不同碳链临界正烷烃对孔道中甲醇作用的Monte Carlo模拟

利用Monte Carlo(MC)方法考察了烷烃的分子尺寸与介质孔道尺寸对孔道中甲醇脱附和萃取的影响.研究表明,随孔道尺寸的增加,不同碳链的正烷烃(C5~C8)对甲醇脱附作用受孔尺寸的影响在逐渐减小;孔道尺寸不同对正烷烃萃取能力的影响程度也不相同.     

溶剂对丙烯环氧化反应活性的影响

研究了溶剂对钛硅分子筛催化丙烯环氧化反应的影响．研究结果表明，随着溶剂极性增加，活性中间过渡态中的过氧键越易断裂，容易把氧原子传递给丙烯，因此丙烯环氧化反应活性增加．由于TS—1催化剂孔道狭小，产生空间位阻效应，醇溶剂分子越大，活性中间过渡态的形成越困难，反应活性越低．甲醇-丙醇混合溶剂中丙酮含量小于50％时，反应活性与纯甲酵做溶剂相近；混合溶剂中丙酮含量增加到80％时，反应活性略降低；丙酮含量进一步增加，反应活性急剧下降．     

分子烙印聚合物作超临界流体萃取后处理用固体吸附剂

利用离线超临界流体萃取与高效毛细管电泳相结合，分析了标准添加样品中的除草剂（2，4－二氯苯氧乙酸（2，4－D）），探讨了温度、压力和改性剂对萃取的影响，考察了在不同条件下合成的2，4－D为烙印分子的子烙印聚合物对2，4－D在不同极性溶剂中的吸附能力，并将分子烙印聚合物作为超临界流流体萃取后处理用固体吸附剂，结果表明，在甲醇和水的混合极性溶剂中制备的分子烙印聚合物对提高分析选择性的效果最佳。     

离线超临界流体萃取和气相色谱/质谱联用对实验室内空气中气相有机污染物的测试

通过团体吸附剂富集，再用超临界ＣＯ２脱附后用气相色谱及质谱技术对实验室内空气中气相有机污染物进行了考察。文中对采样和萃取条件进行了优化，并与热脱附所得结果做了比较。结果表明在２２ＭＰａ，８０℃时，用甲醇改性的超临界ＣＯ２进行萃取的结果优于热脱附法。该法鉴定出气相有机污染物中５２个组分，占色谱峰总面积的９９．６％。     

一种改进的SPME方法提取火场残留物中的促燃剂

对当前国内外用于火场残留物中促燃剂的提取方法进行研究,包括采用活性炭片法(ACS)、固相微萃取(SPME)以及对固相微萃取技术从传统的热解吸模式到溶剂脱附模式的扩展性思考。通过提取3种促燃剂(汽油,煤油和柴油)检材的效能比较与分析,优化了实验条件,确定了SPME的提取和溶剂脱附的方法,实验研究表明,SPME-溶剂脱附法是火场促燃剂残留物分析的有效方法之一。     

离线超临界流体萃取和气相色谱／质谱联用对实验室内空气中气相有机？…

通过固体吸附富集，再用超临界ＣＯ２脱附后用气相色谱及质谱技术对实验室内空气中气相有机污染物进行了考察，文中对采样和萃取条件进行了优化，并与热脱附所得结果做了比较，结果表明在２２ＭＰａ，８０℃时，用甲醇改性的超临界ＣＯ２进行萃取的结果优于热脱附法，该法鉴定出气相有机污染物中５２个组分，占色谱峰总面积的９９．６％。     

极性搅拌棒吸附萃取-热脱附-气相色谱/质谱法测定主流烟气捕集液中4种酚类物质

建立了极性搅拌棒吸附萃取-热脱附-气相色谱/质谱(GC/MS)法测定主流烟气捕集液中苯酚、邻甲酚、间甲酚、对甲酚4种酚类物质的分析方法。利用人工唾液收集主流烟气制备待测样品,样品用极性搅拌棒在室温下以900r/min吸附萃取60min;热脱附温度220℃,热脱附时间3min,冷阱温度-50℃进行热脱附后,通过GC/MS法进行分离检测。上述4种酚类物质在5~200μg/L范围内响应峰面积与其浓度呈良好的线性关系(r0.99),检出限在0.8~3.6μg/L之间,3个添加浓度(10、50、100μg/L)水平的平均回收率在82.8%~112.6%之间,相对标准偏差(RSD,n=5)为4.6%~12.2%。该方法操作简便,溶剂消耗少,灵敏度高,适用于烟气捕集液中苯酚、邻甲酚、间甲酚和对甲酚的分析检测。     

烃类在ZSM-5分子筛上吸附的研究

本文对烃类在不同ZSM-5分子筛上吸—脱附的动态行为进行了研究。描述了程序升温脱附过程中扩散系数和扩散活化能的计算模型;测定了环己烷在ZSM-5分子筛样品上的迎头流出曲线。发现环己烷在ZSM-5分子筛上的吸附存在着可逆和不可逆两个过程,后者受环己烷在分子筛内部孔道的扩散所制约,同时不同样品上吸附性能的差异与X-射线衍射峰的特征以及甲醇转化为汽油的反应性能之间存在着密切关系。谱图属A 型的ZSM-5分子筛对环己烷有较大的吸附量、较小的孔道扩散障碍和较好的甲醇转化反应稳定性。     

制备溶剂对NiCoB非晶态合金催化剂结构及糠醛加氢性能的影响

采用化学还原法在不同单一和复配溶剂体系中制备了一系列NiCoB非晶态合金催化剂,对其液相糠醛加氢性能进行了考察,并采用N_2吸附-脱附等温线、ICP、FE-SEM、HRTEM、XRD、XPS等手段进行了表征。结果表明,在相同反应条件下,制备溶剂的表面张力、黏度、极性大小和溶解度常数等对NiCoB非晶态合金催化剂的组成、形貌和结构及其糠醛加氢反应性能均产生重要影响。由甲醇/乙二醇复配溶剂(MEG,体积比1∶1)制备的NiCoB-MEG催化剂具有最理想的糠醛液相加氢制糠醇性能,糠醛转化率达到96.4%,糠醇选择性达到83.49%,这可归因于甲醇和乙二醇之间的协同作用促进了金属组分的分散和还原。     

喷气燃料中胶质化合物的质谱分析

喷气燃料中的不安定组分对燃料安定性影响很大,不安定组分主要集中在胶质化合物中,胶质化合物的存在会增加燃烧积炭,影响航空发动机的正常使用[1-2]。不安定组分含量极少,必须通过一定条件的分离和富集才能进行分析和评价。本文采用中性氧化铝吸附和极性溶剂脱附的方法分离制备     

Dispersive liquid-liquid microextraction of organophosphorous pesticides using nonhalogenated solvents

Dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography and mass spectrometry (GC-MS) was applied to the determination of five organophosphorous pesticides (OPPs) in water samples. The analytes included in this study were prophos, diazinon, chlorpyrifos methyl, fenchlorphos, and chlorpyrifos. The use of nonhalogenated solvents (cyclohexane, heptane, and octane) as extraction solvents was investigated using acetone, acetonitrile, or methanol, as dispersion solvents. The combination of less polar dispersion solvents (1-propanol and 2-propanol) and nonhalogenated extraction solvents was also studied in dispersive liquid-liquid microextraction for the first time. Several experimental conditions were tested (nature and volume of extraction solvents, nature and volume of dispersion solvents, salting-out effect) and the corresponding enrichment factors and recoveries were evaluated. The best microextraction condition was obtained using 50 μL of cyclohexane and 0.3 mL of 1-propanol. The detection and quantification limits were in the low ppt range, with values between 3.3-8.0 ng/L and 11.0-26.6 ng/L, respectively. Relative standard deviations were between 6.6 and 13.1% for a fortification level of 500 ng/L. At the same fortification level, the relative recoveries (RR) of Alvito's dam water, Judeu's river water, and well water samples were in the range of 50.3-97.1%.     

Studies on the extraction behaviour of plutonium(IV) from mixed aqueous-organic media with sulphoxides

Extraction behaviour of plutonium (IV) from nitric acid media by two long-chain aliphatic sulphoxides, namely, di-n-hexylsulphoxide and di-n-octylsulphoxide has been investigated in the presence of several water-miscible organic solvents to study their possible synergistic effect on metal ion extraction. Methanol, ethanol, n-and iso-propanol, dioxane, acetone as well as as acetonitrile were used as the organic component of the mixed (polar) phase. These additives affected the extraction to varying degrees. Thus, extractability of Pu increases 2–3 fold with increasing concentration (upto 20%) of acetonitrile, acetone, methanol and ethanol while it decreases with increasing concentration of n-and isopropanol. At high concentration of the former, synergism changes into antagonism. Possible reasons for such behaviour are briefly discussed. Among these organic additives, maximum enhancement in the extraction of Pu(IV) was observed in the presence of acetonitrile. The relative increase in extraction was found to be more at lower sulphoxide concentrations.     

菠菜叶绿素的浸提和协同萃取反应

有机溶剂;菠菜叶绿素的浸提和协同萃取反应     

Determination of anionic surfactants in lubrication fluids

A simple method is described for the isolation and determination of anionic surfactants in oils and emulsions used as lubricants in metal working processes. The oils were separated on silica gel solid phase extraction columsn by successive elution of solvents with increasing polarity as hexane, diisopropyl ether, acetic acid ethyl ester, acetone and methanol/NH₃ (8:1). The most polar methanol phase, which contains the surfactants, was titrated with Hyamine and the end point was determined potentiometrically using an ion sensitive electrode. The retention behaviour of sulfonates and sulfates on the sorbent has not been affected by other lubricants.     

Solvent effects on structural properties of SiO2 gel using n-octylamine as a catalyst

We have investigated the effect of solvent(ethanol, acetone, isopropanol) on the sol–gel process of tetraethylorthosilicate (TEOS) in which case, n-octylamine is used as polycondensation catalyst. Two sets of materials were prepared in the laboratory by using ethanol, acetone and isopropanol as solvents respectively: (1) xerogels from TEOS/n-octylamine, and (2) composites from TEOS/polyhedral oligomeric silsesquioxanes /n-octylamine. The chemical structure of xerogels was studied by FTIR, TG–DSC, scanning electronic microscope and nitrogen adsorption–desorption isotherms techniques. The results have shown that the solvents directly influence the gel time. Gel time is longer for acetone than that of ethanol and isopropanol. In the case of TEOS xerogels, the materials are essentially mesoporous when n-octylamine is used as a catalyst. Silica, when ethanol is used as a solvent, exhibits a more narrow pore size showing textures with a microstructure uniformly distributed with different porosity levels. However, when the aged-isopropanol gel is used, silica shows textures with a microstructure nonuniformly distributed.     

Combination of hollow‐fiber‐supported liquid membrane and dispersive liquid–liquid microextraction as a fast and sensitive technique for the extraction of pesticides from grape juice followed by high‐performance liquid chromatography

The simultaneous use of a hollow‐fiber‐supported liquid membrane and dispersive liquid–liquid microextraction for the determination of pesticides directly in grape juice was investigated. The detection and quantification were performed by liquid chromatography with diode array detection. The optimum extraction condition was reached by filling the pores of the membrane wall with dodecanol and using hexane/acetone as extraction/dispersion solvents. Salt addition had a highly negative effect on the extraction efficiency and the optimum extraction time was 60 min. The volume of hexane/acetone mixture and the sample pH did not affect the signal at the levels studied. Therefore, an intermediate amount of these solvents (250 μL; 1:7.5 v/v) and pH 6 were selected. The optimum desorption condition was obtained with acetonitrile and 10 min of desorption time. The linear working range varied from 58 to 500 μg/L (parathion‐methyl), 62–500 μg/L (difenoconazole) and 107–500 μg/L (chlorpyrifos), with correlation coefficients ranging from 0.9980–0.9942. The limits of detection and quantification found were, respectively, 17 and 58 μg/L for parathion‐methyl, 19 and 62 μg/L for difenoconazole and 32 and 107 μg/L for chlorpyrifos. The relative standard deviation ranged between 3.5 and 11.2%.     

Calibration of chromatographic systems for quantitative prediction of chromatography of homopolymers

A method is proposed for obtaining from the experimental data the main parameters, which determine the chromatographic behavior of homopolymers: a dependence of the adsorption interaction parameter on the mobile phase composition, and the pore volume and pore size values. The interaction parameter can be determined by this method in both adsorption, critical, and SEC-type regimes of chromatography. The method is tested in ‘mathematical experiments’ with theoretical data that mimic experiments, and is applied to calibrate real chromatographic systems. With the obtained calibrations quantitative modeling of chromatograms of PEG samples on two typical ODS columns with different pore size in methanol/water and acetone/water mixed solvents is performed; the simulation results are compared with real chromatograms.     

Volatile organic solvent-induced signal enhancements in inductively coupled plasma-mass spectrometry: a case study of methanol and acetone

Methanol and acetone were used to study effects of organic matrix on signal intensities of elements from ⁷Li to ²³⁸U and oxide yields in inductively coupled plasma-mass spectrometry (ICP-MS). Enhancement or suppression of analyte signals in the presence of methanol or acetone depends on the volatility and concentration of the compound and mass and ionization potential of elements concerned as well as ICP-MS operating conditions. Presence of a low concentration of methanol or acetone enhances the intensities of elements in order of decreasing mass. This is attributed to the spatial shift of the zone of maximum ion density, which, in turn, affects the extraction of ions from the plasma to the sampling cone. The possible effect of liquid methanol or acetone on nebulization and/or transport efficiency was avoided by using carry-over effect experiment. More volatile acetone more readily suppresses signals of all the elements under investigation. A higher concentration of methanol also suppresses intensities of the elements due to resultant cooling of the plasma. The enhancement effect of methanol and acetone appears to be more related to the amount of carbon present in the plasma than the difference between the functional groups of organic solvents. The oxide yield decreases in the presence of methanol, the magnitude of which depends on the nebulizer gas flow rate used. However, the reduced oxide yield is insufficient to account for the signal enhancement. Our results for ⁷⁵As and ⁷⁸Se agree with the C⁺-species–analyte atom charge transfer reaction hypothesis.     

Adsorption and desorption properties of trans-resveratrol on cellulose cotton.

The adsorption and desorption properties of trans-Resveratrol (Res) on the cellulose cotton were investigated under various conditions, such as the pH, alcohol percentage, temperature and equilibrium times. Moreover, the acidic-dissociation constants were determined to be pKa1 = 8.01, pKa2 = 9.86 and pKa3 = 10.5 by a curve-fitting method. Also, it was found that the adsorption depended on the temperature and salting effect. On the other hand, the desorptions from cellulose were examined using several kinds of water-miscible organic solvents (methanol, ethanol, acetone and THF).