基于子空间重合判断的混合醇组分光谱识别方法

针对光谱分析中传统的特征峰比对法对物质定性检测存在的不足,采用基于子空间重合判断的混合光谱模式识别方法对9种混合醇组分进行定性检测。此法将测量到的待定性混合醇光谱信息视为向量,通过计算混合醇组分拉曼光谱与标准样品数据库拉曼光谱的子空间夹角,并依据子空间夹角变化,排列筛选出含有最少标准样品数目的子空间,该子空间所包含的标准样品组成即为待定性混合醇组分组成,从而成功实现了9种混合醇组分的定性识别,识别率100%。该法具有测试时间短、测试结果准确、与被测物含量无关、操作简便等优点,适用于多组分混合体系的定性识别。     

毛细管柱气相色谱法测定修正液中有害物质

应用带有电子捕获检测器的毛细管柱气相色谱法分析了修正液中的有害组分,用对测定无干扰的溶剂n-庚烷稀释修正液样品并测定了其中的5种对人体有害的氯代烃,即二氯甲烷、三氯甲烷、四氯化碳、1,1-二氯乙烷及1,1,1-三氯乙烷.方法的检出限(3S/N)在0.001～10.0 mg·kg-1范围内,相对标准偏差(n=6)在2.45%～3.01%之间,标准加入回收率在97.6%～104.0%之间.     

植物油中3种抗氧化剂的同时快速分析

建立了向量–子空间夹角判据结合紫外分光光度法测定植物油中3种抗氧化剂的方法,可用于植物油中特丁基对苯二酚(TBHQ)、丁基羟基茴香醚(BHA)、二丁基羟基甲苯(BHT)3种抗氧化剂的同时快速分析。采用紫外光谱–高效液相色谱(UV-HPLC)联用方法对植物油样品进行分离,构建不含待测组分的本底光谱数据库,基于向量-子空间夹角判据算法的步骤分析植物油中3种抗氧化剂的含量。实际样品加标回收率在95.2%~103.3%之间,RSD小于3%(n=6)。对市售15种植物油样品进行分析,其中12种植物油样品检出TBHQ,含量为21.34~30.12μg/m L,15种植物油样品均未检出BHA和BHT。方法适用于植物油中TBHQ,BHA和BHT 3种抗氧化剂的同时快速分析。     

斜投影-子空间夹角算法快速分析农药中阿维菌素

采用斜投影-子空间夹角算法快速分析农药中阿维菌素的含量。用斜投影算法从阿维菌素对照品中提取阿维菌素B_(1a)纯光谱数据,用子空间夹角判据计算农药中阿维菌素的含量。阿维菌素的质量浓度在4~14μg/mL范围内与用斜投影法提取的阿维菌素B_(1a)纯光谱吸光度呈良好的线性关系,相关系数r=0.9994。斜投影-子空间夹角算法加标回收率在98.80%~101.67%之间,测定结果的相对标准偏差小于2%(n=6)。用该方法与高效液相色谱法对同一样品进行测定,两种方法测定结果相接近,相对误差小于2.20%。该方法满足快速检测农药中阿维菌素含量的分析要求。     

阿司匹林合成体系三组分的拉曼光谱测定及应用

阿司匹林合成过程中所采集的阿司匹林、水杨酸和乙酸酐的拉曼光谱存在交迭现象,很难从光谱数据中分离各组分含量。根据反应体系的组成和浓度配制样本溶液并采集拉曼光谱,运用多种方法对光谱进行预处理结合偏最小二乘法（PLS）对混合体系中阿司匹林、乙酸酐和水杨酸3组分浓度和光谱矩阵建立回归模型,对回归结果进行比较,根据交互验证均方根误差RMSECV,预测相关系数帮,预测均方根误差RMSEP。结果表明预处理方案可以有效降低基线漂移对预测精度的影响,根据Q值检验法和严检验法确定经矢量归一＋Savitzky-Golay五点二次平滑一阶卷积求导＋均值中心化对拉曼光谱预处理,PLS主成分选4,交互验证选用“逐一法”可时阿司匹林反应体系3组分进行同时测定,此训练集为阿司匹林合成体系的拉曼光谱在线监测提供了良好的数据支持。     

基于主成分分析-Fisher判别分析的食品类塑料瓶物证差分拉曼光谱分类

食品类塑料瓶物证携带许多潜在证据信息,目前针对此类物证的检验研究尚处于探索阶段。利用差分拉曼光谱对46个食品类塑料瓶样品进行检验,依据样品材质及光谱特征峰可将样品分为三类。利用主成分分析（Principal component analysis, PCA）-Fisher判别分析,绘制主成分得分图,构建判别函数,建立分类模型。结果表明,食品类塑料瓶样品具有明显的聚类关系,原始分类与交叉验证分类准确率达到100 %。差分拉曼光谱结合PCA-Fisher判别分析,检验鉴别食品类塑料瓶物证具有一定的科学性。     

基于拉曼光谱成像的食品中化学添加剂的无损检测

基于拉曼光谱成像技术对小麦粉中过氧化苯甲酰和L-抗坏血酸进行快速、 无损、 原位检测, 并对2种添加剂的空间分布进行了可视化研究. 采用实验室自行搭建的线扫描式拉曼光谱成像系统, 激发光源波长为785 nm, 有效光谱范围为0~2885.7 cm^-1. 分别在小麦粉中添加含量为0.1%~30%的过氧化苯甲酰和L-抗坏血酸, 对制备的样品进行拉曼光谱扫描, 选取感兴趣区域的光谱信号进行平均, 得到平均光谱代表该样品的拉曼信息. 分别选取过氧化苯甲酰和L-抗坏血酸的2个特征峰, 与该物质在小麦粉中的含量建立线性关系, 其决定系数R²分别为0.9828 和0.9912. 采集的特征波段拉曼图像经过自适应迭代重加权惩罚最小二乘(airPLS)方法扣除荧光背景后, 选取合适的特征峰强度作为阈值, 对校正拉曼图像进行二值化分析, 得到添加物的空间分布可视化图像. 该方法与点检测拉曼技术相比, 具有检测结果准确且检测时间较短的优势, 且可以实现不均匀样品中多种物质的同时检测与分布可视化.     

基于小波-反向搜索及表面增强拉曼的食品中色素的光谱定性分析

使用金纳米粒子为增强因子的表面增强拉曼光谱技术,通过连续小波变换将拉曼光谱信号转化到小波空间(墨西哥帽小波作为小波基)。该步骤能够减轻信号中基线变化及随机噪音的影响并找到峰位置和最佳小波尺度系数。依据小波空间中的信息,对混合物光谱及标准谱光谱进行反向搜索得到反向搜索匹配系数(Reverse match quality,RMQ),作为判断混合物中目标成分是否存在的依据。该算法可对混合物中的目标物质进行准确定性,并已成功应用于多种食品中色素鉴定。食品中色素的检出率达到99%,且结果稳健,其效果明显优于传统的命中质量系数法(Hit quality index,HQI)。这证实了小波空间反向搜索方法是一种快速而准确的拉曼光谱定性算法。     

气相色谱-质谱法同时测定化妆品中18种氯代烃类有机溶剂

建立了同时测定化妆品中18种氯代烃类有机溶剂的气相色谱-质谱(GC-MS)检测方法。样品在饱和氯化钠溶液中由正十四烷振荡提取后,以Agilent J&W DB-624超高惰性毛细管柱(30 m×0.25 mm×1.4 μm)为分离色谱柱进行分析,以电子轰击(EI)源、SIM模式进行质谱监测,外标法定量。结果表明,18种化合物在19 min内完成色谱分离分析,检出限(LOD, S/N=3)和定量限(LOQ, S/N=10)分别为0.033~0.049 mg/L和0.10~0.15 mg/L, 18种氯代烃类有机溶剂在0.2~100 mg/L线性范围内线性关系良好,相关系数(R²)均不小于0.9992。以阴性样品口红(固体)和漱口水(液体)为样品基质,在不同添加水平下,18种氯代烃类有机溶剂的平均回收率分别为92.4%~103.1%和93.3%~102.4%,相对标准偏差(RSD, n=6)分别为3.1%~5.3%和2.8%~5.4%。采用该方法对115个化妆品样品进行测定,3个指甲油样品均检测出四氯乙烯,测定值为11.4~42.0 g/kg。研究建立的方法采用高沸点溶剂作为进样溶剂,取消溶剂延迟时间,使只能在溶剂延迟时间出峰的化合物得到有效色谱分离,分析时间短,且重复性好,灵敏度高,可同时检测各种化妆品中多种氯代烃类有机溶剂。该方法的建立为我国化妆品中氯代烃类有机溶剂检测标准的制订和质量安全监控提供了参考。     

红外光谱法结合主成分分析快速识别3种天然皮革

利用衰减全反射附件直接采集猪皮革、牛皮革和羊皮革等3种天然皮革的红外光谱图,分析了皮革氨基酸结构中主要基团的红外吸收峰的特点和位置。对光谱数据预处理后选择合适的光谱区域进行主成分分析,首先构筑主成分得分空间对样品直接进行判别,发现由于牛皮革样品和羊皮革样品的红外光谱图极为相似,它们的主成分得分空间区域大部分重叠在一起。然后以猪皮革、牛皮革和羊皮革等3种天然皮革样品作为3类组分,采用主成分回归方法建立相应的判别模型,3类组分的模型预测相关系数为0.965～0.990,均方差均不大于0.122,预测均方差均不大于0.213,模型具有较好的稳定性。利用检测集样品对模型进行验证,根据各组分的预测值可以快速方便地对3种皮革样品进行识别。     

Computer-assisted automatic peak recognition and result evaluation for analysis of chlorinated hydrocarbons in environmental samples

A data manipulation method has been developed for automatic peak recognition and result evaluation in the analysis of organic chlorinated hydrocarbons with dual-column gas chromatography. Based on the retention times of two internal standards, pentachlorotoluene and decachlorobiphenyl, the retention times of chlorinated hydrocarbons can be calibrated automatically and accurately. It is very convenient to identify the peaks by comparing the retention times of samples with the calibrated retention times calculated from the relative retention indices of standards. Meanwhile, with a suggested two-step evaluation method the evaluation coefficients and the suitable quantitative results of each component can be automatically achieved for practical samples in an analytical system using two columns with different polarities and two internal standards.     

Determination of chlorinated polycyclic aromatic hydrocarbons in water by solid‐phase extraction coupled with gas chromatography and mass spectrometry

Given the potential risks of chlorinated polycyclic aromatic hydrocarbons, the analysis of their presence in water is very urgent. We have developed a novel procedure for determining chlorinated polycyclic aromatic hydrocarbons in water based on solid‐phase extraction coupled with gas chromatography and mass spectrometry. The extraction parameters of solid‐phase extraction were optimized in detail. Under the optimal conditions, the proposed method showed wide linear ranges (1.0–1000 ng/L) with correlation coefficients ranging from 0.9952 to 0.9998. The limits of detection and the limits of quantification were in the range of 0.015–0.591 and 0.045–1.502 ng/L, respectively. Recoveries ranged from 82.5 to 102.6% with relative standard deviations below 9.2%. The obtained method was applied successfully to the determination of chlorinated polycyclic aromatic hydrocarbons in real water samples. Most of the chlorinated polycyclic aromatic hydrocarbons were detected and 1‐monochloropyrene was predominant in the studied water samples. This is the first report of chlorinated polycyclic aromatic hydrocarbons in water samples in China. The toxic equivalency quotients of chlorinated polycyclic aromatic hydrocarbons in the studied tap water were 9.95 ng the toxic equivalency quotient m^?3. 9,10‐Dichloroanthracene and 1‐monochloropyrene accounted for the majority of the total toxic equivalency quotients of chlorinated polycyclic aromatic hydrocarbons in tap water.     

Comparison of thermal degradation products from real municipal waste plastic and model mixed plastics

The thermal degradation of real municipal waste plastic (MWP) obtained from Sapporo, Japan and model mixed plastics was carried out at 430 °C in atmospheric pressure by batch operation. The chlorinated hydrocarbons found in PE/PP/PS/PVC [poly(ethylene)/poly(propylene)/poly(styrene)/poly(vinyl chloride)] degradation liquid products were also observed in PE/PP/PS/PVC/PET (poly(ethylene terephalate)) and MWP degradation liquid products. The presence of PET in MWP produced the additional chlorinated hydrocarbons, which are similar to the chlorinated hydrocarbons observed during the PE/PP/PS/PVC/PET degradation liquid products. In addition, the presence of PET facilitated the formation of more organic chlorine content in liquid products and drastic decrease in the formation of inorganic chlorine content.     

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。     

Real-time monitoring of monochlorinated benzene and polychlorinated biphenyls in the gas phase with on-line detection: High chemical selectivity of resonance-enhanced two-photon ionization.

The development of molecular spectroscopy has enabled us to select chlorinated aromatic hydrocarbons very rapidly. In particular, the laser ionization TOFMS (time-of-flight mass spectrometry) method is expected to be useful as an on-line, selective, and sensitive method. In the present work, real-time laser ionization TOFMS measurements were carried out on gaseous chlorinated aromatic hydrocarbons. The laser ionization method used resonance-enhanced two-photon ionization with the direct introduction of gas into the vacuum chamber. This method for analyzing aromatic hydrocarbons was developed using a pulsed supersonic molecular beam method. In the context of developing a highly selective and sensitive method, excitation of monochlorinated benzene at lambda = 263.07 nm was found to be effective in the wavelength region from 263 nm to 265 nm. Also the excitation of polychlorinated biphenyls at lambda = 266 nm was found to be substantially more effective than at lambda = 280, 300 or 320 nm. The achievable sensitivity for real-time (1 min) measurements using the laser ionization TOFMS technique was found to be in the ppbV range.     

便携式气相色谱-质谱联用仪现场测定畜禽粪便堆肥中挥发性有机物

采用便携式气相色谱-质谱联用仪进行了畜禽粪便堆肥排放气体中挥发性有机物质的现场分析.结果表明,在堆肥排放气体中可检测到含硫物质、脂肪烃、芳香烃及含氯有机物共20种物质.在已定量的8种物质中,CS2浓度最高,达到204 mg/m3;CS2和二甲二硫超过《恶臭污染物排放标准》(GB1455-93)的限值;SO2和苯超过《室内空气质量标准》(GB/T 18883-2002)的限值.本方法避免了常规检测中易出现的组分分解等问题,SO2测定值较常规方法提高59.3％.本方法操作方便,结果准确,适于对挥发性有机化合物的在线监测.     

Room temperature rate constants for the reaction of OH with selected chlorinated and oxygenated hydrocarbons

A study was conducted to measure the hydroxyl radical rate constants using a relative rate procedure in which the photolysis of methyl nitrite was the source of OH. During the course of this study, the OH rate constant was measured for a number of chlorinated solvents for which measurements have not previously been reported or for which there are few reliable measurements. Room temperature OH rate constants are presented for six chlorinated hydrocarbons (allyl chloride, benzyl chloride, chlorobenzene, epichlorohydrin, trichloroethylene, and vinylidene chloride) and four oxygenated hydrocarbons (acrolein, methacrolein, methyl ethyl ketone, and propylene oxide). Also included are OH rate constants for alkanes (ethane, propane, isobutane, and cyclohexane), alkenes (trans?2-butene and isoprene), and aromatic hydrocarbons (benzene, toluene, o^?, m^?, and p-xylene). Rate constants for compounds not previously reported include vinylidene chloride (1.49 ± 0.21 × 10^?11 cm³ molecule^?1 s^?1) and benzyl chloride (2.96 ± 0.15 × 10^?12 cm³ molecule^?1 s^?1). The analysis for chlorinated hydrocarbons included a correction for possible chlorine atom reactions.     

Adsorption/Thermal Desorption with Tenax-GC for the Collection and Analysis of Polycyclic Aromatic Hydrocarbons and Chlorinated Compounds

A system for the determination of polycyclic aromatic hydrocarbons(PAHs) and chlorinated compounds in air by means of adsorption/thermal desorption(ATD) with small bed volume (0.1 g) Tenax cartridges, followed by cryogenic trap in a U-shaped stainless steel tube with liquid nitrogen as an appropriate concentration method prior to capillary gas chromatography is described. Recoveries were determined for the complete ATD method. Desorption recoveries near 100% were found for a variety of chlorinated compounds and polycyclic aromatic hydrocarbons.