多壁碳纳米管作为气相色谱固定相的性能研究

将甲烷催化裂解法生产的经过纯化的多壁碳纳米管(PMWCNTs)、活性炭、石墨 化碳黑(Carbopack B)分别填装成气相色谱填充柱,比较它们分离烷烃、芳香烃、 卤代烃、醇、酮、醚、酯类的性能。分别在PMWCNTs和Carbopack B上涂清5%(w/w) 的Carbowax 20M,填装成气相色谱填充柱后,比较它们分离醇、酮、醚、酯、有机 酸类的性能。结果表明,PMWCNTs是一种性能优异的气相色谱固定相。与相同比表 面积的Carbopack B石墨化碳黑相比较,它有更强的保留能力,适合于分析沸点相 对较低的化合物;具有更均匀的表面,表现为极性化合物亦可得到对称的峰形;理 论塔板数较小。此外,和Carbopack B一样,PMWCNTs涂清5% (w/w) Carbowax 20M 后可用来分离极性化合物,甚至是强极性的小分子有机酸。     

多壁碳纳米管的纯化

用900℃高温氢气处理以及5 mol/L盐酸回流的方法，纯化了一种由甲烷在Ni- Mg-O催化剂上裂解生长的多壁碳纳米管（MWCNTs），考察了不同纯化阶段MWCNTs的 吸水率、比表面积、Ni和Mg残留量以及在不同温度下苯、正己烷、乙醇、丙酮四种 化合物在MWCNTs填充色谱柱上的脱附率的变化，并用透射电镜观察了MWCNTs的形态 。结果表明，高温氢气处理可去除MWCNTs的无定形碳和表面极性基团，使其比表面 积和吸水率减小，同时可打开MWCNTs端口。高温氢气处理后，再用盐酸回流即容易 去除MWCNTs中单用盐酸回流方法无法去除的Ni.经过纯化的MWCNTs的吸水率远小于 活性碳，比Carbopack B稍大，比表面积和Carbopack B相近。苯、正己烷、己醇、 丙酮四种化合物在纯化的MWCNTs填充色谱柱上的脱附率和Carbopack B的相同。经 纯化的MWCNTs的Ni残留量为30 μg/g，Mg残留量低于检测限（10 μg/g）。由于管 腔的存在，纯化的MWCNTs对有机物的保留能力大于Carbopack B。它可以作为气相 色谱固定相和吸附挥发性有机物的吸附剂。     

Evaluation of multi-walled carbon nanotubes as an adsorbent for trapping volatile organic compounds from environmental samples

A type of purified multi-walled carbon nanotubes (PMWCNTs) prepared by catalytic decomposition of methane, with a surface area of 98 m2/g, was evaluated as an adsorbent used for tapping volatile organic compounds (VOCs). The performance in evaluation was based on breakthrough volumes (BTVs) and recoveries of selected VOCs. PMWCNTs were also used as a trap packing material to adsorb VOCs purged from spiked water sample. Due to their porous structure, PMWCNTs were found to have much higher BTVs than that of Carbopack B, a graphitized carbon black with the same surface area as PMWCNTs. The recoveries of the tested VOCs trapped on PMWCNTs ranged from 80 to 110%, and not affected by the humidity of purge gas. The results indicate that PMWCNTs are a potential useful adsorbent for direct trapping VOCs from air samples and may be a supplement to VOCARB 3000, a commercially available trap, in purge-and-trap system to preconcentrate VOCs from water samples.     

Gas chromatography of hydrocarbons using packed liquid chromatographic capillary columns

Capillary columns of 0.3-0.5 mm i.d. packed with 3- to 30-μm silica-based stationary phases for liquid chromatography were used for gas chromatographic separation of hydrocarbons. Column efficiencies were evaluated for various commercially available packing material. The best column efficiency was achieved with 5-μm octadecyl group bonded silica gel, the surface of which was coated with a poly (dimethylsiloxane) film. The 30-cm column produced 11,000 theoretical plates.     

The determination of chlorinated aliphatic hydrocarbons in air, natural waters, marine organisms, and sediments

A gas Chromatographic procedure is described for the determination of chlorinated aliphatic hydrocarbons in the atmosphere, natural waters, aquatic organisms and sediments. Air samples are passed through activated carbon traps and the chloro compounds are later desorbed by heating in a current of nitrogen. Chloro compounds are stripped from water samples by bubbling with nitrogen and from bio-materials and sediments by heating in a current of nitrogen. In each instance, the chlorinated compounds are trapped in copper columns packed with Chromosorb coated with silicone oil, and cooled to -78°. The chloro compounds are subsequently swept off these columns into a gas chromatographic column with a current of argon. Detection of the Chromatographic peaks is performed with an electron-capture detector. The procedure gives near quantitative recoveries of a range of chlorinated hydrocarbons from natural samples.     

GC investigation of olefins with chemically bonded gamma-mercaptopropylsilane-copper(II) complexes

Summary A column packing containing thiol groups chemically bonded to the silica surface was synthesized. The thiol functional groups were used as ligands capable of forming stable complexes with Cu(II). The prepared material was characterized by gas chromatography using unsaturated linear and branched hydrocarbons as well as cyclic and aromatic hydrocarbons. The occurrence of specific metal—olefin interactions resulting from the formation of -complexes during the chromatographic process was observed.Part IV of a series on transition metal complexes in GC. Part III see ref. [1].     

Capillary column coated with graphene oxide as stationary phase for gas chromatography

The graphene oxide (GO) is carbon based material that has high surface area, high adsorption ability, and is stable at high temperature. In this work, the GO phase was prepared and used for gas chromatographic separation. GO nanosheets were covalently bonded onto the inner surface of fused silica capillary column using 3-aminopropyldiethoxymethyl silane as cross-linking agent. The prepared GO nanosheets were characterized with TEM and the GO coating was characterized with SEM. As a high performance stationary phase, GO provides not only a high surface area to increase the phase ratio but also rich functional groups for the formation of hydrophobicity, hydrogen bonding, and π–π electrostatic stacking interactions with volatile aromatic or unsaturated organic compounds. Thus, mixtures of a wide range of organic compounds including alcohols and aromatic compounds were well separated and an efficiency of 1990 theoretical plates per meter for anisole was obtained on GO coated 1.0 m × 200 μm i.d. fused silica capillary column. The experimental results demonstrate that GO coated capillary columns are promising for gas chromatographic separation.     

Measurements Of Biogenic Hydrocarbons And Their Atmospheric Degradation In Forests

Abstract

An analytical procedure for the sampling and quantitative determination of biogenic hydrocarbons in the atmosphere is presented. The method is based on the adsorptive preconcentration of the hydrocarbons using Tenax TA/Carbopack B filled sampling tubes followed by thermodesorption of the trapped compounds and gas chromatographic analysis. To avoid losses of the biogenic alkenes as a consequence of their reaction with ozone on the adsorbents during the sampling step, an ozone scrubber is used in front of the adsorption tubes. Diurnal variations of the monoterpene- and ozone-concentrations are determined at different heights in and above a forest stand (coniferous and deciduous trees) in the Vosges (Col du Donon, 760 m a.s.l.) in order to elucidate the importance of terpene-oxidation reactions on the formation of peroxidic products in forest air.     

Improvements in the gas chromatographic determination of trace amounts of aliphatic amines in aqueous solution

The analysis of aliphatic amines at the parts per million level in aqueous solution has been improved with respect to a previously reported chromatographic method which made use of Carbopack B modified with 0.8% potassium hydroxide and 4% PEG 20M by altering these concentrations to 0.3% and 4.8%, respectively, by using a modified coating procedure. By this means, difficulties in duplicating from batch to batch the chromatographic characteristics of the column packing have been eliminated, and the instability of the retention times of amines on prolonged use of the column, the intolerance of the packing to injections of water and overlapping of tailed peaks for alcohols with the amine peaks no longer affect the trace determination of amines.     

Sampling of benzene in tar matrices from biomass gasification using two different solid-phase sorbents

Biomass tar mainly consists of stable aromatic compounds such as benzene and polyaromatic hydrocarbons, benzene being the biggest tar component in real biomass gasification gas. For the analysis of individual tar compounds, the solid-phase adsorption method was chosen. According to this method, tar samples are collected on a column with an amino-phase sorbent. With a high benzene concentration in biomass tar, some of the benzene will not be collected on the amino-phase sorbent. To get over this situation, we have installed another column with activated charcoal which is intended for collection of volatile organic compounds, including benzene, after the column with the amino-phase sorbent. The study of maximal adsorption amounts of various compounds on both adsorbents while testing different sampling volumes led to the conclusion that benzene is a limiting compound. The research proved that the use of two sorbents (500 mg + 100 mg) connected in series allows for assessment of tar in synthesis gas with a tar concentration up to 30-40 g m(-3), which corresponds to the requirements of most gasifiers.     

Multi-adsorbent preconcentration/focusing module for portable-GC/microsensor-array analysis of complex vapor mixtures

A small multi-adsorbent preconcentration/focusing module for a portable GC with microsensor-array detector designed to determine complex mixtures of volatile and semi-volatile organic compounds encountered in indoor working environments is described. Candidate adsorbents were assessed on the basis of analyte thermal-desorption bandwidth and efficiency, chromatographic peak shape, and breakthrough volume against mixtures of organic compounds ranging over four orders of magnitude in vapor pressure. A capillary packed with just 12.3 mg of adsorbent material comprising Carbopack B (8 mg), Carbopack X (2.5 mg) and Carboxen 1000 (1.8 mg) provided the best tradeoff in operating variables, while maintaining sufficient capacity for a 1 L air sample containing a mixture of up to 43 compounds, each at 100 parts-per-billion, at an ambient relative humidity of up to 100%. On-column focusing and temperature programming were used to enhance chromatographic separations, and detection limits as low as 100 parts-per-trillion were achieved for a 1 L air sample using an integrated array of polymer-coated surface-acoustic-wave (SAW) sensors. Implications for field analysis of indoor air quality are emphasized.     

Analysis of gases containing inorganic and organic compounds using a combination of a thick-film capillary column and a packed adsorption column

A gas chromatographic system consisting of one multiport valve, two (hot-wire and flame-ionization) detectors and two analytical columns (one thick-film capillary and one packed adsorption column) is used for the analysis of gas samples containing a number of inorganic compounds (hydrogen, argon, oxygen, nitrogen, carbon monoxide, and carbon dioxide) and organic compounds. Examples include samples containing hydrocarbons up to n-nonane and benzene and toluene. The system also permits the analysis of more complicated samples containing, for example, alcohols, in addition to hydrocarbons.     

Needle trap micro-extraction for VOC analysis: Effects of packing materials and desorption parameters

Combining advantages of SPE and SPME needle trap devices (NTD) represent promising new tools for a robust and reproducible sample preparation. This study was intended to investigate the effect of different packing materials on efficacy and reproducibility of VOC analysis by means of needle trap micro extraction (NTME). NTDs with a side hole design and containing different combinations of PDMS, DVB and Carbopack X and Carboxen 1000 and NTDs containing a single layer organic polymer of methacrylic acid and ethylene glycol dimethacrylate were investigated with respect to reproducibility, LODs and LOQs, carry over and storage. NTDs were loaded with VOC standard gas mixtures containing saturated and unsaturated hydrocarbons, oxygenated and aromatic compounds. Volatile substances were thermally desorbed from the NTDs using fast expansive flow technique and separated, identified and quantified by means of GC–MS. Optimal desorption temperatures between 200 and 290 °C could be identified for the different types of NTDs with respect to desorption efficiency and variation. Carry over was below 6% for polymer packed needles and up to 67% in PDMS/Carboxen 1000 NTDs. Intra and inter needle variation was best for polymer NTDs and consistently below 9% for this type of NTD. LODs and LOQs were in the range of some ng/L. Sensitivity of the method could be improved by increasing sample volume. NTDs packed with a copolymer of methacrylic acid and ethylene glycol dimethacrylate were universally applicable for sample preparation in VOC analysis. If aromatic compounds were to be determined DVB/Carboxen 1000 and DVB/Carbopack X/Carboxen 1000 devices could be considered as an alternative. PDMS/Carbopack X/Carboxen 1000 NTDs may represent a good alternative for the analysis of hydrocarbons and aldehydes. NTME represents a powerful tool for different application areas, from environmental monitoring to breath analysis.     

键合石墨化碳黑作为毛细管气相色谱固定相的研究

将石墨化碳黑衍生物键合在毛细管柱上,对烷烃、醇、芳香化合物、酮类等物质进行分离考察,其色谱性能较好.键合石墨化碳黑作为毛细管气相色谱固定相使用寿命增加,可做进一步研究.     

Planar microchromatographic columns for gas chromatography

The adsorption and selective properties of aluminum-based planar microcolumns filled with the Carbopack B adsorbent are studied. The effect of geometrical parameters of the columns on their chromatographic properties is considered on an example of the separation of a mixture of light hydrocarbons. The advantages of planar microcolumns compared to conventional packed chromatographic columns are revealed.     

甘脲和羟基葫芦[6]脲气相色谱固定相的制备及其色谱分离性能比较研究

甘脲是羟基葫芦[6]脲(HOCB6)的前体, 本文设计了一种在酸性条件下均匀涂渍固定液的新方法, 首次将甘脲和羟基葫芦[6]脲用作气相色谱固定相. 将甘脲和HOCB6填装成气相色谱填充柱后, 以烷烃、卤代烃、芳香烃、醇、酮、酯、酸、胺等物质为探针, 用复杂样品花露水对它们的色谱分离性能进行了比较研究. 结果表明, 甘脲和HOCB6 都是良好的气相色谱固定相, 热稳定性高, 柱性能稳定. 两种固定相对以上溶质探针都有较好的分离能力, HOCB6固定相(PSP)与甘脲固定相(GSP)相比较, 总体上具有更好的分离选择性, 对难分离的芳香族位置异构体(如二甲苯、甲基苯胺)具有良好的分离能力, 显示出较高的立体选择性, 对花露水中的高沸点组分有较好的分离效果. 上述研究也表明, 由于溶质在载气中传质比葫芦脲内腔快得多, 全包结尽管有利于提高分离选择性, 但展宽后的柱效不理想; 适当的高柱温既保留了部分包结作用, 同时存在端口协同作用, 能兼顾高选择性和高柱效.     

The use of silicalite as a column packing for steam-solid chromatography

Chromatographic-grade silica gel can be converted to a form of the high-silica zeolite silicalite-1, which is suitable for use as a gas chromatographic column packing and can be used with steam as carrier gas in a suitably modified chromatograph. The material has the expected molecular sieve properties and lends itself to some novel separations based on molecular size and shape. The behaviour of lower aliphatic alcohols and chlorohydrocarbons, acetone and xylenes is reported.     

厚朴酚键合硅胶液相色谱固定相的制备、表征与性能评价

通过γ-巯丙基三甲氧基硅烷(KH-590)的作用, 将具有抗菌功能的中草药厚朴的主要药用成分厚朴酚键合在硅胶表面上, 制备了厚朴酚键合硅胶液相色谱固定相. 采用红外光谱、元素分析和热重分析对该固定相进行了表征. 以苯同系物、5种吡啶、6种苯胺和8种芳香羧酸类化合物为溶质探针, 初步考察了该新型固定相的基本色谱性能, 研究了其对这些化合物的保留机理. 结果表明, 该固定相的反相色谱性能类似于十八烷基键合硅胶固定相(ODS), 分离原理与疏水性作用有关; 另外, 该固定相包含有别于疏水性作用的氢键作用、π-π电荷转移作用和偶极-偶极等作用, 多种作用力使其在分离某些可电离的碱性和酸性化合物时表现出更好的选择性和分离效果. 厚朴酚配体的多种作用位点对快速分离极性芳香化合物有重要贡献.     

两种新型反相高效液相色谱填料疏水选择性能的比较

以层接层自组装法制备的TiO2/SiO2和ZrO2/SiO2微球为基质,分别与十八烷基三氯硅烷在甲苯溶液中加热回流36 h 制备了两种碳十八键合固定相。两种固定相的含碳量分别为11.51%和9.62%。对两种固定相的作用机理进行研究,并以9 种芳香类化合物对其色谱性能进行评价。结果表明,两种固定相都是较好的反相固定相,其疏水选择性差异不大,对芳香 性化合物均有较好的选择性,TiO2/SiO2的含碳量略高于ZrO2/SiO2。     

Standardized test mixture for the characterization of comprehensive two-dimensional gas chromatography columns: the Phillips mix

A novel column characterization test mixture is developed for use in comprehensive two-dimensional gas chromatography (GC x GC). This mixture has been named the "Phillips mix" in honor of the late professor John B. Phillips, the father of GC x GC. The mixture comprises a series of homologous compounds from structural groups that cover a volatility and polarity range that is similar to the Grob mix, and includes saturated hydrocarbons (alkanes), unsaturated hydrocarbons (alkenes and alkynes), carbonyls (ketones and aldehydes), primary alcohols, fatty acid methyl esters, alkyl ethers, carboxylic acids, aromatics, as well as other unique functional groups (such as amines, etc.). Similarly to the Grob mix in conventional one-dimensional GC, the Phillips mix can be used as a standardized test for performance characterization of GC x GC column sets. Unlike the Grob mix, however, the Phillips mix's most important use is as a practical guideline for column users. This paper addresses some qualitative aspects of the use of the Phillips mix through an investigation of the chromatographic fingerprints of two different GC x GC column combinations.