Temperature Programming for High-Speed GC

Fast temperature programming (20-50 °C/min) is used with relatively short separation columns to achieve high-speed separations of mixtures covering a wide boiling point range. A cryofocusing inlet is used to obtain narrow injection plugs. High-speed temperature-programmed chromatograms are evaluated by considering local peak capacity as a function of carbon number and boiling point for the normal alkanes in the range C(8)-C(19). The peak capacity generation rate (peaks per second) as a function of carbon number and the total cumulative peak capacity as a function of time are also considered for various column lengths and carrier gas flow rates. Column lengths in the range 3.6-25.4 m and average carrier gas velocity values in the range 50-200 cm/s are considered. For a 6.8-m-long, 0.25-mm-i.d. column operated at an average carrier gas velocity of about 100 cm/s and using a nominal programming rate of 50 °C/min, C(19) elutes in 178 s with a total peak capacity of 168 peaks. If the programming rate is reduced to 20 °C/min, the C(19) elution time more than doubles but the total peak capacity increases by only 20%. For a 25.4-m-long column using a nominal 50 °C/min programming rate, the C(19) retention time is 262 s with a peak capacity of 279 peaks. The use of average carrier gas flow rates greater than about 100 cm/s, which is common in isothermal high-speed GC, results in a considerable loss in total peak capacity with remarkably little reduction in analysis time.     

Simultaneous Temperature and Holdup Time Ratio Optimization for Tandem Column Tunable Selectivity with High-Speed GC

Analysis time for high-speed, capillary column GC is reduced by the use of a pressure-tunable tandem combination of a nonpolar poly(methylsiloxane) (DB-5) column and a polar trifluoropropyl poly(methylsiloxane) (Rtx-200) column operated isothermally at an optimized oven temperature. By adjusting the pressure at the midpoint between the two columns, the residence times of all sample components are adjusted to give the maximum resolution of the critical component pair. The result is a two-dimensional optimization where the column temperature and the midpoint pressure were adjusted to give the shortest possible analysis time. A previously defined relative resolution function, which requires only empirical capacity factor data for the target compounds, is used as the dependent variable in the optimization algorithm. The resulting three-dimensional resolution map is projected parallel to the relative resolution axis in order to obtain a useful two-dimensional display from which the optimal operating conditions can be determined.     

吹扫捕集-气相色谱法测定水中挥发性有机物

本文采用吹扫捕集进样,DB-624毛细管柱分离,FID检测器,外标法定量测定水中部分挥发性有机物,利用标准物质得到相应检出限,相对标准偏差,加标回收率。探讨实验中的一些问题并提出建议。     

对三唑磷气相色谱检测中采用石英毛细柱为分析柱的研究

本文以三唑磷农药为例,实验了石英毛细管色谱柱在农药分析中的应用,为农药分析方法的开发和研究提供新的指导。本文建立三唑磷农药的石英毛细管色谱柱分析方法,该方法以FID为检测器,邻苯二甲酸二环已酯为内标,检测三唑磷的平均加收率为101.67%;标准偏差为0.1788;变异系数为0.89%;线性相关系数为0.9999,该检测方法结果稳定、可靠、可行性好。     

Epitaxial Growth of Oriented Metalloporphyrin Network Thin Film for Improved Selectivity of Volatile Organic Compounds

This study reports an oriented and homogenous cobalt‐metalloporphyrin network (PIZA‐1) thin film prepared by liquid phase epitaxial (LPE) method. The thickness of the obtained thin films can be well controlled, and their photocurrent properties can also be tuned by LPE cycles or the introduction of conductive guest molecules (tetracyanoquinodimethane and C₆₀) into the PIZA‐1 pores. The study of quartz crystal microbalance adsorption confirms that the PIZA‐1 thin film with [110]‐orientation presents much higher selectivity of benzene over toluene and p‐xylene than that of the PIZA‐1 powder with mixed orientations. These results reveal that the selective adsorption of volatile organic compounds highly depends on the growth orientations of porphyrin‐based metal‐organic framework thin films. Furthermore, the work will provide a new perspective for developing important semiconductive sensing materials with improved selectivity of guest compounds.     

A Comparison of Cryofocusing Injectors for Gas Sampling and Analysis in Fast GC

The performance of two cryofocusing injectors for fast gas chromatography has been studied. The first system traps analytes onto bare metal tubes and rapidly vaporizes them upon ballistically heating the tube using a capacitance discharge. The second is a microloop injector in which analytes are cryotrapped onto short lengths of narrow-bore fused silica tubing with various coatings. The ballistically heated injector is capable of sampling and injecting compounds from air faster than the microloop system, because the metal tube can be heated and cooled more rapidly. Both systems are capable of cryotrapping compounds as volatile as butane at -90 °C, and the microloop system can trap ethane when a section of a porous layer open-tubular (PLOT) column is used as the sample loop. In addition, the microloop injector can be used without cryointegration to analyze compounds regardless of their volatility, as long as they are present in the samples at detectable concentrations. Because the ballistically heated injector is flushed prior to injection, it can introduce only compounds that are adsorbed onto its metal trap. Comparison of chromatograms obtained using the two injectors show similar chromatographic resolution. Both traps are susceptible to freezing during the cryotrapping step, but the use of an inline Nafion dryer allows air saturated with water vapor to be sampled using both systems for 3 min without plugging the trap. Thermal decomposition during the injection step can occur for labile species in the ballistically heated trap, but even the highly unstable compound ethyl diazoacetate may be injected without breakdown in the microloop system.     

天然燃香燃烧产物中挥发性有机物分析研究

以天然原料制作而成的5种天然燃香,燃烧后利用热脱附-气相色谱质谱联用仪测定其燃烧产物中挥发性有机物TVOC的含量。结果表明,5种天然燃香燃烧后室内空气中TVOC安全通用技术条件》标准中的限值,于原料中加入炭粉在一定程度上可以降低天然燃香燃烧后空气中TVOC的含量。     

可加热塑料食品包装中 VOCs 分析

目的分析可加热塑料食品包装中的挥发性有机物(VOCs)。方法以甲醇为溶剂,配制异丙醇、乙酸乙酯、苯、乙酸丁酯、乙苯、间/对二甲苯、邻二甲苯、环己酮的标准溶液,利用顶空/气相色谱-质谱(HS/GC-MS)技术对7种可加热塑料食品包装进行了检测分析,对比加热前后塑料食品包装中VOCs的变化。结果原味酸牛奶包装袋在加热后环己酮的含量明显增加,小酥肉塑料包装盒在加热后异丙醇的含量增加比较明显,粽子塑料包装袋、玉米塑料包装袋、奶茶塑杯、自加热饭盒、微波饭盒在加热前后VOCs含量变化不大。结论这7种包装中的苯类溶剂残留量均超标。     

Database of Thermodynamic Properties for Aqueous Organic Compounds

Results are presented from a project undertaken to develop a database for properties of organic compounds relevant for geochemistry and environmental chemistry. The database includes critically assessed standard thermodynamic properties in aqueous solution, properties of pure compounds at ambient conditions, and bibliographic references. All information stored in the databases is accessible through a web interface, which includes calculation modules for evaluating properties at elevated temperatures and pressures. The basic structure of the databases and the web interface design are described.     

Carbon Isotope Analyses of Semivolatile Organic Compounds in Aqueous Media Using Solid-Phase Microextraction and Isotope Ratio Monitoring GC/MS

Solid-phase microextraction (SPME) was used to facilitate the measurement of stable carbon isotope compositions (at natural abundance) of six organic compounds representing four compound classes in aqueous solution. Toluene, methylcyclohexane, hexanol, and acetic, propionic, and valeric acids were extracted from aqueous solutions with appropriate SPME phases and thermally desorbed into the split/splitless inlet of an isotope ratio monitoring gas chromatograph/mass spectrometer (irmGC/MS). Hydrophobic compounds (toluene, methylcyclohexane, hexanol) extracted by a nonpolar SPME phase were slightly (≤0.5‰) enriched in (13)C while organic acids extracted with a polar phase were depleted in (13)C to a somewhat greater degree (≤1.5‰) relative to material remaining in the aqueous phase. Isotopic fractionation was not observed to vary systematically as a function of equilibration time or solute concentration. Further, isotope fractionation did not vary consistently with the partition coefficient (K(fw)). However, both salinity and cosolvent effects, which altered the partition coefficients of the solutes, also yielded a reduction in the magnitude of isotopic fractionation (to ≤0.4‰ for the hydrocarbons, ≤0.5‰ for the organic acids). We conclude that fractionations are most likely associated with the interactions of organic compounds with the organic phase coating SPME fibers and are specifically due to mass-dependent energy shifts upon solution of each analyte into the organic phase. In addition, fractionations are also influenced by energy shifts associated with electrostatic forces acting on the analyte in the water phase during the partitioning process. The magnitude of isotopic fractionations can be minimized under conditions appropriate for the analysis of natural waters, and with careful calibration, SPME and irmGC/MS should be a valuable means for isotopic analyses for a wide range of organic constituents in aqueous samples.     

Study of Selectivity of Extractants for Extraction of Organosulfur Compounds from Model Solutions

Inorganic Materials - Extraction of sulfur compounds from oil and petroleum products is a high priority task associated with tightening of the criteria of fuel quality control, negative impact of...     

超导化合物临界温度Tc的经验公式

本文采用广义的 Pines 凝胶模型导出电子—声子耦合系数 g 的解析表达式,并在 Gennes 方程组的基础上得到化合物德拜温度 T_d 的计算公式。最后把求得 g 和 T_d 代入修正的 BCS 公式中,算出超导化合物的临界温度。计算表明:对于超导多元化合物 La_(1.85)Ba_(0.15)CuO_4、(RE)_(?)Ba_2Cu_3O_(?)和 Tl_(?)Ba_(1.7)Ca_(1.3)Cu_(?)O_(?)而言,临界温度计算值与实验值的最大相对误差小于10%。     

色谱仪柱温测试系统的设计与开发

针对液相和气相色谱仪柱温箱温度检定的应用需求,从传感器和显示仪表的制作两方面考虑,确定设计方案,设计铂电阻传感器外形结构,使其适用于液相色谱仪和气相色谱仪柱温的检定;根据液相和气相色谱仪检定规程中对柱温检定项目的要求,编写单片机程序,通过单片机的控制实现检定项目的选择与检定数据的自动记录和计算,给出检定结果。     

New Conditions for Intercalation of Organic Compounds into Semiconductor Nanomaterial

The intercalation of organic guests,2-methyl pyridine(2-picoline) and 3-methyl pyridine(3-picoline) into semiconductor layered nanomaterial(MnPS3) was investigated.New conditions were applied.New phases appeared and lattice expansions were 0.36 nm for 2-picoline intercalation and 0.728 nm for 3-picoline intercalation.The XRD(X-ray diffraction) patterns exhibit sharp hkl reflections confirming that the material is highly crystalline.The interlayer gap(0.64 nm) of the host plays a role for the arrangement of ...     

HPLC无孔径载体柱用于快速分离蛋白质和多肽

介绍了一种新型的高效液相色谱柱的结构特点及其在蛋白质、多肽及遗传工程产品分析中的应用。在相同的洗脱条件下，与常规柱相比，无孔径载体柱高效、快速，特别是它能分离分子量较大和疏水性较强的蛋白质。此外，就无孔径载体柱在使用过程中对仪器的要求作了阐述，还讨论了温度对柱效的影响以及灵敏度与梯度时间的关系等。     

卷烟商标残留成份SPME-GC/MS分析

本文建立了一种研究卷烟商标残留挥发性有机物(VOCs)的快速分析方法。利用顶空固相微萃取(HS-SPME)技术对样品进行前处理,与GC-MS联用对卷烟商标残留有机挥发性成份进行分析。并对纤维头类型、平衡时间、萃取温度等参数进行了优化,着重对SMPE重复性进行了讨论。确定SPME条件为65μmCW/DVB纤维头、平衡时间为20min、萃取温度为100℃。结果表明该方法可有效地分析羟基环已基苯甲酮、二苯甲酮、酯类化合物以及苯系物,为卷烟商标质量控制与有害成份监控提供依据。     

肉桂油气相色谱与气质联用分析

目的:建立肉桂油中桂皮醛的含量测定方法和鉴定挥发性化学成分。方法:气相色潜法,3mm×4m不锈钢柱,10％PEG-20M为固定液,Chromosorb WAW 60-80目担体,FID检测器,柱温190℃;气质联用,以HP-5毛细管柱,柱温起始120℃保持5min后以5C/min升温至150(保持7min,检测质荷比范围10-425。结果:桂皮醛在2-10mg/mL范围内具良好线性关系,平均回收率为99.98％,RSD为1.3％,气质联用鉴定了39种化合物。结论:方法简便,快速,准确,可有效排除其它成分的干扰。     

空气中挥发性有机物的热脱附—气相色谱分析

空气污染严重影响人们的身体健康,引起环保检测部门的高度重视,而空气挥发性有机物含量是空气污染的重要指标之一,因此,测定该参数对于空气质量评价非常重要。本文建立的热脱附-气相色谱联用分析方法,为空气挥发性有机物提供一种灵敏度高、操作简便、重现性好、准确可靠的新方法。     

高速主轴滚子轴承的动特性分析

针对高速主轴滚子轴承工况特点建立油气润滑下的滚子轴承拟静力学模型,通过具体算例分析了转速、载荷等工况条件以及轴承游隙和空心滚子等因素对滚子轴承的动态性能的影响,并在此基础上结合Lundberg寿命理论计算相关参数对滚子轴承疲劳寿命的影响。结果表明:高速轻载工况下轴承打滑比较严重,通过施加适量的预载荷或者使用空心滚子可以减小轴承的打滑,然而过大的预载荷会导致轴承疲劳寿命迅速降低;高速下空心滚子可以减轻滚子轴承打滑程度并提高轴承疲劳寿命。