全二维气相色谱分析直馏柴油中含硫化合物

采用全二维气相色谱-硫化学发光检测器,以直馏柴油为研究对象,考察了一维色谱柱初始温度、升温速率及两维柱温温差等条件对含硫化合物分离的影响,建立了直馏柴油中含硫化合物的分析方法。本方法对基质复杂的直馏柴油中含硫化合物的分离,并定性分析或归类了直馏柴油中的主要含硫化合物。以苯并噻吩为测试样,以峰面积对浓度作图,硫的浓度在1～100mg/kg范围内,峰面积与硫的浓度呈线性关系,相关系数大于0.999。与传统一维气相色谱相比,全二维气相色谱技术除可检测到苯并噻吩类、二苯并噻吩类等含硫化合物外,还可检测到直馏柴油中的硫醚类化合物;苯并噻吩类和二苯并噻吩类化合物也可得到较好分离。     

气相色谱-质谱法分析芥子气的氯氨消毒产物

用气相色谱／质谱法分析了芥子气的氯胺Ｔ、氯胺Ｂ的消毒产物。根据消毒剂和消毒产物的性质，研究了不同消毒液样品制备方法。探讨了消毒剂过量和不过量时对消毒反应的影响。     

吸热型碳氢燃料的结焦研究Ⅰ含硫抑制剂

在连续进样微反测焦系统上考察了二硫化碳、噻酚等含硫化合物添加前后碳氢燃料S-1裂解结焦速率的变化。结果显示,两种含硫抑制剂均可明显降低燃料裂解时的结焦速率,二硫化碳的抑制效果较好,可以使初始结焦速率降低90％。同时,气相色谱的分析结果显示,含硫抑制剂对燃料裂解产物的分布情况有一定影响,促进了烯烃选择性的提高,有利于改善燃料的吸热能力。利用扫描电镜以及元素分析手段对焦形态结构和元素组成的研究结果显示,含硫抑制剂还有利于改善焦的形态结构以及氢碳元素组成,对清焦工作有一定帮助。     

GC／MS分析煤抽出物中的含硫多环芳香化合物

煤的索氏抽出物中的含硫多环芳香化合物（ＰＡＳＨ）由硅胶柱色谱与配体交换薄层色谱（ＰｄＣｌ＿２／ＳｉＯ＿２）两步分离，用毛细管气相色谱（ＦＩＤ与ＦＰＤ）和色质联用仪分析其组成、结构。通过与文献的色谱保留指数相比较、质谱数据验证，鉴定出贵定煤含硫芳香化合物以三、四环结构为主，主要是二苯并噻吩及其Ｃ＿１～Ｃ＿３烷基取代物、苯并萘并噻吩及其烷基取代物，其它稠环含硫芳香化合物较少。     

搅拌棒萃取-热解吸气相色谱法测定水中倍半芥子气

建立了一种以SBSE萃取与热解吸-气相色谱-火焰光度法联用技术为基础的测定水中倍半芥子气的方法。对比了SBSE和固相微萃取(SPME)对水中的倍半芥子气的萃取回收率,实验结果表明,SBSE对倍半芥子气的萃取率在22.47%～22.60%之间,SPME对倍半芥子气的萃取率为0.4%。研究了萃取时间、解吸附时间、样品溶液pH值、萃取温度对萃取回收率的影响,选择萃取时间为20min、一级解吸时间为10min、二级解吸时间为4min、样品溶液pH值为7.0、萃取温度为25℃。检测倍半芥子气的线性范围为0.462～23.1μg/L,最低检出限为0.0924μg/L(S/N=3)。该方法已成功应用于河水的检测。     

芥子气过氧化物消毒产物的气相色谱-质谱测定

采用气相色谱-质谱(GC-MS)技术对芥子气的过氧化物消毒产物进行了分离和检测。不完全消毒定性检测到芥子气的6种氧化产物,未检测到其水解产物。增加消毒剂用量和延长消毒时间都会使消毒产物进一步氧化,最终变成二乙烯基砜、氯乙基乙烯基砜和芥子砜3种消毒产物。定量分析得出,1 mol芥子气生成的最终消毒产物分别为二乙烯基砜0.193 mol,氯乙基乙烯基砜0.145 mol,芥子砜0.504 mol。3种化合物线性范围1~30 mg/L,加标回收率在57%~78%之间,相对标准偏差小于3.1%,检出限均为0.5 mg/L。     

气相色谱法分析含硫恶臭物质综述

综述了含硫恶臭物质的气相色谱分析方法。详细介绍了目前分析含硫恶臭物质常用的采样及预处理方式、色谱柱和检测器,对不同的采样及预处理方式进行了比较。在预处理方面,可选择FTFE气袋、硅烷化苏玛罐采样,通过三级冷阱预浓缩后进样;或者采用Hayesep N、Tenax TA等吸附剂采样,热脱附进样。在分离方面,非极性柱、中极性柱可同时分离多种物质,应用范围较广;专用色谱柱有更好的分离效果。在检测方面,硫化学发光检测器(SCD)对含硫化合物有更高的选择性,线性关系好,检出限低,全二维气相色谱和飞行时间质谱联用具有更好的检测效果,但成本较高,操作复杂,难以推广。最后展望了未来的研究方向,为进一步优化分析方法提供参考。     

果蔬中107种残留农药的气相色谱-质谱检测方法

采用毛细管气相色谱-质谱法对果蔬中107种残留农药检测进行了系统研究,考察了被测组分在不同极性毛细管色谱柱上的保留时间值,对比了不同前处理技术对检测结果的影响,确定了气相色谱-质谱检测农残初筛离子选择原则,规定了气相色谱-质谱确证被捡出农药应符合的条件。     

利用大口径毛细管气相色谱法测定液化气中的含硫化合物

利用大口径毛细管色谱柱、不分流进样、氢焰离子化检测器（ＦＩＤ）、双火焰光度检测器（ＤＦＰＤ）,与气相色谱－质谱（ＧＣ－ＭＳ）联用技术相结合,对脱硫后的液化气进行测定,成功地鉴定出１７种含硫化合物。该法简便、快速,对含硫化合物的检测灵敏度高。     

化学发光技术在色谱柱后检测中的应用

化学发光与色谱联用具有选择性好、灵敏度高等优点,应用广泛.本文主要介绍近三年来化学发光包括鲁米诺、过氧草酸酯、Ru(bipy)33 、无机等体系作为液相色谱柱后检测及含氮、含硫化合物气相化学发光等体系作为气相色谱柱后检测的现状.     

甘草次酸及其衍生物的质谱研究

本文通过应用ＥＩ质谱和高分辨质谱对甘草次酸及其衍生物进行研究，阐明了分子离子的各种裂解、重排机理，讨论了主要离子的形成过程以及不同取代基对分子离子峰强度的影响。并用软电离手段──快原子轰击正、负离子（ＰＦＡＢ和ＮＦＡＢ）质谱，使ＥＩ谱上不出现分子离子峰的两个化合物而获得满意结果。     

Stereospecific fragmentation of starfish polyhydroxysteroids in electrospray ionization mass spectrometry

Electrospray ionization mass spectra and collision-induced dissociation mass spectra in positive and negative ion modes of five polyhydroxysteroid compounds from starfish were studied. Tandem mass spectra exhibit extensive fragmentation, including sequential neutral losses of H₂O molecules and cleavages in the tetracyclic nucleus and side chains. The relative intensity of some peaks in tandem mass spectra enables stereoisomers with the different orientations of the hydroxyl group at C15 in the tetracyclic nucleus to be distinguished. Some data on the fragmentation mechanisms were obtained by H–D exchange and mass spectrometry analysis.     

Spectral deconvolution for overlapping GC/MS components

The use of mass chromatogram peak centroids has been investigated as a means of deconvoluting the spectra of overlapping gas chromatography/mass spectrometry components. The peak centroids have been calculated with a precision of 0.04 scans (sd). This proved sufficient to allow deconvolution of the mass spectra belonging to two chemical components which were eluted 0.48 scans apart. For a more complex chromatography peak, it was possible to deconvolute the spectra of six components which were eluted within a 9 scan window. All the spectra produced by using this deconvolution mechanism agreed well with National Institute of Standards and Technology database spectra.     

A comparison of electron ionization mass spectra obtained at 70 eV,low electron energies,and with cold EI and their NIST library identification probabilities

Electron ionization (EI) mass spectra of 46 compounds from several different compound classes were measured. Their molecular ion abundances were compared as obtained with 70‐eV EI, with low eV EI (such as 14 eV), and with EI mass spectra of vibrationally cold molecules in supersonic molecular beams (Cold EI). We further compared these mass spectra in their National Institute of Standards and Technology (NIST) library identification probabilities. We found that

1. Low eV EI is not a soft ionization method, and it has little or no influence on the molecular ion relative abundances for large molecules and those with weak or no molecular ions.
2. Low eV EI for compounds with abundant or dominant molecular ions in their 70 eV mass spectra results in the reduction of low mass fragment ions abundances thereby reducing their NIST library identification probabilities thus rarely justifies its use in real‐world applications.
3. Cold EI significantly enhances the relative abundance of the molecular ions particularly for large compounds; yet, it retains the low mass fragment ions; hence, Cold EI mass spectra can be effectively identified by the NIST library.
4. Different standard EI ion sources provide different 70 eV EI mass spectra. Among the Agilent technologies ion sources, the “Extractor” exhibits relatively abundant molecular ions compared with the “Inert” ion source, while the “High efficiency source” (HES) provides mass spectra with depleted molecular ions compared with the “Inert” ion source or NIST library mass spectra.

These conclusions are demonstrated and supported by experimental data in nine figures and two tables.     

Comparison of electron ionization mass spectra of some organic compounds (MW < 200 Da) recorded on mass spectrometers of various types

Low-resolution electron ionization mass spectra recorded on various types of mass spectrometers (time-of-flight, quadrupole, and three-dimensional ion trap) were compared. A model mixture of 10 organic compounds (MW < 200 Da) was analyzed by gas chromatography-mass spectrometry. Pure mass spectra of analytes were extracted using the AMDIS software. The best repeatability was achieved for the time-of-flight mass spectrometer. The mass spectra recorded by a quadrupole and a time-of-flight mass spectrometer were quite similar. In the case of these instruments, library search using a commercial mass spectral data base (NIST’05) gave satisfactory result for each analyte (rank 1 or 2 in the “hit list”; Match > 900). In some cases, the mass spectra of model compounds recorded by the ion trap mass spectrometer differed in intensity of certain mass spectral peaks (but not in the set of peaks) from the mass spectra presented in the library and from the experimental mass spectra recorded by the time-of-flight and quadrupole instruments.     

Mass spectrometry studies of organolead compounds

The mass spectra of alkyl‐, aryl‐ and chlorinated ‐alkyl, aryl organolead compounds were investigated. Positive and negative ion mass spectra of these compounds were recorded using conventional electron impact conditions. In common with the analogous tetraalkyltin and tetraalkylgermanium compounds, tetrabutyllead produced no negative ion spectra under these conditions. The spectra were also examined by tandem mass spectrometry in order to establish reaction mechanisms for these compounds. Fragmentation patterns of seven organolead compounds, based on precursor–product ion relationships, are proposed. Copyright © 2001 John Wiley & Sons, Ltd.     

Software-based mass spectral enhancement to remove interferences from spectra of unknowns

Gas chromatography-mass spectrometry data from the analysis of complex environmental samples were converted into ASCII text and imported into a personal computer spreadsheet. A macro was written to perform mass spectral enhancement by statistical and mathematical procedures to separate the spectra of compounds of interest from interfering mass spectral responses, such as those of broadly eluting hydrocarbons. The extracted mass spectra were compared to reference spectra, with the result that usually 80–90% of the ions common to those in the reference spectra were successfully extracted by using this method. This procedure improved mass spectral quality and the ability of the data system to perform successful library searches. The fitted quality parameters showed systematic improvements after the data were subjected to the spectral enhancement procedures. These procedures could help to identify unknowns by separating their spectra from other signals, such as those of background aliphatic hydrocarbons.     

Charge-Reversal mass spectra of enolate ions of some open-chain and cyclic ketones for structure identification

The charge-reversal (CR) mass spectra of the enolate ions of heptanal and ten isomeric heptanones, of cyclohexanone, of cycloheptanone, of isomeric methylcyclohexanones, of isomeric ethylcyclohexanones and of the iso meric monoterpene ketones camphor, fenchone, pulegone and thujone were obtained by deprotonation using OH^? under chemical ionization conditions followed by collision of the [M ? H] ^? ions with helium in the second field-free region of a VG ZAB 2F mass spectrometer. The CR mass spectra were evaluated by similarity index (SI) values. Characteristic of the CR mass spectra of the open-chain enolates are fragment ions formed by α-cleavage. However, the CR mass spectra are dominated by peaks of small hydrocarbon ions, particularly in the case of cyclic and bicyclic enolates. The CR mass spectra of enolates of linear heptanones differing in the position of the carbonyl group can be easily correlated with the structure of the parent ketone. The CR mass spectra of enolates of isomeric heptan-2-ones differing only in the degree of branching of the alkyl group are similar, but can be distinguished by the SI values. The CR mass spectra of the enolates of the isomeric cyclic and bicyclic ketones studied are more or less identical and cannot be used for structural assignment.     

Nicotinates as derivatives for the mass spectrometric investigation of long chain alcohols

The mass spectra of the nicotinates of two methyl branched and one unsaturated long chain alcohol were compared with the mass spectra of the underivatized alcohols and of their trimethylsilyl ethers. It is shown that the structure of the chain is much more clearly shown by the spectra of the nicotinates than in the other spectra.     

Evidence for thermal decomposition contributions to the mass spectra of chlorinated phenoxyacid herbicides obtained by particle beam liquid chromatography mass spectrometry

The spectral quality of a group of chlorinated phenoxyacid herbicides has been shown to degrade under certain conditions upon introduction into the mass spectrometer by a particle beam interface. Experiments were performed to investigate these changes in spectra. Normalized ion chromatograms were generated for the herbicides, and the results showed a broadening of the profiles of some ions, indicating a longer residence time in the ion source. These ions were postulated as coming from the ionization of thermal degradation products from the herbicides. The generation of these ions was dependent on ion source temperature, analyte concentration, and, by implication, ion source cleanliness. Tandem mass spectrometry experiments were performed on these ions from the herbicides and ions from the corresonding phenols. The tandem mass spectra of the ions from the herbicides were similar to the tandem mass spectra of the ions from the phenols. Therefore, it appears that the particle beam mass spectra of the chlorinated phenoxyacid herbicides are composite spectra with contributions from the gas phase ionization of the parent herbidides and thermal decomposition products.