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1.
The paper concerns the analysis of volatile hydrocarbons on newly designed and produced capillary columns. According to the type of coating used, the columns are of the PLOT type, and according to the adsorbate‐adsorbent type interactions they belong to the category of complexation GC. The adsorbent used was silica, whose surface was modified with bonded 2‐(3‐triethoxysilylpropylimino)‐3‐(benzyl)‐pentanone‐4 to change the adsorption characteristics. The presence of the ketoimine group of strongly electron‐accepting properties permitted the binding of transition metals. The metal ions are capable of interacting selectively with nucleophilic compounds including olefins. The transition metal ions used for sorbent modification were copper(II) chlorides and nickel(II) chlorides. The supported adsorbent was immobilised by bonding the modified silica to the column walls by a film of poly(dimethylsiloxane). Due to this strategy, the coating was very stable, no sorbent loss from the column was observed and the column could be washed with solvent. Besides exemplary separations, the paper quotes retention parameters of the group of compounds analysed and presents a discussion of the specific interactions between the adsorbate and adsorbent.  相似文献   

2.
基于吸附剂辅助电子制冷预浓缩技术,建立了多维切割双柱气相色谱-质谱/氢火焰离子化检测器(GC-MS/FID)同时测定环境空气中104种挥发性有机物(VOCs)的方法。将采集于苏玛罐中的环境空气样品在配有吸附剂的电子制冷预浓缩系统中富集、脱附、除水、除CO2和浓缩,然后通过GC-MS/FID的多维切割单元将C2~C3组分和C4~C12组分分别引入PLOT柱和InterCap-624柱进行分离。C2~C3组分用FID检测,以保留时间定性、外标法定量;C4~C12组分采用电子轰击离子源质谱检测,以保留时间和特征离子定性、内标法定量。考察了冷阱吸附剂种类、辅助压力控制单元压力设置、双柱切换时间切割点等参数对分析结果的影响,优化了GC-MS/FID条件,并评估了在此优化条件下的方法性能。104种VOCs在0.0446~0.892 μmol/m3范围内线性关系良好,相关系数(r)为0.9984~0.9999,对0.0446 μmol/m3和0.223 μmol/m3水平的混合标准气体重复6次进样,平均回收率为86.4%~116.1%,相对标准偏差为0.9%~11.3%;方法的检出限为0.145~1.90 μg/m3,定量限为0.435~5.70 μg/m3。该法稳定性好,灵敏度高,操作简便,可用于环境空气中104种VOCs的测定。  相似文献   

3.
A layer of elemental silicon has been deposited on the surface of stainless steel tubing by means of chemical vapor deposition (CVD). Two kinds of capillary column were prepared from the deactivated tubing: cross-linked, silanol-terminated polydime-thylsiloxane wall coated open tubular (WCOT) columns and molecular sieve 13X porous layer open tubular (PLOT) columns. Unlike fused silica capillary columns, stainless steel WCOT and PLOT columns can be operated at temperatures in excess of 400°C. High temperature simulated distillation has been performed successfully with a macro bore WCOT column and rapid PNA (paraffin, naphthene, and aromatic) analysis with a multidimensional gas solid chromatographic (GSC) system using PLOT columns.  相似文献   

4.
针对常规气相色谱填充柱分析稳定氢同位素的柱效低、峰宽大、保留时间长等问题,采用MnCl_2改性γ-Al_2O_3填充的石英毛细管柱开展了系统性柱效分析及氢同位素分析技术研究。研究结果表明,使用MnCl_2对γ-Al_2O_3进行改性后,可大大改善单纯的γ-Al_2O_3表面有序度、孔结构和吸附性质,并将正氢(o-H_2)和仲氢(p-H_2)峰洗脱在单一谱峰区域内。制备的长1.0 m、内径0.53 mm的石英毛细填充柱与热导检测器(TCD)级联测试,在体积浓度1至10 m L/L范围内有较好的线性关系,对于低浓度样品检测的相对误差不大于5%。H_2、HD和D_2的保留时间可分别缩短至39、46和60 s,检出限可分别降低至0.046、0.067和0.072 m L/L。毛细管填充柱较常规填充柱具有峰形尖锐、相邻组分分离度高、保留时间短、检出限低等优点,可用于低浓度氢同位素快速测量及氢同位素在线分析。  相似文献   

5.
A polymer phase, which was constructed with butyl methacrylate (BMA), an ionizable monomer (mono-(2-(methacryloyloxy)ethyl) succinate (MES)), and a crosslinking agent (ethylene dimethacrylate), was first formed in a porous-layered open-tubular (PLOT) capillary. The PLOT capillary was characterized with SEM and electrophoretic flow as the pH level, ionic strength and addition of organic modifiers in the running buffers changed. In addition, a bare capillary and a silica hydride based capillary (SiH-MES), which bore a monolayered MES phase on it, were used to compared with the BMA-MES capillary. Besides optimizing the capillary electrochromatographic (CEC) conditions for each group of analytes, which were a mixture of nucleosides and thymine, flavonoids, and phenolic acids,comparison of the separation selectivity among analytes between the BMA-MES and SiH-MES capillaries was done according to the velocity and retention factors obtained from the CEC data. Overall, the polymeric phase formed in the PLOT mode was capable of preventing blockage of the columns and was superior to the monolayered phase bonding with the same ionizable ligands for application in CEC as well as to the bare silica phase in CE.  相似文献   

6.
Generation of a large number of theoretical plates was attempted by capillary HPLC. Monolithic silica columns having small skeletons (ca. 2 μm) and large through-pores (ca. 8 μm) were prepared by a sol–gel method in a fused-silica capillary (50 μm I.D.), and derivatized to C18 phase by on-column reaction. High external porosity (>80%) and large through-pores resulted in high permeability (K=1.2×10−12 m2). The monolithic silica column in the capillary produced a plate height of about 12 μm in 80% acetonitrile at a linear velocity of 1 mm/s. Separation impedance, E value, was found to be as low as 200, that was about an order of magnitude lower than reported values for conventional columns packed with 5 μm particles. Reproducibility of preparation within ±15% was obtained for column efficiency and for pressure drop. It was possible to generate 100,000 plates by using a 130-cm column at very low pressure (<7 kg/cm2). A considerable decrease in column efficiency was observed at high linear velocity, and for solutes with large retention factors due to the slow mobile-phase mass transfer in the large through-pores. The monolithic silica columns, however, showed performance beyond the limit of conventional particle-packed columns in HPLC under favorable conditions.  相似文献   

7.
以甲基丙烯酸缩水甘油酯(GMA)和乙二醇二甲基丙烯酸酯(EDMA)为前驱体制备了新型聚合物多孔涂层毛细管开管(PLOT)柱固定相。通过优化聚合反应时间、致孔剂比例及交联剂比例获得了色谱性能良好的PLOT柱,扫描电镜结果显示毛细管柱内的多孔涂层厚度适中且均匀。在毛细管电色谱模式下,PLOT柱以反相色谱分离机理有效分离了中性、酸性和碱性小分子。人血清白蛋白(HSA)共价结合的蛋白亲和PLOT柱对5对手性对映体实现了较好的分离,且其分离度远高于HSA修饰的单层聚合物毛细管开管柱。PLOT柱分离烷基苯的日内、日间和柱间的相对标准偏差分别小于1.7%、4.8%和7.8%。  相似文献   

8.
Summary A new method is described to prepare polymeric porous-layer open-tubular (PLOT) columns by using a two-step in-situ polymerization technology. The integrated method involves a straightforward in-situ polymerization of the monomer. By using -(trimethoxysilyl)propyl methacrylate as a bridge, the porous polymer is bonded to the columns inner wall, and this polymer is crosslinked so the whole polymer looks like a single moleculer. The new column avoids the defects of traditional polymer PLOT columns where particles are easily released and swept through the column, causing blockage or a spiking detection signal. The new type of PLOT column is coated with a divinylbenzene and ethylene glycol dimethyl acrylate copolymer and has an increased polarity when compared to a conventional polymer Q-type PLOT column. The retention characteristics of the new column were evaluated and found to be comparable with the commercially available HP PLOT-U column. The inertness of the porous polymer allows the elution of a range of apolar and polar compounds: even most active and polar compounds such as H2O and H2S eluted symmetrically. The new column possesses high stability and can withstand temperatures up to 210 °C. With this new type of capillary columns, significantly better mechanical stability, temperature endurance, reproducibility, strong separation power and good inertness are obtained in combination with short analysis times.  相似文献   

9.
A gas chromatographic system was constructed to simultaneously measure ambient non-methane hydrocarbons (NMHCs) and halocarbons, which play significant roles in tropospheric ozone formation and stratospheric ozone loss, respectively. A heart-cut device based on a Deans switch was connected to two capillary columns to cover the full range of NMHCs and halocarbons. Analytes more volatile than C6 NMHCs and the halocarbon CFC-113 were separated with a PLOT column, while the remaining less volatile compounds were separated with a DB-1 column. Merge-and-split of the flows at the end of the two columns allowed the NMHCs and halocarbons to be observed simultaneously by electron capture detection (ECD) and flame ionization detection (FID). To avoid peak-overlap from the two columns while merging, programmed pressures were incorporated to control the Deans switch. In addition to the advantage of measuring two important classes of compounds in the atmosphere at the same time, this method has the additional benefit of using the homogeneity of atmospheric CFC-113 as an “intrinsic” internal reference. Thus, better data continuity, less consumption of gas standards, and real-time quality control can all be achieved.  相似文献   

10.
The capability of the helium ionization detector (HID) to operate in connection with capillary columns for trace gas analyses has been evaluated. Two different capillary columns were considered: a PLOT fused silica column with molecular sleve and a thick film WCOT glass column with PS-255. The determination of trace impurities in gases can be achieved with evident advantages over classical adsorption columns, even using a split injection system. Direct on-column injections also have been investigated with promising results.  相似文献   

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