Preparation and characterization of hyperbranched polyester capillary columns used for the separation of basic proteins

A series of hyperbranched polyesters with pentaerythritol as the core were synthesized and coated on the inner surface of fused‐silica capillaries by chemical bonding. Three kinds of basic proteins were selected for studying the behavior of the adsorption to fused‐silica capillaries. Comparative studies of the coating materials were conducted, and the experimental results showed that the coated columns with hyperbranched polyesters could suppress the electroosmotic flow greatly and effectively prevent adsorption in the pH range of 4–6; they were superior to capillaries coated with traditional hydroxypropyl cellulose. Furthermore, research was conducted to study the effect of hyperbranched polyester generation on the column efficiency. The results showed that higher column efficiency was obtained on a capillary column coated with the sixth generation of the hyperbranched polyester at pH 5.0. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Evaluation of capillary pore size characteristics in high-strength concrete at early ages

The quantitative scanning electron microscope-backscattered electron (SEM-BSE) image analysis was used to evaluate capillary porosity and pore size distributions in high-strength concretes at early ages. The Powers model for the hydration of cement was applied to the interpretation of the results of image analysis. The image analysis revealed that pore size distributions in concretes with an extremely low water/binder ratio of 0.25 at early ages were discontinuous in the range of finer capillary pores. However, silica-fume-containing concretes with a water/binder ratio of 0.25 had larger amounts of fine pores than did concretes without silica fume. The presence of larger amounts of fine capillary pores in the concretes with silica fume may be responsible for greater autogenous shrinkage in the silica-fume-containing concretes at early ages.     

Quantitative determination of BHT in soap products by capillary gas chromatography

A simple and rapid capillary gas chromatography (GC) method is described for the quantitative determination of 2,6-di-tert-butyl-4-methylphenol (BHT) antioxidant in soap bars, fatty acids, and related intermediates. The procedure involves blending the sample with dimethylformamide in the presence of 2,4-di-tert-butylphenol (DTBP) internal standard, filtering the mixture, silylating an aliquot with BSTFA (bis-trimethylsilyltrifluoroacetamide) and quantifying by capillary GC using flame ionization detection. The silyl derivatization and nonpolar capillary column (12 m, methyl silicone, fused silica) provided resolution of BHT from certain fragrance component interferences. The method has a detection limit of approximately 10 ppm. Soaps fortified with BHT showed recoveries of 97.1±3.7% at the 200 ppm level and 92.3 ± 2.2% when spiked at the 75 ppm level. The effect of bar soap storage time on BHT content is also demonstrated.     

Determination of Rancidity of Edible Fats by Headspace Gas Chromatographic Detection of Pentane

Headspace gas analysis with a fused silica capillary PVMS 50 M column was examined for the quantitative determination of some volatile alkanes particularly pentane in edible oils. The relationship between chromatographic peak areas and pentane added in various concentrations was linear between 0.5 and 10 ppm. Significant correlations between sensory evaluation and concentration of pentane were found.     

Porous polystyrene-based monolithic materials templated by semi-interpenetrating polymer networks for capillary electrochromatography

Porous polystyrene-based monolithic columns were engineered through the in-situ generation of poly(?-caprolactone) (PCL)/polystyrene (PS) semi-interpenetrating polymer networks (semi-IPNs), followed by the extraction of the uncrosslinked partner acting as a polymeric porogen. In a first stage, the semi-IPNs were prepared within the confines of fused silica capillaries by UV-initiated free-radical copolymerization of styrene and divinylbenzene, in the presence of PCL oligomers. In a second stage, the quantitative extraction of uncrosslinked oligoesters led to the formation of porous frameworks with a hierarchical porosity, as evidenced by SEM and DSC-based thermoporometry. Such as-obtained porous monoliths could be efficiently used as reversed-phase stationary phases for the separation of alkyl benzene derivatives by capillary electrochromatography (CEC).     

Surface phenomena in capillary flow of polymer solutions

Evaluations of apparent slip and polymer adsorption are reported for laminar capillary flow of dilute aqueous solutions of the three homologues WSR 301, Coagulant and FRA of Polyox. Measurements were carried out using glass tubes coated with a silane compound (dimethyldiethoxysilane) as well as for the untreated glass tubes. The results indicate that flow enhancement is dominant at the very low polymer concentrations and flow retardation is dominant at the higher concentrations comprising the polymer concentration range investigated. A transition from a positive to a negative effective velocity at the wall was observed with increasing polymer concentration. A new analysis was applied to separate the contributions of polymer adsorption and slip in the evaluation of the effective velocity at the wall. Effective hydrodynamic thicknesses of the adsorbed polymer layers are presented as a function of the polymer molar mass and concentration and the wall shear stress. The thickness of the adsorbed layer at zero shear was also evaluated from the capillary flow data.     

Quantitation in the analysis of transesterified soybean oil by capillary gas chromatography 1

A rapid quantitative capillary gas Chromatographic method has been developed for studying transesterification of soybean oil (SBO) to fatty esters. Standard solutions containing methyl linoleate, mono- , di- and trilinolein were analyzed with a 1.8 m X 0.32 mm SE- 30 fused silica column. The effect of carrier gas flow on reproducibility was determined. Prior to analysis, mono- (MG) and diglycerides (DG) were silylated with N,O- bis(trimethylsilyl) trifluoroacetamide.Tridecanoin was used as an internal standard. From plots of area and weight relationships, slopes and intercepts for all four compound classes were determined. Agreement between the measured and calculated compositions of the standard solutions was good; the overall standard deviation was 0.4. Slopes and intercepts also were determined for SBO and its methyl and butyl esters. Complete separation of ester, MG, DG and triglyceride was obtained in 12 min by temperature programming from 160 to 350 C. This method of analysis gave excellent results when used in a kinetic study of SBO transesterification. 1 Presented at the AOCS meeting in Philadelphia in May 1985. 2 Retired biometrician, North Central Region, Agricultural Research Service, USDA. 3 Deceased     

Direct pyrolysis mass spectrometry of chlorine-containing polymers using capillary GC/MS

A direct pyrolysis mass spectrometric technique has been developed and applied to several chlorine-containing polymers. The capillary column in the gas chromatograph has been replaced by uncoated fused silica tubing to avoid the problem of column degradation induced by the polymer pyrolyzates. Under appropriate conditions, the pyrolysis mass spectra were found to be highly reproducible and to serve as “fingerprints.” The technique can be readily applied to carbon-black-filled, crosslinked elastomers, as well as polyblends and composites. The quantitative aspects of the technique have also been addressed.     

Preparation of homogeneous CNT coatings in insulating capillary tubes by an innovative electrochemically-assisted method

Preparation of homogeneous CNT coatings in insulating silica capillary tubes is carried out by an innovative electrochemically-assisted method in which the driving force for the deposition is the change in pH inside the confined space between the inner electrode and the capillary walls. This method represents a great advancement in the development of CNT coatings following a simple, cost-effective methodology.     

Comparison of high-temperature gas chromatography and CO2 supercritical fluid chromatography for the analysis of alcohol ethoxylates

This work compares capillary supercritical fluid chromatography (SFC) and capillary high-temperature gas chromatography (HTGC) for the quantitative characterization of nonionic alcohol ethoxylate surfactants. Supercritical fluid chromatographic separations of the alcohol ethoxylates were obtained with a density-programmed carbon dioxide mobile phase and a fused silica capillary column. High-temperature gas chromatographic separations were obtained with a high-temperature polyimide-coated fused silica capillary column. In addition, a procedure was developed for the quantitation of the capillary chromatographic data using flame ionization molar response factors based on the effective carbon theory. The alcohol and ethoxylate distributions, mean molecular weights and average moles of the ethylene oxide are rapidly calculated from the chromatographic data. Advantages and limitations of SFC and HTGC procedures are illustrated and discussed. Based on this work, the following conclusions can be drawn: i) For routine quality control analyses of known alcohol ethoxylates, SFC and HTGC appear to be equally applicable. ii) SFC has the advantage of time because derivatization is not required, although derivatization does improve resolution. iii) HTGC has the advantage of resolving C₁₂ through C₁₈ alcohol ethoxylate oligomers, avoiding ambiguous identification of components. iv)SFC and HTGC both have disadvantages. SFC has a resolution limitation and HTGC discriminates against high molecular-weight components. Presented in part at the 83rd Annual Meeting in Chicago, IL, May 1991.     

石英毛细管反应器内双酚A在高温水中的稳定性

引言双酚A(bisphenol A,BPA)是一种重要的有机中间体,是生产聚碳酸酯(PC)树脂及环氧(EP)树脂的主要原料。工业上BPA由苯酚和丙酮缩合而成,现也可通过解聚废弃聚碳酸酯回收得到。聚碳酸酯、环氧树脂作为食品容器或生物材     

毒死蜱乳油中有害物治螟磷的分析

建立毒死蜱乳油中有害物治螟磷的分析方法.OV-101为固定液的石英毛细管柱,邻苯二甲酸二异丁酯为内标物.实验表明:该方法在一定质量浓度范围内成良好的线性关系,线性相关系数为0.9995;标准偏差为0.004,变异系数为2.395%;平均回收率为99.5%.     

Synthesis of hyperbranched poly(3‐methyl‐3‐hydroxymethyloxetane) and their application to separate basic proteins by adsorption coated column

A series of hyperbranched poly(3‐methyl‐3‐hydroxymethyloxetane)s with different degree of branching were synthesized using BF₃·OEt₂ as initiator and coated on the inner surface of the fused‐silica capillaries. In the pH range of 3–9, the coated capillaries reduced electro‐osmotic flow by about four times lower than the bare fused‐silica capillary. The coated capillaries also displayed good resistance to adsorption of cationic proteins, providing clean separations of a mixture of Lysozyme, Cytochrome c, and Ribonuclease A around pH 3–6 in phosphate buffer. The separation efficiency in terms of peak shape was excellent compared with bare fuse‐silica capillary. The separation efficiency of hyperbranched poly(3‐methyl‐3‐hydroxymethyloxetane) with degree of branching of 0.43‐coated capillary column for Lysozyme reached 10⁶ plates/m with a resolution of 7.1, and the coated capillary column had good migration time reproducibility. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Determination of low level trans unsaturation in physically refined vegetable oils by capillary GLC — Results of 3 intercomparison studies

The analytical performance of capillary gas‐liquid chromatographic (GLC) methods for the quantitative determination of trans fatty acids (TFA) in physically refined rapeseed and soybean oils was evaluated by 3 intercomparison studies. The participants were allowed to use their own methodology regarding derivatization and GLC conditions and were not requested to follow a fixed method protocol. However, certain requirements relating to the separation efficiency (chromatographic separation of critical pairs) and the accuracy (validation of the response factors using a certified reference material) of the method(s) applied, had to be fulfilled. All 12 participating laboratories employed fused silica capillary columns coated with cyanopropyl polysiloxane for the separation of fatty acid methyl esters. Analytical precision was sufficient (relative standard deviation for reproducibility 13%) for the quantification of trans isomers occurring at levels >0.1 g/100 g in physically refined vegetable oils, i.e. trans isomers of linolenic acid. For TFA levels <0.1 g/100 g (trans isomers of oleic and linoleic acid) precision dropped sharply (relative standard deviation for reproducibility >30%).     

毛细管气相色谱法分析异丙草胺·莠悬浮剂

采用内涂OV - 1固定液的石英毛细管气相色谱柱和FID检测器 ,以邻苯二甲酸二丁酯为内标物 ,在适宜的条件下对异丙草胺、莠去津两种组份同时进行定量分析。本方法中异丙草胺和莠去津变异系数分别为 0 .2 9%和 0 .5 8% ,平均回收率为 99.95 %和 10 0 .13% ,线性相关系数皆约为 0 .9999。     

Influence of mixing performance on polymerization of acrylamide in capillary microreactors

Nonliving free radical polymerization of acrylamide was chosen as a model reaction to investigate the effect of mixing performance on the polymerization in capillary microreactors. The polymerization rate was enhanced by increasing the volumetric flow rate and the reaction temperature at a constant residence time. However, higher temperatures led to lower Mn and larger PDI. The reaction mixture viscosity increased significantly during the polymerization. Both diffusion and dispersion coefficients were calculated to evaluate the mixing performance in microreactors. The capillary microreactor with a larger inner diameter led to higher monomer conversions, lower Mn and larger PDI compared to the capillary microreactor with a smaller inner diameter, which could be explained through a heat balance analysis for the polymerization and the dispersion effect. Moreover, it was found that the addition of a pre‐mixing stage minimized the effect of insufficient mixing between the initiators and the monomers on the polymerization. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1828–1840, 2018     

Effects of capillary condensation on adsorption and thermal desorption dynamics of water in zeolite 13X and layered beds

The effects of capillary condensation on the adsorption and thermal desorption dynamics of water in zeolite 13X beds and layered beds with zeolite 13X/silica gel or zeolite 13X/alumina were experimentally and theoretically studied. As the equilibrium isotherm of water on zeolite 13X pellet was found to be most favorable at a low relative humidity and indicated capillary condensation at a high relative humidity, it was possible to construct a non-isothermal model that included capillary condensation and that could successfully predict plateaus of temperature and concentration profiles in thermal regeneration. In adsorption breakthrough, by using a feed in the capillary condensation range of the isotherm on zeolite 13X, the breakthrough curve showed a shock wave in the low concentration and a proportionate pattern in the high concentration. In thermal desorption breakthrough, the desorbed water at the upper part of the bed was re-adsorbed at the lower part of the bed, and that re-adsorption mainly occurred in the capillary condensation range of the isotherm. Therefore, even though an adsorption was performed at a feed in the favorable range of the isotherm, and could be well predicted with type I isotherm, its desorption dynamics should be predicted by using the isotherm model with its consideration of capillary condensation. The layered bed with silica gel or alumina did not have any advantage over the zeolite 13X bed with respect to adsorption breakthrough performance. However, compared to the zeolite 13X bed, the complete regeneration time in the layered bed was drastically shortened due to a greater variation of the amount of equilibrium adsorption of water under temperature on both silica gel and alumina. In addition, since an increase in temperature led to a greater decrease of the amount of equilibrium adsorption of water on silica gel than on alumina, a layered bed with silica gel obviously could be regenerated more efficiently than a layered bed with alumina.     

宽孔弹性石英毛细管柱气相色谱分析高烷基丙烯酸酯

宽孔弹性石英毛细管往被成功地用于丙烯酸十六、十八酯的分析,文章详述了柱子的选择及定量程序。本方法具有简单、准确和新颖的特点。     

毛细管气相色谱法定量分析氟硅唑

采用HP-5石英毛细管色谱柱和FID检测器,以邻苯二甲酸二辛酯为内标物,在适宜的色谱条件下对40％氟硅唑乳油进行定量分析。色谱条件为柱箱采用程序升温,180℃保持0．5min,以25℃／min速率升至240℃,保持4min;进样口温度250℃。检测器温度250℃,气体流速为载气（N2）3ml／min,燃气（H2）30ml／min,助燃气（Air）300ml／min,分流比60：1．本方法的变异系数、平均回收率、标准偏差分别为0．16％、99．70％、0．064％,线性相关系数为0．9999。     

Wall coating behavior of catalyst slurries in non-porous ceramic microstructures

We report the use of the gas-displacement technique to generate wall coatings of catalyst slurries in fused silica capillaries, as well as ceramic microreactors. The non-porous and glassy surfaces make it difficult to prepare adherent coatings within ceramic structures. In the fused silica capillaries, we were able to show adherent catalyst coats up to thick and found that the maximum fraction coated decreased as the capillary diameter decreased. We developed a model for the various diameters showing the relationship of the fraction coated versus the capillary number, Ca. It was determined that the coating behavior was controlled by the coupled effects of the fluid rheology and the dramatic increase in the Reynold's number as the diameters decreased. For the ceramic microreactor, we determined that the coatings were adherent and tests showed the wall-coated catalyst in these structures to be catalytically active for the steam reforming of methanol.