毛细管气相色谱法测定丙烯中烃类杂质的含量

以PLOT／Al2O3石英毛细管柱为分析柱,采用氢火焰离子化检测器,建立了测定丙烯中烃类杂质含量的毛细管气相色谱法。丙烯中烃类杂质含量测定结果的相对标准偏差小于5％,分析时间约30min,测定值与国家标准方法基本一致。该方法操作简便,分析速度快,准确度高,重复性好。     

毛细管气相色谱法测定小麦粉中的过氧化苯甲酰

在国标GB／T18415—2001的基础上,以OV-1701石英毛细管柱为分析柱、氢火焰离子化检测器为检测器,采用气相色谱法测定小麦粉中的过氧化苯甲酰。小麦粉中过氧化苯甲酰测量结果的相对标准偏差小于1.1％,加标回收率为96．5％～101．0％,检出限为10μg／mL,样品分析时间约为20min。与国标方法相比,该法不仅缩短了检测时间,而且提高了检测灵敏度。     

一种直热式快速气相色谱快速升温装置的设计

用大电流脉冲直接加热不锈钢毛细管柱, 将脉冲间隔调整到正好使柱管局部完成热平衡, 用快速PID技术控制脉冲频率和宽度, 设计了一种直热式快速升温装置. 该装置最高升温速率可达到5 ℃/s, 升温范围 40~150 ℃, 程序升温线性相关系数大于0.9996, 最大功耗74 W, 加热平均功耗小于50 W, 在34 s内完成nC8~nC17 10种正构烷烃的分离, 保留时间重复精度误差RSD在0.22%~0.55％之间, 降温和平衡时间仅为30 s. 与常规气相色谱仪相比, 该装置分析挥发性和半挥发性有机物速度可提高20倍以上, 专用于快速气相色谱仪.     

季戊四醇和双季戊四醇气相色谱分析方法研究

应用柱前衍生-气相色谱法分离并测定了反应混合物中同存的季戊四醇(MPE)和双季戊四醇(DPE)、衍生化反应系在120℃加热的封闭试管中进行。将含有MPE及DPE的试样与甘露醇,4-二乙氨基吡啶及乙酸酐和吡啶的混合溶液置于此试管中,密封,加热并每隔10 min摇动溶液一次直至溶液成澄清液。此时MPE,DPE及甘露醇均生成乙酸酯衍生物,取此澄清溶液0.2 mL进行色谱分析,分离及测定时采用内装3%OV-17+3%XE-60及过180~150μm 101AW-WS的不锈钢管(1 m×3 mm)作色谱柱。应用此方法分析了不同含量的4个试样,所得结果的RSD值,测MPE时小于0.21%,测DPE时小于0.14%。测定值与标准值之间的偏差均小于0.7%。     

气相色谱对映体标记法测定实际样品中氨基酸

]本文在自制的手性（OV-225-L-缬氨酰-叔丁胺）交联毛细管柱上,用对映体标记法测定了豆浆水、海参水解液、裸腹蚤鲫鱼血、鲫鱼蛋白和轮虫等实际样品中的氦基酸含量,取得了较好的结果,其中,用对映体标记的氨基酸含量测定相对偏差小于5％。     

串联毛细管柱对甲基叔丁基醚产品及其杂质的色谱分析

采用非极性的OV-1柱及极性的FFAP柱串联而成的毛细管柱分析甲基叔丁基醚(MTBE)产品的全组成,该法能完全分离MTBE及其杂质组分,相对标准偏差小于3．5％。具有分离效果好、结果准确、操作简单等优点。     

指数程序薄涂柱气相色谱法测定甲胺磷

甲胺磷是一种兼具杀虫、肥料两种性能的高效、广谱农药,由于甲胺磷加热到一定温度时分解(185～190℃),所以其色谱分析时操作温度不能太高,用气相色谱法测定甲胺磷已有报道,但用指数程序薄涂柱气相色谱法测定尚未见报道,该法选择了DEGS为固定液,将0.34％、0.49％、0.7％的DEGS涂在80～100目硅烷化玻璃微球载体上,填入1 m不锈钢色谱柱进行测定,当柱温为150℃时甲胺磷即与其它成分分离,出峰时间仅为2.25 min,且峰形对称,这样既避免了操作温度高易使甲胺磷分解的缺陷,又提高了定量的准确性和分析速度,该法应用于多种样品中甲胺磷的测定,结果令人满意。     

高效液相色谱检测Zn（Ⅱ）、Cd（Ⅱ）、Co（Ⅱ）、Pb（Ⅱ）、Ni（Ⅱ）、Cu（Ⅱ）、Hg（Ⅱ）

用双-(2-羟乙基)二硫代甲酸铵(HEDC)在反相液相色谱中作检测某些金属离子的衍生化试剂，HEDC的金属螯合物微溶于水，可直接水样注射于C18柱中进行检测，范围为0．006～10mg／L相对偏差1％～2％，检测波长254nm，金属汞的整合物在HPLC分析前进行浓缩富集检测限可低至0．06～25μg／L，相对偏差小于2％。     

阴离子洗涤剂选择性电极电位滴定法测定石油磺酸钠

本文以阴离子洗涤剂选择性电极作指示电极,用电位滴定法测定石油磺酸钠的浓度。当浓度在20％左右时,相对偏差小于±1％,测定选矿尾水中痕量石油磺酸钠的相对偏差为±8.1％。本法操作简单,适宜于快速分析。     

氟钽酸钾中氟的除去和微量碳的测定

本提出铝片－硼酸－磷酸十硼酸饱和液的新除氟体系。系统地研究了铝片的用量，燃烧温度，燃烧时间和氧气流速对除氟和二氧化碳析出的影响。用燃烧－气相色谱法测定了氟钽酸钾中微量，方法的检测限为５μｇ／ｇ，相对偏差为±１０％，已应用于有关工厂的日常分析。     

原位合成分子筛多孔层毛细管柱的制备与性能考察

在毛细管内壁,原位合成了Ｎａ－Ａ型分子筛,成功制备出一类新型分子筛多孔尾毛细管柱。和涂渍相比,原位合成法在毛细管内壁形成的分子筛层更加均匀、致密度、更能体现出分子筛对低碳烃的分离特性,实验表明用超短毛细管柱即可对低碳烃进行良好的分离。     

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。     

Performance characteristics of a new prototype for a portable GC using ambient air as carrier gas for on-site analysis

The performance characteristics of a portable GC instrument requiring no compressed gas supplies and using relatively lightweight transportable components for the analysis of volatile organic components in large-volume air samples are described. To avoid the need for compressed gas tanks, ambient air is used as the carrier gas, and a vacuum pump is used to pull the carrier gas and injected samples through the wall-coated capillary column and a photoionization detector (PID). At-column heating is used eliminating the need for a conventional oven. The fused silica column is wrapped with heater wire and sensor wire so that heating is provided directly at the column. A PID is used since it requires no external gas supplies and has high sensitivity for many compounds of interest in environmental air monitoring. In order to achieve detection limits in the ppb range, an online multibed preconcentrator containing beds of graphitized carbons and carbon molecular sieves is used. After sample collection, the flow direction through the preconcentrator is reversed, and the sample is thermally desorbed directly into the column. Decomposition of sensitive compounds during desorption is greater with air as the carrier gas than with hydrogen.     

Fast Capillary Gas Chromatography: Comparison of Different Approaches

Savings in analysis time in capillary GC have always been an important issue for chromatographers since the introduction of capillary columns by Golay in 1958. In laboratories where gas chromatographic techniques are routinely applied as an analytical technique, every reduction of analysis time, without significant loss of resolution, can be translated into a higher sample throughput and hence reduce the laboratory operating costs. In this contribution, three different approaches for obtaining fast GC separations are investigated. First, a narrow-bore column is used under conventional GC operating conditions. Secondly, the same narrow-bore column is used under typical fast GC conditions. Here, a high oven temperature programming rate is used. The third approach uses a recent new development in GC instrumentation: Flash-2D-GC. Here the column is placed inside a metal tube, which is resistively heated. With this system, a temperature programming rate of 100°/s is possible. The results obtained with each of these three approaches are compared with results obtained on a column with conventional dimensions. This comparison takes retention times as well as plate numbers and resolution into consideration.     

Sensitive determination of styrene and related compounds in human body fluids by headspace capillary gas chromatography with cryogenic oven trapping

Summary A simple and sensitive method is presented for determination of styrene, toluene, ethylbenzene, isopropylbenzene andn-propylbenzene in human body fluids by capillary gas chromatography (GC) with cryogenic oven trapping. After heating a blood or urine sample containing each compound andp-diethylbenzene (internal standard, IS) in a 7.0-mL vial at 60°C for 20 min, 5 mL of headspace vapor was drawn into a glass syringe and injected into a GC. All vapor was introduced into an Rtx-Volatile middle bore capillary column in splitless mode at oven temperature of 20°C to trap entire analytes, and the oven temperature then programmed to 280°C for GC measurements by flame ionization detection. The present conditions gave sharp peaks of each compound and IS, and low background noises for whole blood or urine samples.     

密闭舱内VOCs现场快速定量检测技术与装置研究

该文发展了可对压强变化的密封舱实现计量采样-富集的采样技术,基于薄壳金属筒式低功耗均温色谱柱组件,结合微池热导检测器/小型氢火焰离子化检测器,建立了一种对密闭舱内挥发性有机物(VOCs)进行现场快速定量检测的方法和装置。根据负压罐和密封舱的压强差值和绝压值以及温度,计算出有效采样体积(折算到标准大气压),进而计算出富集倍数。当有效采样体积为100 mL时,对甲苯的富集倍数大于400倍。所研制的色谱柱组件将色谱柱紧密排绕在薄壳式金属筒外层,加热丝紧密排绕在金属筒内侧,可实现小于0.4℃的均温效果和40℃/min的程序升温速率。在以10℃/min加热至300℃过程中,功耗低于35 W,300℃恒温加热功率仅需28 W。将色谱柱组件的分离性能(包括半峰宽、柱效、分离度和重复性)与实验室进口色谱仪炉箱得到的结果进行对比,发现两种加热方式得到的色谱分离性能相当。采用多种VOCs样品对采样-富集性能进行评价。在高速分离模式下,5 min内可实现53种VOCs的快速分离,半峰宽均小于0.8 s。研制出的整机已应用于烃类、苯系物、醇类、醛酮类等多种VOCs的快速分析,并与商品化便携式气相色谱或气相色谱-质谱的性能参数进行了对比,结果满意。     

Development of a Dual Capillary Column GC Method for the Trace Determination of C2–C9 Hydrocarbons in Ambient Air

An analytical method based on a dual capillary gas chromatographic technique combining the advantages of GasPro PLOT and a non polar narrow bore WCOT column was developed for the analysis of air samples containing C2–C9 NMHCs. A refocusing step was not required due to the fast heating rate of the sample preconcentration trap and the resolving power of the PLOT column for C2 and C3 NMHCs. Water had to be removed from the air samples to avoid plugging of the columns if the initial GC oven temperature was below ambient temperature. To dry air samples, a scrubber and a cryogenic technique were employed. The interferences caused by carbon dioxide were reduced by purging the loaded sample preconcentration trap with helium. The dual column system was compared to a method employing a refocusing device and a single narrow bore WCOT column. Both systems provided a high degree of precision. However, the dual column approach was superior to the single column system due to better resolution of low molecular weight components.     

Joule heating induced transient temperature field and its effects on electroosmosis in a microcapillary packed with microspheres

The Joule heating induced transient temperature field and its effect on the electroosmotic flow in a capillary packed with microspheres is analyzed numerically using the control-volume-based finite difference method. The model incorporates the coupled momentum equation for the electroosmotic velocity, the energy equations for the Joule heating induced temperature distributions in both the packed column and the capillary wall, and the mass and electric current continuity equations. The temperature-dependent physical properties of the electrolyte solution are taken into consideration. The characteristics of the Joule heating induced transient development of temperature and electroosmotic flow fields are studied. Specifically, the simulation shows that the presence of Joule heating causes a noticeable axial temperature gradient in the thermal entrance region and elevates a significant temperature increment inside the microcapillary. The temperature changes in turn greatly affect the electroosmotic velocity by means of the temperature-dependent fluid viscosity, dielectric constant, and local electric field strength. Furthermore, the model predicts an induced pressure gradient to counterbalance the axial variation of the electroosmotic velocity so as to maintain the fluid mass continuity. In addition, under specific conditions, the present model is validated by comparing with the existing analytical model and experimental data from the literature.     

Gas chromatography with ballistic heating and ultrafast cooling of column

An overview of the existing methods for minimization of the analysis time in gas chromatography (GC) is presented and a new system for fast temperature programming and very fast cooling down is evaluated. In this study, a system of coaxial tubes, a heating/cooling module (HC-M), was developed and studied with a capillary column placed inside the HC-M. The module itself was heated by a GC oven and cooled down by an external cooling medium. The HC-M was heated at rates of up to 330 °C min⁻¹ and cooled at the rate of 6000 °C min⁻¹. The GC system was prepared for the next run within a few seconds. The HC-M permits good separation reproducibility, comparable with that of a conventional GC, expressed in terms of relative retention times and peak areas of analytes reproducibilities. The HC-M can be used within any commercial gas chromatograph.     

Optimizing capillary column backflush to improve cycle time and reduce column contamination

Interest in decreasing cycle times in capillary GC analyses has driven much of the instrumental developments of the last decade. Recent developments in GC instrumentation now make it reasonable to consider backflushing capillary columns on a routine basis. Significant reduction in analysis and total cycle times (typically 15–50% depending on the application) are readily achieved for analyses that currently require an extended temperature program and bakeout period to remove retained sample components and column contaminants. Setup and optimization of backflush conditions are relatively straight forward as long as some basic concepts are well understood. The parameters affecting capillary column backflushing are described. Examples are shown that help visualize what happens during backflush. The relationship between oven ramp rate and flow turns out to be an important variable that dictates minimum backflush times in temperature programmed CGC. Backflush times corresponding to 2–5 void volumes in the reversed direction are usually sufficient for backflushing, if performed after each temperature programmed run.