神府煤液化油加氢精制过程中硫氮化合物分布的变化

采用实沸点蒸馏对神府煤液化油及其加氢精制油做了馏分切割,并采用GC-PFPD与GC-NCD对液化油与精制油中的硫氮化合物类型进行了分析,研究了液化油加氢精制过程中硫氮化合物分布的变化。结果表明,液化油中硫含量随窄馏分的馏程由低到高呈现"U"型分布,氮的分布基本上随窄馏分沸点温度的升高而增大,氮的含量远高于硫的含量;经过固定床加氢精制后,97%的硫和98.9%的氮得到脱除。液化油中苯并噻吩和二苯并噻吩等二环和三环化合物占93.25%;经过加氢处理之后,硫醇、硫醚、噻吩类等低沸点含硫化合物基本消失,难脱除组分主要以苯并噻吩类、二苯并噻吩类为主。液化油中含氮化合物主要以五元杂环中性氮化物为主,占54.96%;碱性氮化物主要以苯胺类为主,占23.22%,喹啉类相对较少;经过加氢处理之后,脂肪胺类含氮化合物被完全脱除,精制油中残留的氮主要以碱性氮化物喹啉类与苯胺类含氮化合物存在。     

Three-component reaction of imidazoles,cyanophenylacetylene, and chalcogens: stereoselective synthesis of 3-alkenyl-2-imidazolethiones and -selones

The three-component reaction of 1-substituted imidazoles, cyanophenylacetylene, and elemental sulfur or selenium proceeds readily (for sulfur at room temperature without solvent, and for selenium in boiling MeCN) to stereoselectively afford 3-(Z)-cyanophenylethenyl-2-imidazolethiones or -selones in yields ranging 39–97% (for thiones) and 39–84% (for selones). In this reaction, tellurium is inactive both under the above conditions and upon heating (50–55 °C) in DMSO, instead, only the C(2)-vinylation of the imidazole ring in up to 98% yield takes place. The Z-stereoselectivity of the reaction is close to 100% (for sulfur) and reaches 91–99% (for selenium). The reaction involves the zwitterionic adduct of imidazoles with cyanophenylacetylene, which converts to the carbene via proton transfer (from the imidazole 2 position to the carbanionic site of the zwitterion) further reacting with chalcogens.     

Direct injection on capillary columns for gas chromatography

Discrimination may occur when injecting samples onto gas chromatography capillary columns, whereby peak areas for higher boiling point compounds are smaller than they should be compared to lower boiling compounds. This problem is most important in quantitative work on solutes having a wide range of volatility. An all-glass inlet system was used. Injections were made with a 10-μl syringe onto a column without and injection point heater and with the column oven about 20°C below the boiling point of the solvent used for the solutes. Discrimination did not occur in a range of C₁₂ to C₃₆ n-alkanes.     

Thermoanalytical characterization of polymers: A comparative study between thermogravimetry and evolved gas analysis using a temperature-programmable pyrolyzer

Evolved gas analysis (EGA) was carried out on 15 synthetic polymer samples using a temperature programmable pyrolyzer as a heating unit which was on-line coupled with a MS detector. A deactivated stainless steel tube and a vent free adapter were used to couple the pyrolyzer with the MS detector, and they were placed in a GC oven at 300°C to avoid condensation of evolved gases with high boiling point. Thermograms of polystyrene measured by this system (Py-EGA-MS) showed shifts of the peak temperature to the higher temperature region as the sample mass increased. It was found that the S/N ratios of EGA thermograms were 420-fold superior to those of differential thermogravimetry (DTG) thermograms for the same sample mass of 0.20 mg. Since a good linear relationship was obtained between peak temperatures obtained by Py-EGA-MS and DTG, it can be concluded that Py-EGA-MS can be used to obtain reliable data on thermal properties of samples with high sensitivity and using less sample.     

Quantitative analysis of phthalates using a pyrolyzer gas chromatography/mass spectrometry method

A pyrolyzer gas chromatography/mass spectrometry (GC/MS) method eliminates toxic solvents that burden our environment and can address the crucial problem of the solvent extraction GC/MS method. The purpose of this study is to establish an efficient quantitative analysis method for 10 phthalates that are regulated by the several governments. A change of concentrations over time for phthalates and internal standards was measured to verify the feasibility of using an auto sampler that facilitates analyzing multiple samples. Both standards maintained constant concentrations over the appropriate time for analysis. A certified reference material under the auspices of the Korea Research Institute of Standards and Science was used to verify the calibration curve obtained by the pyrolyzer GC/MS method, and a deviation was considered similar to the solvent extraction GC/MS method. Then, the limit of detection and limit of quantitation values were confirmed for various consumer products. To verify the reliability of the method, a comparative test with several accredited testing institutes was conducted, and the results were within the standard deviations of the results provided by the institutes. These results indicate that the pyrolyzer GC/MS method can be used in not only screening but also in accurate quantitative analysis.     

Recovery of some common solvents from protective clothing breakthrough indicator pads by microwave-solvent extraction and gas chromatography

The efficiency of solvent adsorption using Permea-Tec general solvent pads, used for the detection of chemical breakthrough of protective clothing, was determined for methanol, acetone, ethyl methyl ketone, trichloroethylene (TriCE), tetrachloroethylene (TetCE), toluene, m-xylene, and D-limonene. Known volumes of single or mixed solvents were added to pads in the range 0.2-5.0 microliters (0.16-8.13 micrograms). After microwave-solvent extraction (ME) into hexan-1-ol, the samples (0.5-3.0 microliters) of the filtered and extracted solutions were analyzed by gas chromatography. All solvents exhibited > 97% adsorption on the pads at spiking levels of 0.48-0.98 microgram for each solvent. The solvent recovery for the system was calculated for each solvent, with solvents with boiling points below 110 degrees C showing recoveries of > 90%, and with solvents with boiling points above 110 degrees C showing recoveries from 80 to 90%. The recovery precision was good (RSD < or = 4%) for all solvents over the range 1.0-2.5 microliters of applied solvents to pads for ME and 1.0 microliter of extracted solutions for GC analysis.     

铜绿微囊藻中磷酸腺苷的提取及分析

比较了酸提取、有机溶剂提取、MgSO4水溶液加热提取以及MgSO4水溶液加热超声波提取4种方式对磷酸腺苷(ATP、ADP和AMP)的提取效果,确定以MgSO4水溶液加热超声波提取效果最佳。采用MgSO4加热超声波提取时,2 mL提取液对ATP、ADP和AMP的提取效果较好。将ATP、ADP和AMP的混合标准溶液放于沸水浴中保温时,随着保温时间的延长,对ATP和AMP的影响较大,而对ADP的影响相对较小。实验结果证明,以MgSO4水溶液为提取液,用100℃加热10 min后,在超声波细胞粉碎机中超声破碎10 min的提取效率最高,既简单又无毒。用反相高效液相色谱等强度洗脱分离与紫外检测分析藻细胞中的ATP、ADP和AMP的含量,在较短的时间内(10 min)实现了较好的分离,分析准确而快速,是一较好的定性和定量分析方法。ATP、ADP和AMP的回收率分别为88%~97%、103%~107%和109%~115%,均在80%~120%之间,并且标准偏差和相对标准偏差均小于10%,证实了可以用加热超声波破碎提取,HPLC分析ATP、ADP和AMP的方法来提取和分析藻细胞中的ATP、ADP和AMP。     

Magnetic nanoparticles used in headspace extraction coupled with DSI-GC-IT/MS for analysis of VOCs in dry Traditional Chinese Medicine

A novel magnetic method using polystyrene modified magnetic nanoparticles to perform thermoheadspace extraction was successfully developed for extraction and preconcentration of volatile organic components in dry Traditional Chinese Medicine(TCM) based on gas chromatography-ion trap/mass spectrometry with a Chromato Probe direct sample introduction device. The dried fruit of Amomum testaceum Ridl. was used as the object TCM. The optimum parameters of headspace magnetic solid-phase extraction were investigated, in which desorption solvent ethyl acetate played a key role in this method,and the headspace extraction temperature of 90℃ and the headspace extraction time of 15 min finally decided. Headspace solid-phase microextraction method was also used to analyze volatile compounds in the TCM to compare with the proposed method. The results show that 60 components were identified totally by two methods; most of the low boiling point chemical compounds are isolated by this new method. In this work, an environmental-friendly and cheap analytical method was established, and a new approach to analyze volatile compounds in dry Traditional Chinese Medicine was also provided.     

白石湖煤液化粗油加氢精制过程硫、氮化合物转化规律

采用实沸点蒸馏仪对白石湖煤液化油进行馏分切割,切取<170℃液化粗油进行加氢精制脱除其中硫、氮化合物,采用硫化学发光气相色谱仪（GC-SCD）、氮化学发光气相色谱仪（GC-NCD）对液化粗油和精制油中硫、氮化合物进行分析表征,研究加氢精制过程硫、氮化合物的转化规律。结果表明,液化粗油中含硫化合物主要是噻吩类化合物和硫醇,经过加氢精制后基本消失,苯并噻酚类化合物脱除比例要低于噻吩类化合物,属于较难脱除含硫化合物。液化粗油中含氮化合物主要是苯胺类化合物,其次是吲哚类化合物,经过加氢精制吲哚类化合物全被脱除,苯胺和喹啉类化合物属于碱性含氮化合物,是精制油中残留的主要含氮化合物,含量达1.61 mg/kg。     

Ultrasound-Microwave Hybrid-Assisted Extraction Coupled to Headspace Solid-Phase Microextraction for Fast Analysis of Essential Oil in Dry Traditional Chinese Medicine by GC–MS

A novel one-step sample preparation technique termed ultrasound-microwave hybrid-assisted extraction coupled to headspace solid-phase microextraction (UMHE-HS-SPME) was developed in this study, which was used for the determination of essential oils in dry traditional Chinese medicine (TCM) based on gas chromatography–mass spectrometry. The dry roots of Angelica dahurica were used as the model TCM. In this work, ultrasound-assisted extraction was first combined with microwave-assisted extraction coupled to headspace solid-phase microextraction and applied to the rapid determination of A. dahurica. Sample preparations including isolation, extraction, and concentration of essential oils were performed in a single step. The effects of various parameters including fiber coating, ultrasound power, and irradiation time were investigated thoroughly and optimized. To further demonstrate the method’s feasibility, the conventional steam distillation (SD) method was used for the analysis of essential oils in the TCM to compare with the proposed method. The results show that more essential oil compounds were isolated and identified by UMHE-HS-SPME than by SD. Moreover, compounds with higher boiling point and many more oxygenated compounds were extracted from A. dahurica by the proposed method. In addition, the SD method required a long time (6 h) to isolate the essential oils, and large amounts of organic solvent for further extraction, while UMHE-HS-SPME needed only 10 min to prepare the samples, and no organic solvent. Relative standard deviation values less than 10 % show that the present method has good precision. According to the experimental results, the advantages of the proposed method are: short extraction time, high extraction efficiency, and solvent-free extraction. Thus, UMHE-HS-SPME is an alternative tool for fast analysis of essential oils in dry TCMs and can be potentially extended to other target analytes in dry matrix.     

Prediction of vapor pressures and enthalpies of vaporization of organic compounds from the normal boiling point temperature

Recently, our Laboratory proposed a model for the prediction of vapor pressures of organic compounds that requires only the knowledge of the normal boiling point of the compound involved, and a compound specific K_f for which generalized expressions for several classes of organic compounds as functions of the normal boiling point and the molecular weight were developed.In this work our model is compared with the one proposed in Lyman's book, which is similar to our model but uses different K_f values. The results indicate that our model provides very satisfactory results in the temperature range from the melting up to the normal boiling point and up to the critical, where no hydrogen-bonding is involved. Also, it is proven that the accuracy of our model is much better than that proposed by Lyman, especially for the high molecular weight compounds.Finally, our model is used for the prediction of enthalpies of vaporization at the normal boiling point. Excellent results are obtained that are comparable or better than those obtained with two recommended models in “The Properties of Gases and Liquids” book, where the latter, however, require as input information except from the normal boiling point the critical properties of the compound involved as well.     

Investigation of the storage stability of selected volatile sulfur compounds in different sampling containers

The suitability of various sample containers (i.e. standard Tedlar sample bags, black/clear layered Tedlar sample bags and Silcosteel sample cylinders) was examined for a gaseous multicomponent standard containing methylmercaptan, ethylmercaptan, dimethyl sulfide, ethylmethyl sulfide, 2-propylmercaptan, 1-propylmercaptan, 2-butylmercaptan, diethyl sulfide and 1-butylmercaptan (1 mg/m3 each in nitrogen). In the black/clear layered Tedlar sample bags, significant losses (up to 10% for methylmercaptan as the most critical component) were observed after 2 days, whereas in the standard Tedlar sample bags the recovery of methylmercaptan was approximately 90% even after 1 week. The Silcosteel sample cylinders were suitable for sampling of volatile sulfur compounds with respect to the stability of the analytes, but the recoveries exceeded 100% especially for the higher boiling compounds, which was attributed to enrichment effects on parts of the sampling system.     

Determination of Acrylamide and Acrolein in Smoke from Tobacco and E-Cigarettes

Acrylamide and acrolein are two short-chained hazardous compounds with neurotoxic, carcinogenic, and mutagenic effects. The aim of this paper is to describe a fast and simple procedure for simultaneous determination of both acrylamide and acrolein under standard conditions, suggest a suitable calibration protocol for custom analysis, and demonstrate its applicability to the analysis of gaseous products from, e.g., cigarettes, cigars, or electronic cigarettes. A gas chromatography–mass spectrometry (GC–MS) method was developed to quantify acrylamide and acrolein in smoke vapor from electronic cigarettes, tobacco cigarettes, and cigars. Nonionic and highly polar molecules with a low boiling point and molecular mass need a suitable derivatization method to achieve appropriate retention and selectivity on commonly used relatively nonpolar stationary phases and to enhance the molecular mass for easy MS detection. The derivatization of acrylamide and acrolein was carried out by a bromination method with elemental bromine. The dibromo derivatives were extracted into an organic solvent and following a dehydrobromination procedure the samples were injected into the GC–MS system. Important experimental parameters were varied, after which the bromination time was defined as 30 min, and the injector temperature and the starting temperature of gradient were set at 280 and 50 °C respectively. Acrolein was found in all tested samples, while acrylamide was detected only in smoke from normal tobacco. Possible mechanisms for the formation of these unsaturated compounds in the samples are discussed. After its validation the newly developed method was successfully and reliably applied to the analysis of both compounds. This short method provides an easy way to determine acrylamide and acrolein in gaseous samples.     

Splitless injection of up to hundreds of microliters of liquid samples in capillary GC: Part 1, concept

If a sample evaporates by flash vaporization in an empty injector insert, the solute material is well mixed with the expanding solvent vapors and the maximum injection volume is determined by the requirement that no vapors must leave the vaporizing chamber. If evaporation occurs from a surface (e.g., of Tenax packing), however, the solvent evaporates first. The site of evaporation is cooled to the solvent's boiling point, and the cool island formed in the hot injector retains solutes of at least intermediate boiling point (visually observed for perylene). Solvent vapors, free from such solutes, may now expand backwards from the injector insert and leave through the septum purge exit. When solvent evaporation is complete, the site of evaporation warms up, causing the high boiling solutes to evaporate and to be carried into the column by the carrier gas. The technique somewhat resembles PTV injection, but is performed using a classical vaporizing injector.     

Elution-extrusion counter-current chromatography separation of five bioactive compounds from Dendrobium chrysototxum Lindl

The elution-extrusion counter-current chromatography (EECCC) method was firstly developed by Berthod in 2003 and has been used in natural products separation in recent years. The advantages of this method have been well documented such as reducing the separation time and solvent consumption. In the EECCC method, the time point of the extrusion step is very important during the whole separation process as it directly affects the resolutions, separation time and solvent consumption. However, how to choose a suitable time point to perform the extrusion step without decreasing the resolution has not been studied yet. In the present study, a strategy for systematically calculating the time point for extrusion was developed in theory and five bioactive compounds from the extract of Dendrobium chrysototxum Lindl. were separated and compared using normal CCC and EECCC method. Our results demonstrated that the accurate time point to perform the extrusion could be calculated and reduced both separation time and solvent consumption without losing separation performance. Using this EECCC method, five bioactive compounds were separated and purified with high purity. The separation time and solvent consumption were decreased from 200 min to 100 min and 5-2.5L during the separation process while the resolutions were still acceptable. Finally, 63 mg, 48 mg, 97 mg, 162 mg and 43 mg of hydroxyl phenanthrenes and bibenzyls with the purity of 98.7%, 98.0%, 98.2%, 99.0% and 98.7%, respectively were isolated from 1.2 g crude extract of D. chrysototxum Lindl. initially purified by column chromatography in one step separation. The purities of compounds were determined by HPLC. Their structures were identified by electrospray ionization-mass spectrometry (ESI-MS) and NMR.     

Determination of highly volatile organic contaminants in water by the closed-loop gaseous stripping technique followed by thermal desorption of the activated carbon filters

Very volatile organic contaminants in water were determined by using closed-loop gaseous stripping combined with thermal desorption from the activated carbon filter into a high-resolution gas chromatograph. The operating parameters for quantitative applications were evaluated. The solvent-free thermal desorption procedure permits the determination of compounds that normally elute under the gas chromatographic solvent peak (e.g., dichloromethane and Freons). Sixteen volatile compounds with boiling points in the range -30 to 120 degrees C were determined with an overall recovery of 12-52%. Qualitative determinations of volatiles from a secondary sewage effluent were in good agreement with the results found by two more established methods.     

Advanced Methodologies for Adsorption/Thermal Desorption with Tenax-TA for the Analysis of Polycyclic Aromatic Hydrocarbons and Sulfur Compounds

We have evaluated an analytical method for the determination of polycyclic aromatic hydrocarbons (PAHs) and sulfur compounds in air by means of adsorption/temperature-programmed thermal desorption (ATPTD) with small bed volume (0.08g) Tenax-TA cartridges, followed by a cryogenic trap in a precolumn with liquid nitrogen as an appropriate concentration method before capillary gas chromatography is described. The enriched components from the adsorption cartridges are transferred to the capillary column with a valveless switching system. Recoveries were determined for the complete ATPTD method. Desorption recoveries near 100% were found for various of polycyclic aromatic hydrocarbons and sulfur compounds. The sulfur compounds known to cause nuisance odors in the atmosphere near sulfur recovery and sewerage treatment works were also determined.     

Prediction of the molar volume at the normal boiling point

A group contribution method for the prediction of the molar volume at the normal boiling point has been developed. The method can be used for organic and inorganic compounds. It cannot be used for elements and diatomic molecules. Group contributions are shown for a wide variety of hydrocarbons, organic halogen compounds, organic oxygen compounds, organic nitrogen compounds, organic sulfur compounds, organic boron compounds, organic silicon compounds, miscellaneous organics, and many inorganic compounds.Contrary to the corresponding states methods for the prediction of molar volumes, knowledge of critical properties, acentric factors, and reference volumes is not needed.     

Synthesis of indium nanoparticles: digestive ripening under mild conditions

Here we report the synthesis of monodispersed indium nanoparticles by evaporation/condensation of indium shot using the solvated metal atom dispersion (SMAD) technique, followed by digestive ripening in low boiling point (BP 38 °C) methylene chloride and in a high boiling point (BP 110 °C) toluene solvent. The as-prepared SMAD indium nanoparticles are polydispersed with particle size ranging from 25 to 50 nm, but upon digestive ripening (heating of colloidal material at the boiling point of solvent in presence of excess surface active ligands) in methylene chloride, a remarkable reduction of particle size was achieved. In higher boiling solvent (toluene), where the indium nanoparticles at reflux temperature are probably melted, it does not allow the best result, and less monodispersity is achieved. We employed different surface active ligands (amine, phosphine, and mixed ligands) to passivate these indium nanoparticles. The temporal evolution of the surface plasmon of indium nanoparticles was monitored by in situ UV-vis spectroscopy, and particles were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The merits of this synthesis procedure are the use of bulk indium as starting material, tuning the particle size in low boiling point solvent, particle size adjustment with the choice of ligand, and a possible scale up.     

Application of high-temperature simulated distillation to the residuum oil supercritical extraction process in petroleum refining

The gas chromatographic method of high-temperature simulated distillation (HTSD) is described, and the results are presented for the application of HTSD to the characterization of petroleum refinery feed and products from solvent deasphalting operations. Results are presented for refinery residual feed, deasphalted oil, and asphaltene fractions from the residual oil supercritical extraction process. Asphaltene removal from petroleum residuum using solvent deasphalting results in the improved quality and high recovery of deasphalted oil product for use as lube oil, fluid catalytic cracking, or hydrocracker feedstocks. The HTSD procedure presented here proves valuable for characterizing the fractions from the deasphalting process to obtain the percentage yield with boiling point data over the range from approximately 36 degrees C (97 degrees F) to 733 degrees C (1352 degrees F), which covers the boiling range of n-paraffins of carbon number C5 to C108.