叔丁醇气相脱水生产异丁烯反应热力学分析

研究了叔丁醇(TBA)气相脱水生成异丁烯过程所涉及主、副反应的热力学,采用平衡常数计算法得出主、副反应在不同温度下的标准摩尔焓变、标准摩尔生成吉布斯自由能变和标准平衡常数等热力学数据。采用吉布斯自由能最小化法,从热力学角度讨论了反应温度、压力、惰性稀释和水蒸气稀释对TBA脱水反应的影响规律,可为工业化TBA脱水工艺开发提供借鉴。热力学分析结果说明了TBA脱水反应易在高温低压下进行,异丁烯平衡产率对温度和压力的变化更为敏感,TBA原料含水量对异丁烯平衡产率几乎无影响,以热力学角度而言,无需对TBA原料进行干燥处理。     

短链氯化石蜡的研究进展

短链氯化石蜡(SCCPs)是一类碳原子数为10~13的正构烷烃氯化衍生而成的复杂混合物,具有环境持久性、生物蓄积性和生物毒性,可长距离迁移。作为《关于持久性有机污染物的斯德哥尔摩公约》拟增列持久性有机污染物(persistent organic pollutants,POPs)之一,短链氯化石蜡的生物毒性、环境和人体健康风险及环境污染现状等的研究备受关注。本文概述了SCCPs的物理化学性质;详细比较了国内外对SCCPs的分析方法的优缺点,包括气相色谱-电子捕获检测器(GC-ECD)、气相色谱-电子轰击串联质谱(GC-EI/MS)、气相色谱-低分辨电子捕获负化学离子源质谱(GC-ECNI-LRMS)等;重点综述了SCCPs在全球环境介质(大气、土壤、底泥、水)及生物体中的污染现状;总结了SCCPs现有的污染控制技术,包括生物降解、光降解、吸附等;同时,针对目前存在的问题,对SCCPs今后的研究方向进行了展望,以期为该领域相关的研究工作提供参考。     

Investigation of nitrogen compounds in coal tar products. 1. Unfractionated materials

The direct application of gas chromatography (g.c.) with a nitrogen-selective alkali-flame detector (AFD) and mass spectrometry to the identification of nitrogen compounds in coal tar products without the need for prior separation of nitrogen-rich fractions is described. Accurate mass measurement has allowed the assignment of atomic compositions to many nitrogen heterocycles despite their presence as minor components in complex aromatic mixtures, but some interference from hydrocarbons was encountered. Boiling point characteristics were used to assist in distinguishing between the various possible isomeric compound types. The AFD was used successfully for the quantitative g.c. determination of a range of nitrogen heterocycles in the unfractionated samples.     

Detection of hydroxy fatty acids in biological samples using capillary gas chromatography in combination with positive and negative chemical ionization mass spectrometry

The most common method for use in the structural analysis of hydroxy fatty acids in biological samples is the gas chromatography-mass spectrometry (GC-MS) analysis of trimethylsilyl ethers of the methyl esters using electron impact ionization. A comparison of electron impact (EI) with chemical ionization mass spectrometry (CI-MS) shows that CI-MS is the superior technique. All ions necessary for structural analysis are observed at sufficiently high levels of intensity when methane or isobutane are used as reactant gases. The molecular weight can be determined from the ion group M+H, M-15 and M+H−90. The ionic series M+H−n×90 enables one to determine the number of hydroxyl groups. The position of the hydroxyl groups can be derived from the fragments of the α-cleavage of the fatty acid chain. The application of heptafluorobutyrates as derivatives for hydroxy fatty acid methyl esters shows advantages in the trace analysis of these compounds. Heptafluorobutyrates exhibit useful mass fragmentation patterns in the positive as well as in the negative CI mode. With methane as the reactant gas, M+H usually is base peak in positive mass spectra. The ionic series M+H−n×214 leads to the number of hydroxy groups in the molecule. In the negative mass spectra, M and M-20 are indicative for the molecular weight. The ion group m/z 213, 194 and 178 at high levels of intensity is typical for heptafluorobutyrates. The advantage of the application of heptafluorobutyrates is the high sensitivity which can be obtained in trace analysis using negative MS. Heptafluorobutyrates of hydroxy fatty acids gave a 20-fold higher response in the negative scan mode compared to that of the positive. The detection limit for heptafluorobutyrates in negative CI-MS was on the order of 1 fg (10⁻¹⁵ g).     

Screening of Aerosol Filter Samples for PAHs and Nitro-PAHs by Laser Desorption Ionization TOF Mass Spectrometry

Direct and selective screening of aerosol particulate matter for polycyclic aromatic hydrocarbons (PAHs) and nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) is achieved using laser desorption ionization time-of-flight (LDI TOF) mass spectrometry. Desorption and ionization of collected aerosol particulate matter was accomplished using pulsed UV radiation at 266 nm. PAHs were detected in positive ion spectra, while nitro-PAHs were selectively detected in negative ion spectra. Direct laser desorption ionization circumvents extraction procedures necessary for HPLC or gas chromatography/mass spectrometry (GC/MS) analyses, and such screening offers potential cost saving by identifying samples which contain too little PAH for GC/MS analyses to be productive. Applicability of the LDI TOF method was demonstrated by collecting aerosol particles of less than 2.5 mu m aerodynamic diameter (PM 2 . 5) on Teflon filters from inside an urban bus terminal. Sampling of small air volumes (0.32-0.98 m3) was sufficient for LDI TOF analysis. Positive ion mass spectra of all collected aerosol samples exhibited peaks attributed to a wide range of PAHs. Of primary importance, selective ionization and detection of less abundant and more toxic nitro-PAHs is demonstrated in the negative ion spectra. GC/MS analyses of duplicate filters confirmed laser desorption ionization analyses and assisted identification of specific PAH isomers.     

Monitoring the products and kinetics of oil shale pyrolysis using simultaneous nitrogen specific and flame ionization detection

The use of the thermionic nitrogen specific detector (TSD) and flame ionization detector (FID), in conjunction with gas sampling and capillary column g.c. is described as a means of following the thermal degradation of involatile substances containing organically bound nitrogen. The response of the TSD to a range of nitrogen compounds is shown to be approximately proportional to nitrogen content in most instances. Application of this method to a study of oil shale pyrolysis reveals that nitrogen compounds are evolved more rapidly than hydrocarbons.     

毛细管柱气相色谱法快速测定水中11种痕量氯苯类化合物

采用毛细管柱气相色谱定量法同时测定水中11种痕量氯苯类化合物的方法。石油醚萃取富集水中氯苯类化合物,用电子捕获检测器检测,整个分析过程只需25min,检出限可达0.001~0.01μg·L-1,均都低于GB/T5750.8-2006,每种化合物的回收率在80%~105%,相对标准标准偏差在1.5%~4.5%之间。     

A sensitive method for the determination of carbonyl compounds

2,4,6-Trichlorophenylhydrazine was tested as a reagent for carbonyl compounds. As little as 0.1 of the 2,4,6-trichlorophenylhydrazones (2,4,6-TCPH) could be measured with an electron capture detector, so this reagent should be useful in measuring the carbonyl compounds in oxidized fats at levels near their flavor thresholds. Mixtures of 2,4,6-TCPHs were separated by thin layer chromatography. Alkan-2-one-2,4,6-TCPHs were separated from aldehyde-2,4,6-TCPHs on alumina plates. The alkanal, alk-2-enal and alk-2,4-dienal-2,4,6-TCPHs were separated from each other either on silica gel plates or silica gel-silver ion plates. The derivatives within each carbonyl class were separated by chain length on chromatography media impregnated with phenoxyethanol. The 2,4,6-TCPHs eluted from thin layer plates were determined with an electron capture detector after gas chromatography on a 30 cm column of freeze-dried detergent base coated with a silicone oil. Journal Paper No. J-6842 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, project No. 1856.     

Massenspektroskopie von Thiogibberelllnen

Mass Spectroscopy of Thiogibberellins . The results of the positive ion (electron impact, desorption electron impact, low voltage electron impact, positive ion desorption chemical ionization, — EI, DEI, LEI, PIDCI), as well as negative ion (electron attachment — EA) mass spectra of 4 different types of thio gibberellins 6–9 are compared, and the fragmentation pathways are discussed.     

Ionization efficiency of evolved gas molecules from aerosol particles in a thermal desorption aerosol mass spectrometer: Laboratory experiments

Thermal desorption aerosol mass spectrometers (TDAMSs) with electron ionization are widely used for quantitative analysis of aerosol chemical composition, and the ionization efficiency of evolved gas molecules from aerosol particles is an important parameter for such analysis. We performed laboratory experiments using a custom-made TDAMS to investigate the key factors affecting ionization efficiency. Ammonium chloride (NH₄Cl) and ammonium iodide (NH₄I) were used as test compounds because their thermal decomposition products are expected to be simple (dominated by ammonia (NH₃) and hydrogen halide (HX)). The ion signals originating from NH₃ and HX were measured by altering the position of the ionizer relative to the vaporization point. The ratio of ion signal from NH₃ to that from HX increased with increasing divergence angle of evolved gas plumes, which suggests that the angular distribution of gas molecules could be an important factor affecting the ionization efficiency.

Copyright © 2018 American Association for Aerosol Research     

Quantification of Pentafluorobenzyl Oxime Derivatives of Long Chain Aldehydes by GC–MS Analysis

Negative ion mass spectrometric techniques, for compounds having good ionization properties, such as pentafluorobenzyl derivatives, are believed to be more sensitive than positive ion methods. Preparation of PFB oximes of fatty aldehydes from crude lipid extracts is problematic due to the release of free aldehydes from plasmalogens during derivatization. Accordingly, in these studies plasmalogens were removed by silicic acid column chromatography prior to pentafluorobenzyl derivatization. This simple purification step to remove plasmalogens is shown to facilitate the quantification of long-chain aldehydes by analysis of their pentafluorobenzyl oxime derivatives utilizing gas chromatography–mass spectrometry in the negative ion chemical ionization mode. The limit of detection for long chain fatty aldehydes using this method is 0.5 pmol and it is linear over two orders of magnitude. Silicic acid column chromatography followed by electrospray ionization mass spectrometry demonstrated that plasmalogens were removed (the detection limit for this analyses was ≤0.3 pmol). Furthermore, we have exploited the utility and sensitivity of this method to identify increases in hexadecanal and octadecanal in 3-amino-1,2,4-triazole treated human neutrophils. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Detection of Military Explosives by Atmospheric Pressure Chemical Ionization Mass Spectrometry with Counter‐Flow Introduction

To detect vapors from explosives, we have developed a new detection system based on a novel ion source for atmospheric pressure chemical ionization (APCI). The direction of the sample gas flow introduced into the ion source is opposite to that of the ion flow produced by the ion source. We call this technique “counter‐flow introduction” (CFI). The CFI ion source has high ionization efficiency for nitro‐compounds and is installed in an ion‐trap mass spectrometer. Our tests on various military explosives show that this system is suitable for practical on‐line explosive detection; namely major explosives can be detected within a few seconds without any pretreatment of the sample gases.     

Sanfte Ionisierungsmethoden zur massenspektrometrischen Analyse von Tensiden

Soft Ionization Methods for the Mass Spectrometric Analysis of Surfactants The analysis for cationic, nonionic and anionic surfactants by means of soft ionization mass spectrometry is described. Using Direct Chemical Ionization and Fast Atom Bombardment the positive and negative ion mass spectra give molecular weight and structural information. If Fielddesorption is not available, Fast Atom Bombardment is the method of choice for ionics. It is shown, that Direct Chemical Ionization is well suited for the analysis of thermolabile nonionics e. g. sugar derivatives. In the negative ion mode molecular weight information of even anionics is available without chemical pretreatment. For the evaluation of the molecular weight distribution Fast Atom Bombardment Mass Spectrometry results are compared to a conventional gas chromatographic method. By the mass spectrometric method a time consuming sample preparation is not necessary.     

气相色谱检测器进展

热导检测器（ＴＣＤ）、火焰电离检测器（ＦＩＤ）、电子俘获检测器（ＥＣＤ）、氮磷检测器（ＮＰＤ）、光电离检测器（ＰＩＤ）和火焰光度检测器（ＦＰＤ）是气相色谱常用的六种检测器。本文对近年来这些检测器在其结构、体积和电路等方面的改进,以及在灵敏度、选择性和线性范围等方面的提高,作了综述。     

气相色谱法测定地下水中2,4-/2,6-二硝基甲苯

新建一种测定地下水中2,4-和2.6-二硝基甲苯的液液萃取-气相色谱法。甲苯作溶剂萃取水中的2,4-和2.6-二硝基甲苯,经DB-1701色谱柱分离,电子捕获检测器(ECD)检测。经过优化的色谱方法测定结果显示,2,4-和2.6-二硝基甲苯的检出限都为0.05μg/L,均具有较好的线性关系,相关系数都大于0.999;2,4-和2.6-二硝基甲苯的精密度分别为3.4%～12.6%和4.0%～15.5%;2.4-和2,6-二硝基甲苯的加标回收率分别是75.4%～126.0%和71.5%～122.6%。本方法准确、灵敏、快速,可为地下水样中2,4/2,6-二硝基苯的污染评价提供技术支持。     

Separation and characterization of large-ring number polycyclic aromatic hydrocarbons in non-distillable, pyridine soluble coal-liquids

Low-pressure liquid chromatography, high-performance liquid chromatography, and field ionization mass spectrometry (f.i.m.s.) were used to obtain compositional information on large-ring number polycyclic aromatic hydrocarbon (PAH) present in a non-distillable coal liquid sample. A highly selective h.p.l.c. method for the separation of (PAH) from polar compounds was applied to nitrogen-compound fractions derived from a Wyodak non-distillable ( > 427 °C) coal-liquid sample. F.i.m.s. analyses revealed that the PAH subfractions isolated by the h.p.l.c. procedure contained large-ring number PAH and relatively few nitrogen compounds. The methods developed can generally be applied to the analyses of complex organic mixtures, and in conjunction with other methods, can yield detailed polycyclic aromatic hydrocarbon compositional information.     

Relative Genotoxicities of PAH of Molecular Weight 252 AMU in Coal Tar-Contaminated Sediment

Bioassay-directed chemical fractionation methodology was used to calculate relative mutagenic potencies of polycyclic aromatic hydrocarbons (PAH) of molecular weight 252 amu in coal tarcontaminated sediment from Sydney Harbour, Nova Scotia. A normal phase HPLC technique was used to separate organic solvent extracts into fractions containing isomeric PAH of a single benzologue class. Bioassays with Salmonella typhimurium strain YG1025 with the addition of oxidative metabolism (S9) showed that approximately 50% of the mutagenic activity observed in the sediment extract was associated with PAH of molecular weight 252 amu. Further separation of the 252 PAH fraction using reversed phase HPLC yielded subfractions containing individual compounds; bioassay dose-response curves for these subfractions showed that benzo[a]pyrene was responsible for approximately 75% of the activity of the 252 PAH fraction.     

Analysis of Polycyclic Aromatic Hydrocarbons in Egyptian Petroleum Condensate Oils

The polycyclic aromatic hydrocarbons (PAH) in Egyptian condensates are analyzed for the first. A solid phase extraction (SPE) followed by gas chromatography-mass selective detection was used for their analysis. The method was calibrated for optimal extraction conditions. Excellent recoveries were found (78–114%) for the PAHs that were identified using a variety of standards and GC-MS spectra. The solid-phase extracted PAH fraction was further separated by HPLC on a Ag(I) mercaptopropanosilica gel to reduce the complexity of the sample by separating the PAHs based on the number of aromatic rings. The analytes were quantified using GC with a flame ionization detector. For this kind of sample SPE is a more convenient separation technique than an open column. PAHs containing two to four rings in the concentration range 0.6–11 μg/L were measured. Some preliminary geochemical hypotheses based on the analyzed PAHs and the previously analyzed S-containing aromatic compounds were formed as to the depositional environment and source rock type.     

Thermal decomposition processes in aromatic amine-based polybenzoxazines investigated by TGA and GC-MS

Three different aromatic amine-based polybenzoxazines are subjected to thermal decomposition in a thermogravimetric analyzer. The degradation products, which are volatile compounds evaporating out of the furnace as gases, are trapped and analyzed further by a gas chromatograph which is coupled with a mass selective detector (GC-MS). All the degradation products are separated by GC and come out at different retention times, as seen in the total ion chromatogram. All the compound's mass are selectively identified by MS. The chromatograms are divided into two regions; the low column temperature region containing low molecular weight and highly volatile compounds, and the high column temperature region containing higher molecular weight and less volatile compounds. The evolved gas analysis performed by GC-MS allows us to identify the molecular weight and also the structure of the volatiles. This information is then used to illustrate the processes occurring during the thermal decomposition of aromatic amine-based polybenzoxazines.     

Spectroscopic investigations of solvent-refined coal fractions

The chemical characteristics of Amax solvent-refined coal are investigated on a molecular size and component basis. Gel permeation chromatography (g.p.c.) is used to characterize the tetrahydrofuran-soluble portion of the SRC and to obtain the molecular size distributions, and is also used as a preanalysis step, in which fractions are obtained according to elution time. The THF-soluble portion of the SRC has elution times comparable to asphaltene plus oil. The resultant g.p.c. eluent is divided into six fractions, three of which have molecular sizes and elution times comparable to asphaltene alone, two to oil, and one to asphaltene plus oil. These observations are confirmed by chemical ionization and electron impact mass spectrometry. Various analytical techniques are used to establish further the composition of the fractions, including: infrared spectrometry, elemental analysis, flourescence excitation and emission spectrometry, high-pressure liquid chromatography and gas chromatography.