples spiked with selected solvents (0.5–30 μg/g), were linear; trichloroethene (r² = 0.992) and benzene (r² = 0.998). SPME was applied to the examination of a municipal landfill where 8 sites were sampled, at three depths, resulting in the detection of xylene (maximum 2.8 μg/g) and a number of other non-target organic contaminants.     

Using the tools of chromatography,mass spectrometry,and automated data processing in the detection of arson

The analysis of residual accelerants in fire debris is commonly carried out by a three-step procedure: sample preparation; separation and detection; and data interpretation. Each of these steps can be optimized individually but successful analysis requires that they are compatible with each other. The isolation of residual accelerant from fire debris requires that several methods are used to cover the range of fueis that are commonly used by arsonists. Since almost all incendiary fires are set with petroleum based fuels such as gasoline or heating oil, analysis is targeted toward hydrocarbons. Capillary column gas chromatography on apolar phases is now the overwhelmingly predominant method of separation. Data interpretation is commonly carried out by visual comparison of chromatograms. Fire debris analysis presents some unique challenges that are not often encountered in other fields. The analyte may be present at only trace levels and pyrolysis products from building materials or furnishings may dominate chromatographic patterns. Synthetic polymers may act as precursors to hydrocarbons that compete with substances typically found in petroleum based fuels. Exposure to heat and other environmental factors may also generate severe distortions in the chromatographic profiles of accelerants. Unfortunately, there is no simple solution to these problems. Methods are available to reduce some of the chemical noise introduced by interferences and thus enhance the recognizability of the target substances. Mass spectrometry, in combination with a modern data system, is the most effective approach to filter out unwanted substances. The interpretation of the analytical results is aided by scaling, side-by-side comparison, or stacking of chromatograms. An additional advantage of such computerized systems is the possibility of complete automation of the analysis. In this communication, we look at the interplay of chromatographic resolution, noise reduction by mass spectrometry, and automated data evaluation. Examples from model experiments and from simulated arson samples are presented.