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。     

闪蒸气相色谱法应用于天然纤维与助燃剂混合燃烧残留物的分析

应用闪蒸气相色谱法对2种火场中常见的天然纤维载体(木材和棉布)与汽油(或柴油)的混合燃烧残留物进行分析。在模拟火场条件下,分别制得2种载体与汽油或柴油混合燃烧的残留物。根据燃烧残留物热重分析结果选择闪蒸温度为300℃。分析对象为上述2种载体分别在无助燃剂和有助燃剂条件下共同燃烧得到的残渣,分别在完全燃烧后0,24,72h进行取样。结果表明:闪蒸气相色谱技术可从混合燃烧残留物中检测到助燃剂的特征组分,能够满足助燃剂检测鉴定的要求。随着取样时间的延长,助燃剂发生挥发,残留特征组分减少。棉布载体燃烧残留物比木材载体燃烧残留物对助燃剂特征组分的保留效果更好。柴油燃烧产物特征组分较汽油特征组分保留时间更长。     

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。     

火场PE、PVC检材助燃剂检测的研究

近年来汽油纵火案件逐年增多,国内外对助燃剂的检测也在不断发展~([1～4]).汽油残留物是案件定性和展开调查的重要依据,汽油易挥发、易燃烧,现代家庭高聚物较多,燃烧后成分复杂对检测造成很大干扰.     

热脱附气相色谱-质谱法快速分析助燃剂成分

建立了热脱附技术对火灾残留物中的助燃剂进行富集、浓缩后经气-质联用仪(GC-MS)分析的方法,并通过自动质谱去卷积定性系统对助燃剂谱库进行检索,汽油、柴油检测限分别为0.58 pl/mL和1.23 pl/mL.该方法简便、快速、准确.     

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。     

吸附萃取搅拌棒在火场空气中助燃剂残留物的采集取样中的应用

对微吸附采样技术进行改进,采用带有活性炭/聚二甲基硅氧烷涂层的长度为20mm的吸附萃取搅拌棒对火场空气中助燃剂残留物进行采集取样。将上述吸附萃取搅拌棒装于采集取样装置的前端,采集取样装置的后端与空气泵连接。在空气泵流量为50mL·min~(-1),采集时间为60s,采集温度为30℃的条件下进行采集取样。样品采集完成后,将吸附萃取搅拌棒直接放置于热分离进样杆中进样,对助燃剂残留物样品进行气相色谱-质谱法分析。当分析对象为汽油,采集时间为60s时,方法的检出限(5S/N)为0.1μL·L~(-1);当采集时间增加至300s时,检出限(5S/N)可降至1nL·L~(-1)。分析95~#汽油时,用AMDIS软件对总离子流色谱图进行分析,1μL·L~(-1)的汽油样品中检出400种特征化合物。除汽油外,还对航空煤油、柴油、乙醇和乙酸乙酯等助燃剂的残留物进行定性分析。     

固相微萃取-气相色谱-质谱法测定火场残留物中白酒类助燃剂北大核心CSCD

白酒主要指中国白酒。白酒是含乙醇较高的一种水溶性液体饮料,其主要成分是乙醇、水,极少的成分是酸、酯、醇、醛等有机化合物。白酒的种类繁多,乙醇含量较高的白酒有良好的燃烧性能,可被犯罪分子用来作为放火的助燃剂,因此目前对白酒类助燃剂的正确分析鉴定对于放火案件的侦破具有非常重要的意义。火场残留物中白酒类物质的提取和鉴定向来是火场助燃剂提取鉴定技术的难题。     

固相微萃取-气相色谱-质谱法测定火场残留物中白酒类助燃剂

正白酒主要指中国白酒。白酒是含乙醇较高的一种水溶性液体饮料,其主要成分是乙醇、水,极少的成分是酸、酯、醇、醛等有机化合物。白酒的种类繁多,乙醇含量较高的白酒有良好的燃烧性能,可被犯罪分子用来作为放火的助燃剂,因此目前对白酒类助燃剂的正确分析鉴定对于放火案件的侦破具有非常重要的意义。火场残留物中白酒类物质的提取和鉴定向来是火场助燃剂提取鉴定技术的难题。由于火灾现场通     

Methods for the determination of levoglucosan and other sugar anhydrides as biomass burning tracers in environmental samples – A review

Nowadays, there is a great pressure on finding an alternative source of energy. One such source is biomass combustion. Biomass is any organic matter such as wood, crops, seaweed, and animal wastes that during combustion emits energy but also smoke and solid residue. Biomass burning tracers, such as levoglucosan, mannosan and galactosan, are sugar anhydrides produced during burning of biomass that contain cellulose and hemicellulose. Analysis of environmental samples for tracers is the source of information about the type of biofuel burned. In this article, a literature review of the preparation and determination of biomass burning tracers for environmental samples was presented. The review discusses the preparation of different samples (particulate matter, soils, sediments, biological samples), extraction, derivatization, and determination. Amongst determination methods the most popular was gas chromatography with mass spectrometry but other techniques were also used, such as high‐performance liquid chromatography with aerosol charge detection, capillary electrophoresis with pulsed amperometric detection, and ion chromatography with pulsed amperometric detection.     

The Famous Amazonian Rosewood Essential Oil: Characterization and Adulteration Monitoring by Electrospray Ionization Mass Spectrometry Fingerprinting

Direct infusion of samples via electrospray ionization mass spectrometry (ESI-MS) is shown to characterize unequivocally genuine samples of Amazonian Aniba rosaeodora Ducke (Rosewood) essential oils obtained either from the wood or leafs. The ESI-MS also distinguishes the essential oils from synthetic linalool; hence, adulteration by the synthetic oil is also clearly detected. The analysis requires no pretreatment or preseparation, and the most polar components of the essential oil are extracted with an acidified 1:1 methanol/water solution. This simple extract is then analyzed by direct infusion ESI-MS in the positive ion mode, which provides characteristic fingerprintings of the sample composition. The ESI-MS fingerprinting can be used therefore as a simple and fast (few minutes) method for authenticity and quality control of this famous Amazonian essential oil.     

LF-NMR结合化学模式识别鉴别油脂种类及餐饮废弃油脂

应用主成分分析(Principal component analysis,PCA)和聚类分析法(Cluster analysis,CA)对9种(27个)常见食用植物油及100个餐饮废油的低场核磁共振(Low-field nuclear magnetic resonance,LF-NMR)(T2)弛豫特性数据进行分析。结果表明:在正常食用油种类区分方面,主成分分析的效果较优,9种食用油在主成分分布图上按种类正确分组,边界清晰。而在正常食用油与餐饮废油的区分方面,聚类分析效果较优,引入30个待测样本后,聚类分析(127个样品,欧式距离=5)的正确率为94.49%,分析误判率为5.51%,分组效果良好。LF-NMR结合化学模式识别可实现对油脂种类及餐饮废弃油脂的鉴别。     

基于~1H NMR指纹图谱结合多变量分析的地沟油检测方法

地沟油事件是中国近期发生的严重食品安全事故,而针对地沟油的检测目前尚无非常有效的方法报道.本研究对60种市售植物油和地沟油样品分别进行了核磁H谱测定,建立了12个鉴别指标,采用聚类分析技术对样品进行聚类分析,并将样品分为8大类,建立了判别函数.将未知样品的1H NMR数据代入判别函数,可检测和判别未知油的来源和品质.将该方法应用于两次盲测共69个样品,结果显示,两次盲测的正确率分别为91.9%和93.8%,可作为食用油品质检测的重要参考.     

Investigating a Range of Solid Samples by Automatic Water Sorption

The CISORP Water Sorption Analyser has been used to characterise a selection of solid samples at relative humidities from 0 to 100% and at ambient pressure. The analysis reveals many interesting features about the samples and shows the scope of the equipment. Hysteresis due to porosity and differences in the physical properties of similar chemical samples show up clearly in isotherm curves. Kinetic curves reveal features such as the level of stability of dehydrated food products, changes in the hydration states of salts, and the effect of adding powdered excipient on the water sorption behaviour of a pharmaceutical compound. Kinetic curves were also used to compare the water sorption behaviour of two types of wood found inside a pine cone, and to determine equilibrium moisture sorption by calculation. It was shown that many samples take up moisture irreversibly under the experimental conditions such as amorphous sucrose and other freeze-dried samples, as well as unstable crystalline forms of compounds. Wet samples such as soaked brick and archaeological wood from a well dry out irreversibly even at 100% RH. Recording isotherms at different temperatures allows the calculation of enthalpies of water sorption. If these are compared with the enthalpy of water condensation the two processes can be compared quantitatively. This revised version was published online in July 2006 with corrections to the Cover Date.     

傅里叶变换红外吸收光谱识别五种植物油的研究

以花生油、大豆油、芝麻油、棉籽油和米糠油为样品,采用傅里叶变换红外光谱仪,采集傅里叶变换红外吸收光谱,对光谱预处理后,提取红外特征信息,以1746cm-1和2855cm-1处的吸收峰面积比值为横坐标,1099cm-1处与1119cm-1处的吸收峰面积比为纵坐标,在Origin6.0上做出二维分布图,对各种油脂进行识别分析。结果显示,大豆油与其它4种油脂之间有明显区分;大豆油、花生油和芝麻油分布效果好,但棉籽油各样品点之间比较分散;能与其它油脂区分开的有以下几种分布花生油明显区别于芝麻油、棉籽油和大豆油;米糠油明显区别于棉籽油和大豆油。分布有交叉的油脂有米糠油与花生油或芝麻油有交叉,棉籽油与芝麻油有交叉。     

Electrospray ionization mass spectrometry and partial least squares discriminant analysis applied to the quality control of olive oil

Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)‐MS] is used to obtain fingerprints of aqueous–methanolic extracts of two types of olive oils, extra virgin (EV) and ordinary (OR), as well as of samples of EV olive oil adulterated by the addition of OR olive oil and other edible oils: corn (CO), sunflower (SF), soybean (SO) and canola (CA). The MS data is treated by the partial least squares discriminant analysis (PLS‐DA) protocol aiming at discriminating the above‐mentioned classes formed by the genuine olive oils, EV (1) and OR (2), as well as the EV adulterated samples, i.e. EV/SO (3), EV/CO (4), EV/SF (5), EV/CA (6) and EV/OR (7). The PLS‐DA model employed is built with 190 and 70 samples for the training and test sets, respectively. For all classes (1–7), EV and OR olive oils as well as the adulterated samples (in a proportion varying from 0.5 to 20.0% w/w) are properly classified. The developed methodology required no ions identification and demonstrated to be fast, as each measurement lasted about 3 min including the extraction step and MS analysis, and reliable, because high sensitivities (rate of true positives) and specificities (rate of true negatives) were achieved. Finally, it can be envisaged that this approach has potential to be applied in quality control of EV olive oils. Copyright © 2013 John Wiley & Sons, Ltd.     

Fast quantitative detection of sesame oil adulteration by near-infrared spectroscopy and chemometric models

Adulteration of foods has been known to exist for a long time and various analytical tests have been reported to address this problem. Among them, authenticity of sesame oil has attracted much attention. Near-infrared (NIR) spectral quantitative detection models of sesame oil adulterated with other oils are constructed by chemometric methods, i.e., competitive adaptive reweighted sampling (CARS), elastic component regression (ECR) and partial least squares (PLS). Sixty samples adulterated with different proportions of five kinds of other oils of lower price were scanned by a Fourier-transform-NIR spectrometer and the NIR spectra were collected in 4500–10000 cm⁻¹ region by transmission mode. All samples were divided into the training set and an independent test set. Model population analysis has also been carried out and confirms the importance of selecting representative samples. The experimental results indicate that the PLS model using only 10 variables from CARS and the ECR model show similar performance and both are superior to the full-spectrum PLS model. CARS focuses on selecting variables and ECR focuses on optimizing the parameters, implying that both roads lead to the same destination. It seems that NIR technique combined with CARS or ECR is feasible for rapidly detecting sesame oil adulterated with other vegetable oils.     

Chemical variability and antioxidant activity of Cedrus atlantica Manetti essential oils isolated from wood tar and sawdust

The present research was devoted to evaluating the effect of provenance and wood pyrolysis process on the phytochemical and antioxidant activity of essential oils extracted from sawdust and tar of Cedrus atlantica Manetti of Morocco. The essential oils were obtained by hydro-distillation from Cedar wood growing in two geographical locations of the Middle Atlas of Morocco (Senoual and Itzer forests) using a Clevenger-type apparatus and analyzed by Gas Chromatography-Mass spectrometry (GC/MS). Seventy compounds were approximately identified for each essential oil, accounting for 94% of the total oil’s composition, with the predominance of sesquiterpene hydrocarbons, where, α-himachalene (13.75%, 1.15%, 12.2%, and 16.69%) and β-himachalene (24.05%, 24.25%, 27.67%, and 44.23%) represented the major constituents in the four essential oils obtained. Multivariate analysis was used to discriminate the essential oils using principal component analysis (PCA) and Hierarchical Clustering Analysis (HCA). In addition, heatmap for dendrogram was used to investigate any correlation between the chemical profiles of each essential oil. Moreover, the antioxidant properties of the essential oils were studied using DPPH scavenging and Ferric Ion Reducing Power (FRAP). The results indicate that the essential oils from wood tar of Cedrus atlantica possess a strong antioxidant activity (IC₅₀ = 0.126 mg/mL and 0.143 mg/mL) in comparison with those from sawdust (IC₅₀ = 15.6 mg/mL and 16.3 mg/mL).     

Analysis of Peanut Oil Adulterated with Other Edible Oils by Spectrophotometry

Since peanut oil(PO) is more expensive than other seed oils, some PO is adulterated with other cheap seed oils, such as soybean oil, palm olein, cottonseed oil, corn oil and rapeseed oil. The conventional method for determining whether PO was adulterated is to detect the freezing point of oils. The proposed method for the determination of adulterants in PO was based on monitoring the change of absorbance when the sample was refrigerated. A special spectrophotometer was developed. A total of 10 kinds of POs from different suppliers were chosen and adulterated with other seed oils at the volume fraction levels ranging from 5% to 30%. A total of 150 samples were analyzed by the proposed method and the results were satisfactory.