原位合成分子筛膜毛细管色谱柱的研制

吸附型多孔层毛细管柱既耐高温又对气体及烃类异构体有选择性，同时又具有毛细管色谱快速、高效等优点，是解决难分离组分的重要柱型．常用作气一固吸附色谱固定相的有强极性的硅、中极性的氧化铝、非极性的碳质及特殊吸附作用的分子筛．其中分子筛以其独特的吸附作用，在永久性气体和烃类碳数族组成分析中有重要地位．Pruecell和Soulages[1，2]等制备了涂渍型5A和13X型分子筛的毛细管柱，对低碳烃类化合物显示了良好的分离能力，分析柱温较填充柱降低约100℃．邹乃忠等[3～5]也先后制备了分子筛层的毛细管柱用来作直馏汽油的分析．由于通…     

超微粒分子筛多孔层毛细管气相色谱柱的初步研制

探讨了以超微粒分子筛成功地沉积于玻璃毛细管内壁制备出新型ＰＬＯＴ柱的方法。实验证明,这种ＰＬＯＴ柱具有快速、高效、稳定和选择分离等独到特性。     

A new bonded porous polymer PLOT U column with increased polarity

The separation features of a new type of PLOT U column are presented through many applications. This type of PLOT U column is coated with a divinylbenzene-ethylene glycol dimethacrylate copolymer. It has an increased polarity when compared with a conventional PLOT Q type column. The stationary phase of the PLOT U column is truly bonded, thus providing column rinsability and low column bleed.     

Separation of mixed halocarbons of environmental interest on a new type of silica-based porous-layer open tubular capillary gas chromatographic column

A new type of capillary porous-layer open tubular (PLOT) column consisting of a hydrophobic silica layer on a fused-silica capillary has been tested for the separation of a mixture of environmentally sensitive halocarbons present in tropospheric air. The column shows high retention for a wide range of halocarbons, with elution orders following both boiling point order and hydrogen bonding capability. The resolution of the halocarbons is good and only one pair of halocarbons [CHFClCF₃ (HCFC 124) and CH₃CF₂Cl (HCFC 142b)] cannot be resolved on this column type at all column temperature profiles. Unlike alumina PLOT columns, the silica PLOT column does not dehydrohalogenate labile halocarbons. Excellent reproducibility of retention times and peak areas for halocarbons on the column are reported.     

Rapid analysis of hydrocarbons and inert gases by a multidimensional gas chromatograph

A combination of a pressure switching system with multiple columns and photoionization detectors makes possible rapid analysis of a mixture of inorganic gases and hydrocarbons. Hydrocarbons are separated by a narrow bore capillary column. An alumina PLOT column is used for the separation of lower molecular weight hydrocarbons, especially C4 isomers, while a combination of a micro-packed column with Porapak N and a PLOT capillary column with Molecular Sieve 5A is used for the fast separation of inorganic gases. A photoionization detector is a powerful additional tool for organic gas analysis.     

分子筛改性气—液毛细管柱及其性能考察

以原位合成法制备的分子筛膜对玻璃毛细管内壁进行改性后，成功地制备了常规口径及大口径分配ＳＣＯＴ柱，并对毛细管柱的性能进行了评价。     

The fabrication of poly (polyethylene glycol diacrylate) monolithic porous layer open tubular (mono‐PLOT) columns and applications in hydrophilic interaction chromatography and capillary gas chromatography for small molecules

The easy shrinkage and swelling of polymer monolithic column when exposed to mobile phase with different polarity is a problem that cannot be ignored. To overcome this drawback, a convenient aqueous two‐phase polymerization approach was used to prepare poly (polyethylene glycol diacrylate, PEGDA) monolithic porous layer open tubular (mono‐PLOT) columns (150 μm). The poly(PEGDA) mono‐PLOT column with homogeneous polymer porous layer was synthesized successfully. A maximum plate number of 41,500 plates per meter for allyl thiourea was obtained under a velocity of 1.8 mm/s. Several kinds of polar molecule were separated on the proposed mono‐PLOT column and a typical hydrophilic interaction retention mechanism was observed. High speed separation of benzoic acids was also carried out, baseline separation of five benzoic acids was successfully achieved within 5 min with a 70 cm mono‐PLOT column at 50°C. Furthermore, the resulting PLOT column was also successfully applied to separate standard analytes of three DNA oxidative damage products and RNA‐modified nucleosides and four chlorophenols. At last, the column could separate alcohols, alkanes, and aromatic isomers via GC. It had more than 20,000 plates per meter for butanol – higher than commercial coatings open tubular columns.     

A new look at light hydrocarbon separations on commercial alumina PLOT columns: Column selectivity and separation

Alumina-coated porous layer open tubular (PLOT) columns are widely used for analyses of light hydrocarbons (C₁ to C₆). There is, however, a need for improved selectivity for complex analyses such as the determination of impurities in high purity petrochemical products. Some commercial alumina PLOT columns do not have sufficient selectivity for such analyses. The selectivity of four commercial alumina PLOT columns is evaluated for analyses of propylene and ethylene, and differences in column selectivity discussed. Requirements of column selectivity and retention are presented for several applications including the analysis of refinery gas, transformer oil gas, and fuel gas.     

新型聚合物多孔涂层毛细管开管柱的制备及电色谱研究

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%。     

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。     

Chromatographic properties of open tubular columns with an adsorption layer of aerosil

The chromatographic properties of a porous layer open tubular (PLOT) capillary column with an adsorption layer of highly dispersed silicon dioxide (Aerosil) were studied. It was found that the high efficiency and capacity of the column were retained at high rates of a gas-chromatographic process. The test adsorbent is similar to polydimethyl and polyphenylmethyl siloxane stationary phases in terms of selectivity. Complex multicomponent hydrocarbon mixtures can be separated on the PLOT/SiO₂ column because of low peak asymmetry.     

In-situ Preparation of Integrated Polymeric Pora-U PLOT Columns and their Applications in Gas Chromatography

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.     

Stainless steel capillary columns for high temperature gas chromatography

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.     

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.     

窄内径多孔层开管柱的制备及在液相色谱中的应用

近年来,微纳分离技术由于其内在的优势而受到越来越多的关注.多孔层开管柱是一种重要的微分离柱形式,与粗内径的多孔层开管柱(>25μm)相比,窄内径的多孔层开管柱具有更高的分离效率和更低的试剂消耗量.本文综述了内径≤25μm的窄内径多孔层开管毛细管柱的制备方法、与质谱检测联用技术以及在液相色谱中的应用研究进展,对其发展前景进行了展望.     

Capillary electrochromatography of amino acids with a protein-bonded porous-layer open-tubular column

A protein-bonded porous-layer open-tubular (PLOT) column has been synthesized and applied to the separation of amino acids by CEC. The porous layer was coated on the capillary inner wall by in situ polymerization of 2-hydroxyethyl methacrylate and 2-vinyl-4,4-dimethylazlactone in the presence of 1-decanol as a porogen inside a fused-silica capillary silanized with gamma-methacryloxypropryltrimethoxysilane. The azlactone functionalities at the surface of the porous polymeric support layer were allowed to react with BSA to yield a protein-bonded PLOT column. This porous layer was characterized by scanning electron microscopy and its thickness was about 1 microm. CEC on this column gave enhanced resolution of three amino acids (histidine, phenylalanine, and tryptophan), and baseline separation was achieved with 20 mM phosphate buffer, pH 8.0.     

In-situ chemical investigation of a comet nucleus by gas chromatography: Porous layer open tubular columns for the separation of light, volatile compounds

Summary In the framework of the cometary sampling and composition (COSAC) experiment of the European Space Agency (ESA) Rosetta space mission to a comet, a new generation of porous polymer porous-layer open tubular (PLOT) columns has been investigated with the aim of separating the light organic compounds targeted by the experiment within the constraints of the operating conditions used in space. Both styrene-divinylbenzene and ethylene glycol-dimethyl acrylate-divinylbenzene porous polymers can be used to separate most of the target compounds, but the latter was selected because of its better separating properties. The most appropriate column characteristics were found to be 10 m length, 0.18 mm internal diameter, and 1–2 μm layer thickness, despite the low sample-loading capacity of such a column, which impairs its chromatographic performance. The influence of column overloading on retention properties and efficiency was, therefore, studied. To achieve the separation with optimum sensitivity, and within the in-situ time allowed for the analysis, it was also demonstrated that the maximum allowed temperature and reduced outlet pressure are required. Finally, it was shown that in the presence of water, the most abundant volatile compound in comets the separating properties of the studied columns are conserved. This paper thus demonstrates the suitability of the porous polymer PLOT column selected for the COSAC experiment and requirements for use in space; it is the first porous polymer PLOT column to be used in space exploration. Presented at: 23^rd International Symposium on Chromatography, London, UK, October 1–5, 2000     

聚二乙烯苯整体柱的制备及其在气相色谱分析中的应用

初步探讨了毛细管整体柱的制备方法及其在气相色谱分析中的应用。以液相色谱用毛细管整体柱作为研究基础,通过改变甲苯和十二醇的比例,使整体柱适用于气相色谱分析。通过二乙烯苯与键合在管壁上的3-(异丁烯酰氯)丙基三甲氧基硅烷(TMP)键合以及其自身的聚合,获得具有牢固结构、良好机械强度的整体柱。将其用于混合溶剂的分析和白酒标样的分析,可直接分析水中低碳醇。与现有的商品柱进行比较,结果表明所制备的整体柱均优于用以对照的商品色谱柱,其中在混合溶剂的分析中,醇类、酯类、酮类和芳烃类的峰形均优于用于比较的多孔层开口管(PLOT)柱;在白酒标样分析中,使得乙醛、甲醇、乙酸乙酯的色谱峰能够分开,比现有的聚乙二醇(PEG-20M)柱的分析方法更为便捷。     

Estimation of Olefin Dimerisation Products by GC/GC–MS and IR Techniques

A GC and IR based protocol was developed for monitoring the isobutene dimerisation process wherein the complete characterisation of the products was carried out by GC coupled with mass spectrometry. In the dimerisation process, LPG from FCC process comprising a mixture of saturated and unsaturated C4 hydrocarbons is subjected to a dimerisation process using a catalyst to produce C8 hydrocarbons. The reaction is carried out keeping in view the demand for high-octane blending components in gasoline. The isooctene generated in the process (mainly from the dimerisation of isobutene) is converted into isooctane having the RON and MON value 100. The monitoring process requires the use of two different column chemistries, viz., a 100 m CPSIL PONA CB non-polar column for C8 and its isomers and an Alumina PLOT column for C4 hydrocarbons. A 100 m non-polar column does not separate the C4 mixture since the column is meant for gasoline range products containing C5 and above hydrocarbons. Therefore, a need was felt for an improvised method which can handle both the analyses simultaneously. A cryogenic oven program starting from 0 °C was developed for separating the isomers of C4 hydrocarbons and C8 hydrocarbons on a single column during the single run by Detailed Hydrocarbon Analyzer. The data obtained using the cryo programme was validated with data obtained using Alumina PLOT column on C4 mixture since the Alumina PLOT column is the widely accepted column chemistry for separating the C4 hydrocarbons. An IR method for the estimation of the total olefin content was developed using 2,2,4-trimethyl pentene-1 as the reference standard. The total olefins generated during the process were identified by GC–MS, quantified by DHA-FID and validated by infrared spectroscopy. A good correlation was found between GC and IR spectral results (correlation coefficient R ²  = 0.99).     

Peak tailoring concept in gas chromatographic analysis of volatile organic pollutants in the atmosphere

An automated gas chromatographic system aiming at performing unattended analysis of volatile organic compounds (VOCs) was developed in laboratory. To encompass VOCs of a wide range of volatility, two different designs of enrichment and separation methods were adopted and compared with performance in analyzing ozone precursors of C3-C12. In the dual-trap dual-column design, lower boiling species (C3-C6) are enriched and separated by one set of trap and column (porous layer open tubular (PLOT)), whereas the enrichment and separation for the higher boiling species (C6-C12) are performed by the other set (wall-coated open tubular (WCOT)). Undesired peaks also inevitably appear on both chromatograms often causing annoyances. To reduce complexity of both the apparatus and the resulting chromatograms, the heart-cut technique was adopted as a base for developing a system, which only uses one trap and one flame ionization detector for constructing two-dimensional GC with PLOT and DB-1. Methods were developed to allow the auxiliary flow pressure in the heart-cut device to be programmed to create dual effects, which not only can perform regular heart-cut actions but can also temporally hold up species in the precolumn for prescribed time intervals. Because it is characteristic for PLOT chromatograms to have reproducible blank retention time windows, segments of a DB-1 trace are produced by the auxiliary flow program aligning perfectly in time with the gaps of the PLOT trace. Subsequently, the two column flows are merged and channeled into single flame ionization detector to produce a very condensed "tailored" chromatogram which is equivalent to overlaying a PLOT and a DB-1 chromatogram on top of each other, except that no peaks are overlapped. This innovative "peak tailoring" concept based on the heart-cut technique is simple in design, easy to build, and extremely rugged for long-term continuous operation as fewer moving parts are involved, which is beneficial for deploying in remote monitoring stations.