Quantitative relationship and application of 3‐benzylketoimine metal dichlorides in the analysis of volatile hydrocarbons

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.     

Interpretation of interactions of halogenated hydrocarbons with modified silica adsorbent coated with 3-benzylketoimine group silane

The paper reports a new group of adsorbents obtained by modification of silica surface with silane containing 3-benzylketoimine groups with bonded Cu(II) and Ni(II) chlorides. The adsorbents obtained were subjected to a chromatographic study to establish the type of adsorbate-adsorbent interactions for aliphatic and aromatic halogenated hydrocarbons used as adsorbates. The following retention parameters were determined: retention factor (k), Kovats retention index (I), specific retention volume (V _g), and molecular retention index (ΔM _e). Values of the molecular retention index were subjected to complex statistical analysis providing qualitative relations between the adsorbates’ properties and spatial structure and their retention. It was observed that bonding of chlorides of Cu(II) and Ni(II) with the ketoimine groups resulted in an increase of the retention index and the molecular retention index indicating an increase of the adsorbate-adsorbent interaction in comparison with the reference column coated with silane including a 3-benzylketoimine group without transition metal chlorides. Along with the observed increase of the adsorbate-adsorbent interaction, larger difference between the retention indices was observed for both halogenated compounds. This indicates a positive influence of the introduced transition metals on the selectivity of the adsorbate-adsorbent interactions of the examined columns.     

Study of a monolithic silica capillary column coated with poly(octadecyl methacrylate) for the reversed-phase liquid chromatographic separation of some polar and non-polar compounds

The performance of a monolithic silica capillary column coated with poly(octadecyl methacrylate) (ODM column) for the reversed-phase liquid chromatographic separation of some polar and non-polar compounds was studied, and the results were compared to those obtained by using a monolithic silica capillary column modified with octadecylsilyl-(N,N-diethylamino)silane (ODS column). Benzene and naphthalene derivatives, polycyclic aromatic hydrocarbons (PAHs), steroids, alkyl phthalates, and tocopherol homologues were used as test samples. In general, compounds with aromatic character, rigid and planar structures, and lower length-to-breadth ratios (more compacted structures) seem to have more preference for the polymer coated stationary phase (ODM). Compounds with acidic character have also a higher retention on ODM columns because of the presence of ester groups in the stationary phase. The polymer coated column allowed the separation of some PAHs, alkyl phthalates, steroids, and of beta- and gamma-tocopherol isomers which cannot be separated under the same conditions on ODS columns, while keeping similar column efficiency. These results allowed to suggest ODM columns as a good alternative to conventional ODS columns for reversed-phase liquid chromatography.     

Equilibrium chromatographic characteristics of capillary column coated with polytrimethylpropyne for separating polar and non-polar organic compounds by gas capillary chromatography

The temperature dependence (50—180 °C) of the retention factor for 35 hydrocarbons and their oxygen-containing derivatives was studied using a capillary column coated with a new film-forming polymeric adsorbent polytrimethylsilylpropyne (PTMSP). The heats of adsorption for 24 organic polar and non-polar compounds on PTMSP were determined. They turned out to be lower than the heats of adsorption of the same compounds on Porapak Q widely used in gas chromatography. The new adsorbent PTMSP is characterized by high selectivity suitable for practical application.     

Improvement of the chromatographic separation performance of an imidazolium ionic liquid functionalized silica column by in situ anion‐exchange with dodecyl sulfonate and dodecylbenzene sulfonate anions

The anionic part of ionic liquids can provide additional interactions during chromatographic separations. In this work, the chromatographic separation performance of a silica column functionalized with 1‐propyl‐3‐methylimidazolium chloride ionic liquid was improved by in situ anion‐exchange from chloride anions to dodecyl sulfonate anions and dodecylbenzene sulfonate anions. The separation performances of these ionic liquid functionalized phases were investigated and compared with each other using polycyclic aromatic hydrocarbons, phthalates, parabens, and phenols as model compounds. Results indicated that the new columns presented a better chromatographic separation than the original one. This was ascribed retention mechanism from organic anions. The introduction of dodecyl sulfonate anions increased the hydrophobicity of stationary phase. Furthermore, the phenyl groups of dodecylbenzene sulfonate anions could provide an enhanced selectivity to aromatic compounds such as polycyclic aromatic hydrocarbons by π–π interactions. Analysis repeatability of the new columns was satisfactory (RSD of retention time, 0.10–0.40%; RSD of peak area, 0.66–0.84%).     

Influence of the carrier gas on retention factors of gaseous hydrocarbons on polytrimethylsilylpropyne using capillary gas chromatography

The retention factor and height equivalent of a theoretical plate for gaseous hydrocarbons C₁—C₄ were studied on capillary columns with the layer of the new polymeric adsorbent polytrimethylsilylpropyne (PTMSP) as functions of the nature and pressure of the carrier gas. The retention factor k increases in the series helium < nitrogen < carbon dioxide. The k values depend linearly on the average pressure of the carrier gas in a capillary column with the adsorption PTMSP layer.     

3,4-二(3-苯氧基-4-氟苯基)-2,5-二苯基苯基接枝聚硅氧烷气相色谱固定相的合成与表征（英文）

合成了一种耐高温的3,4-二(3-苯氧基-4-氟苯基)-2,5-二苯基苯基接枝聚硅氧烷(DPFP)固定相,使用静态涂渍法将其涂渍到毛细管柱内壁上,制成气相色谱柱。分离裂解乙烯的色谱图显示DPFP固定相在360℃时仍具有良好的分离能力。DPFP固定相的柱效为3 324块/米(保留因子(k)4.24,萘,0.25 mm i.d.)。麦克雷诺常数计算结果显示DPFP固定相属中等极性。溶剂化参数模型结果显示DPFP固定相与溶质之间的主要作用力为偶极-诱导偶极作用力、氢键碱性作用力。Grob试剂分离结果显示DPFP色谱柱具有良好的选择性与惰性。另外,芳香族同分异构体、苯取代物、多环芳烃、脂肪酸酯及脂肪醇都得到了良好的分离,表明DPFP固定相在应用方面有巨大的潜力。     

Studies of open tubular micro capillary liquid chromatography. 1. The development of open tubular micro capillary liquid chromatography

Micro capillary columns were successfully applied to liquid chromatography by employing the principles used in micro high performance liquid chromatography. Fundamental investigations on the use of capillary columns in LC were performed for the various column parameters. Good separations of five aromatic hydrocarbons and four kinds of phthalic esters were obtained on a 62 μm I.D. capillary column, coated with SE-30.     

气相色谱保留指数通用数据库的研究（一）PEG20M石英毛细管柱保留指数可比性的考察

测定了６１个不同类型化合物在６根ＰＥＧ２０Ｍ石英毛细管柱上的保留指数（ＲＩ），结果表明各柱间ＲＩ存在相当大的差异，给ＲＩ数据库的应用带来了困难，结合文献数据，从固定液本身、相界面吸附、热力学函数及柱极性的表征等方面探讨其原因，认为以烷烃为主的相界面吸附是影响ＲＩ可比性的重要因素，同时柱制备过程带来的影响也不容忽视。     

In situ fabrication of microporous organic network coated capillary column for high resolution gas chromatographic separation of hydrocarbons

Microporous organic networks (MONs) are a new class of porous materials synthesized via Sonogashira coupling reactions between organic building blocks. Here we report an in situ synthesis approach to fabricate MONs coated capillary column for high resolution GC separation of hydrocarbons. The McReynolds constant evaluation reveals the MONs coated capillary is a non‐polar column. The MONs coated capillary column shows good resolution for GC separation of diverse important industrial hydrocarbons such as linear and branched alkanes, alkylbenzenes, pinene isomers, ethylbenzene and styrene, cyclohexane and benzene. The MONs coated capillary column gave a high column efficiency of 1542 plates per meter for hexane and good precision for replicate separations of the selected hydrocarbons with the RSDs of 0.2–0.3, 1.5–3.1, and 1.9–3.3% for retention time, peak height and peak area, respectively. The MONs coated capillary also offered better resolution than commercial Inert Cap‐1 and Inert Cap‐5 capillary columns for hexane and heptane isomers. These results reveal the potential of MONs as novel stationary phases in GC.     

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.     

Gas chromatographic analysis of high-molecular-mass polycyclic aromatic hydrocarbons II. Polycyclic aromatic hydrocarbons with relative molecular masses exceeding 328

Three columns were used for the gas chromatographic analysis of polycyclic aromatic hydrocarbons (PAHs) with relative molecular masses (M_r) up to 450. Two of the columns were commercially available, coated with a 50% methyltrifluoropropyl-substituted polysiloxane a 5% diphenyl-substituted methylpolysiloxane. The third column was laboratory made, coated with a biphenyl-substituted silarylene-siloxane copolymer. All three columns were utilized for the analysis of high-M_r PAHs as regards both thermal stability of the stationary phases, i.e., low bleeding rate, and chromatographic efficiency. The column coated with a trifluoropropyl-substituted stationary phase showed, however, a low separation efficiency, possibly owing to low solute stationary phase compatibility. The biphenyl-substituted stationary phase, on the other hand, showed a very high separation efficiency, but the retention of the PAHs was significantly higher on this column compared with the other two, leading to the demand for higher oven temperatures. Different retention mechanisms were observed on these columns, as shown by differences in the retention indices of the PAHs measured in a system using PAHs as retention index markers. A comparatively faster elution of non-planar PAHs was observed on the columns coated with the trifluoropropyl-substituted stationary phase and the biphenyl-substituted stationary phase compared with the column coated with the 5% diphenyl-substituted polymer. The usefulness of the columns for separations of high-M_r PAHs is demonstrated by gas chromatograms of carbon black extracts and a coal tar extract standard reference material.     

Polyimide polymer glass-free capillary columns for gas chromatography

Polymeric polyimide capillary tubing, both uncoated and coated with stationary phases of two polarities, is explored for use as capillary columns for gas chromatography (GC). These glass-free polyimide columns are flexible and their small winding diameter of less than a cm around a solid support makes them compatible for potential use in portable GC instruments. Polyimide columns with dimensions of 0.32 mm i.d. × 3 m are cleaned, annealed at 300°C, and coated using the static method with phenylmethylsilicone (PMS). Separations of volatile organics are investigated isothermally on duplicate sets of polyimide columns by GC with a flame ionization detector using split injection. Unlike the uncoated ones, the coated polyimide columns successfully separate Grob test mix classes of alkanes, amines, and fatty acid methyl esters. The relative standard deviations for retention time and peak area are 0.5 and 2.5 , respectively. With the 3 m PMS-coated column connected to a retention gap to permit operation at its optimum flow rate of 30 cm/s, a plate count of 3200 or plate height of 1 mm is possible. Lack of retention and tailing peaks are evident for the polyimide polymer capillary columns as compared to that of a 3 m commercial cross-linked PMS fused silica capillary. However, headspace analyses of an aromatic hydrocarbon mix and a Clearcoat automotive paint sample are viable applications on the PMS polyimide polymer column.     

Development of a new C14 monolithic silica column containing embedded polar groups for pressurized capillary electrochromatography

Monolithic columns have been prepared with a novel bonded silica stationary phase, tetradecylamine bonded silica (TDAS), and used in pressurized capillary electrochromatography (pCEC). The monolithic silica column matrix was prepared by a sol-gel process and then chemically modified with the spacer (3-glycidoxypropyl)trimethoxysilane and tetradecylamine. The introduced embedded polar amine groups dominated the charge on the surface of the monolithic stationary phase and generated an EOF from cathode to anode under acidic conditions. The tetradecyl hydrophobic chains in TDAS provide chromatographic interactions. The chromatographic characteristics of the prepared monolithic column were studied. Some aromatic compounds including alkylbenzenes, aromatic hydrocarbons, phenols, and anilines were successfully separated on the TDAS monolithic column in pCEC mode. As expected, the TDAS monolithic stationary phases exhibit typical reversed-phase electrochromatographic behavior toward neutral solutes due to the introduced tetradecyl groups. Hydrophobic as well as electrophoretic migration processes within the monoliths were observed in the separation of basic anilines. Symmetrical peaks can be obtained for anilines because the embedded polar amine groups on the surface can effectively shield the adsorption of positively charged analytes onto the stationary phase.     

Perfusion chromatography: Effect of micropore diffusion on column performance in systems utilizing perfusive adsorbent particles with a bidisperse porous structure

A mathematical model describing single-component and multi-component adsorption in columns with bidisperse perfusive or bidisperse purely diffusive adsorbent particles is constructed and presented. The model is used to study the adsorption of lysozyme onto monocional anti-lysozyme in columns with bidisperse porous adsorbent particles. The influence of the effective pore diffusion coefficient of the adsorbate in the microparticles (microspheres) and the effects of particle size and intraparticle convective flow on column performance are examined. The results for the systems studied indicate that the systems with bidisperse perfusive particles provide a higher dynamic utilization of the adsorptive capacity of the column than the systems having bidisperse purely diffusive particles.     

Chromatographic and adsorptive properties of mercury sulfide

Summary The behaviour of mercury sulfide (metacinnabarite) as an adsorbent in gas-solid chromatography was investigated. Adsorption of some aliphatic, alicyclic, chlorimated and aromatic hydrocarbons and acetone is discussed in the light of adsorbate-adsorbent interactions. For the organic compounds used, thermodynamic parameters were determined and discussed in terms of the specific reactions that may take place on the adsorbent surface. Experimental data obtained show that mercury sulfide can be successfully employed as an adsorbent in analytical gas-solid chromatography.     

Capillary gas chromatography of some metal acetylacetonates

Summary The retention and resolution of simple mixture of Al(III), Cr(III), Co(III), and Fe(III) acetylacetonates were investigated on capillary columns coated with methyl and methyl phenyl silicones (OV-1 or OV-17) used as the stationary phase, at different column temperatures and carrier gas flow rates. Successful elution and good resolution were obtained only for the Al(III) and Cr(III) complexes, both under isothermal and programmed-temperature conditions; better resolution was observed on the column coated with OV 17.     

Graphene oxide and reduced graphene oxide as novel stationary phases via electrostatic assembly for open‐tubular capillary electrochromatography

We present here the application of graphene oxide (GO) and reduced graphene oxide (GOOH) sheet as novel stationary phases for open‐tubular CEC (OTCEC) separation based on electrostatic assembly. The inner walls of a bare capillary column was first modified by ionic assembly of poly (diallyldimethylammonium chloride) (PDDA), and then negatively charged GO or GOOH was easily assembled on a positively charged interior walls of the capillary by electrostatic force. Scanning Electron Microscope images showed that GO and GOOH can still maintain sheet‐layer‐like structure when coated onto the capillary via electrostatic assembly. The chromatographic properties of the GO and GOOH coated columns were evaluated via OTCEC separations of various kinds of analytes, including three acid nitrophenol isomers, three basic nitroaniline isomers, and four neutral PAHs. Efficient separations of all the analytes were achieved with optimized buffer pH and organic additive. The reproducibility and stability of the GO or GOOH coated columns were investigated. Our results indicate the capability of application GO or GOOH sheet in OTCEC separation, which can be coated on the inner wall of fused‐silica capillary via electrostatic assembly.     

Separation of unsaturated and aromatic hydrocarbons on capillary columns packed with barium sulphate

Summary Isomeric hydrocarbons with molecules having similar geometry but differing in the electron density distribution were separated on capillary columns packed with barium sulphate, a non-porous ionic adsorbent. Samples of BaSO₄ were washed free of foreign ions and modified by solutions of alkaline metal halides. The selectivity of the separation of unsaturated and aromatic hydrocarbons can be controlled by varying the conditions of the BaSO₄ treatment. Capillary columns packed with the ionic adsorbent were successfully used to separate all xylene and butene isomers, as well as isomers of cis and trans octene-2.     

Comparative studies of gas chromatographic properties of new packings with chemically bonded complexes

Specific interactions of aliphatic linear and branched hydrocarbons as well as cyclic and aromatic hydrocarbons with new packings containing chemically bonded complexes of transition metals are studied. The possibility of using these packings to separate these compounds is also discussed. The packings under study contain complexes of Cu(II) and Cr(III) chemically bonded to the silica surface. Chlorides of these metals are bonded to the silica surface by the use of the ketoimine group originally from 2-(3-triethoxysililpropylimino)-3-(n-buthyl)-pentanon-4. In order to determine an influence of the performed modification to gas chromatographic properties of the packings, such retention parameters as retention factor, retention index, molecular retention index, and specific retention volume are measured for these compounds. Based on the obtained values, a trial is taken to determine an influence of the nature of the bonded metal from the complex on the retention of the adsorbates under study and a dependence between a structure of an adsorbate molecule and values of charge-transfer interactions with the bonded metal complexes.