Adsorption-Desorption Characteristics of Water Vapor on Functional Cattle Bone-Originated Apatites Powders with Mesopores

Microcrystals of cattle bone-originated apatites (r-HAp) were prepared by the dissolution-precipitation and freeze-drying processes. The r-HAp particles obtained gave 128 m 2 ;g m 1 specific surface area and 0.376 cm 3 ;g m 1 total pore volume and strong basic surface with mesopores. All the adsorption isotherms of water vapor at 288-308 K for the r-HAp powders obeyed IV-type in a classification of the BDDT. In the repeated adsorption-desorption operations, an adsorption hysteresis resulting from mesopores was recognized. The amounts of water vapor adsorbed obtained in the first adsorption operation were larger than those in the second adsorption operation, indicating that some portion of water vapor adsorbed to be irreversible adsorption. The water vapor-adsorption heats for the r-HAp were 45-60 kJ;mol m 1 , whose values were higher than natural diatomite. The amounts of water vapor adsorbed for the r-HAp were larger than those for the adsorbents, such as natural diatomite, aerosol silica, and activated carbon, at the relative partial pressures of 0-0.7.     

Silica particles encapsulated poly(styrene-divinylbenzene) monolithic stationary phases for micro-high performance liquid chromatography

In the paper we demonstrate a new approach for the preparation and application of continuous silica bed columns that involve encapsulation (entrapment) of functionalized silica microparticles, which can be used as packing material in micro high performance liquid chromatography (micro-HPLC) and capillary electrochromatography (CEC). Like traditional packed columns, these capillaries possess characterized silica particles that offer high phase ratio and narrow pore size distribution leading to high retention and separation efficiency, respectively. More importantly, immobilization of the microparticles stabilizes the separation bed and eliminates the need for retaining frits. The developed capillary columns were fabricated in exactly the same way as a packed capillary column (slurry packing) but with an additional entrapment step. This immobilization of the packed bed was achieved by in situ polymerization of styrene and divinylbenzene in presence of decanol as a porogen and azobisisobutyronitrile as thermal initiator. Silica particles with different particle sizes and pore sizes ranging from 60 to 4000 A were studied. In addition different modified silica was used, including C-18 reversed phase, anion exchange and chiral stationary phases. Efficient separation of polyphenolic compounds, peptides, proteins and even DNA mutation were achieved using the developed technique depending on the properties of the silica particles used (particles pore size). For example, using 3 microm ProntoSIL C-18 particles with 300 A pore size, separation efficiencies in the range of 120,000-200,000 plates/m were obtained for protein separation, in a 6 cm x 200 microm i.d. capillary column. Using encapsulated silica C-18 with 1000 A pore size, separation of DNA homo and hetero duplexes were achieved under denaturing HPLC conditions for mutation detection. In addition, nucleotides were separated using anion exchange material encapsulated with poly(styrene-divinylbenzene) (PS/DVB), which indicated that the chromatographic properties of the silica packing material were still active after polymerization. The prepared capillary columns were found to be stable and could easily be operated continuously up to a pressure of 350 bar without column damage and capillary can be cut to any desired length.     

Synthesis of Monodisperse Poly（glycidylmethacrylate-co-ethylene dimethacrylate） Beads and Their Application in Separation of Biopolymers

Introduction Since 19541 the polymeric separation media has attracted much attention due to their chemical stability over the entire pH range. The rigid, highly cross-linked styrene copolymers were first used for chromatography by Moore.2 The macroporous copolymers currently available are not only chemically stable but also more resistant to mechanical forces prevailing in a column and therefore are comparable to the traditional packings based on silica gel. Most polymer separation media are …     

Preparation and characterisation of poly(high internal phase emulsion) methacrylate monoliths and their application as separation media

Poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) monolithic supports were prepared by radical polymerisation of the continuous phase of water in oil high internal phase emulsions. Morphology of monolithic materials was studied by scanning electron microscopy and mercury intrusion porosimetry. The ratio of phase volume and the degree of crosslinking influenced the void size and pore size distribution of resulting polymers. Void sizes between 1 and 10 microm were observed and average pore sizes around 100 nm. Polymers with 60, 75, 80 and 90% pore volume were prepared and even samples with highest pore volume showed good mechanical stability. They were modified to bear weak-anion exchange groups and tested on the separation of standard protein mixture containing myoglobin, conalbumine and trypsin inhibitor. Good separation was obtained in a very short time similar to the separation obtained by commercial methacrylate monoliths. However, higher dispersion was observed. Bovine serum albumin dynamic binding capacity for monolith with 90% porosity was close to 9 mg/ml.     

A chromatographic comparison of the pore structure of zirconia high performance liquid chromatographic materials made by the polymerization induced colloidal aggregation and the Oil Emulsion methods

Summary The pore structures of zirconium oxide particles prepared by two different methods (PICA and Oil Emulsion processes) are compared. Nitrogen sorptometry and size exclusion chromatography are used to characterize the two different types of particles. Significant and unexpected differences were found in the accessible pore volumes and the bed packing densities of the two materials. The PICA material was found to have a higher totally included and totally excluded volume than would be normally expected. The chromatographic method provides results which are more useful for the application of these materials to separation sciences.     

Siliceous mesocellular foam for high-performance liquid chromatography: Effect of morphology and pore structure

Spherical siliceous mesocellular foam (MCF) particles with an average particle size of 4.8 μm have been successfully prepared. These spherical particles were tailored in pore sizes and surface areas. They were functionalized with C₈ or C₁₈ groups, and applied towards reversed phase high-performance liquid chromatography (HPLC) column separations. Their high surface areas gave rise to very good retention characteristics, as illustrated in the separation of a series of alkylbenzene solutes with increasing chain length. The highly interconnected porous structure and ultralarge pore size of MCF allowed the columns to be used at high flow rates without much loss in column efficiency. The column efficiency and peak symmetry were further improved by eliminating the micropores of the stationary phase. The reversed phase column packed with C₁₈-modified spherical MCF particles provided for excellent separation of different deoxynucleosides, illustrating the broad applicability of these materials due to their controlled pore size.     

Preparation of hydrophobic interaction chromatographic packings based on monodisperse poly(glycidylmethacrylate-co-ethylenedimethacrylate) beads and their application

The monodisperse, poly(glycidylmethacrylate-co-ethylenedimethacrylate) beads with macroporous in the range of 8.0-12.0 microm were prepared by a single-step swelling and polymerization method. The seed particles prepared by dispersion polymerization exhibited good absorption of the monomer phase. The pore size distribution of the beads was evaluated by gel permeation chromatography and mercury instrusion method. Based on this media, a hydrophobic interaction chromatographic (HIC) stationary phase for HPLC was synthesized by a new chemically modified method. The prepared resin has advantages for biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery and good resolution for proteins. The dynamic protein loading capacity of the synthesized HIC packings was 40.0 mg/ml. Six proteins were fast separated in less than 8.0 min using the synthesized HIC stationary phase. The HIC resin was firstly used for the purification and simultaneous renaturation of recombinant human interferon-gamma (rhIFN-gamma) in the extract solution containing 7.0 mol/l guanidine hydrochloride with only one step. The purity and specific bioactivity of the purified of rhIFN-gamma was found more than 95% and 1.3 x 10(8) IU/mg, respectively.     

基于硅胶整体材料研磨颗粒的多功能聚乙二醇键合固定相的制备及其在高效液相色谱多模式分离中的应用

研究通过对溶胶-凝胶法制备的硅胶整体材料进行研磨、浮选、假晶相转换和水热处理，最终获得了粒径为2~5 μm、孔径为20~60 nm的硅胶颗粒。利用部分含氟的阴离子表面活性剂Capstone FS-66和常用的阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）组成的双胶束模板体系对硅胶基质进行假晶相转换处理；再采用碳酸钠溶液水热处理的方式，进一步扩大孔径。用扫描电镜（SEM）和N₂吸附-解吸等温线测量对扩孔处理前后的硅胶整体材料研磨颗粒进行表征，结果清楚地显示了处理前后的形貌变化和差异。随后将含有长链聚乙二醇（PEG）的硅烷键合到扩孔后的硅胶颗粒表面，分别利用元素分析、红外光谱以及热重分析对固定相进行表征，并对固定相进行色谱性能评价。对键合固定相的元素分析和热重分析数据进行分析表明，硅胶表面键合PEG的含量约为8%。研究揭示了利用假晶相转换法与碳酸钠溶液水热处理和长链PEG硅烷修饰的硅胶整体材料颗粒在尺寸排阻色谱分离蛋白质方面的良好分离效果。同时进一步的高效液相色谱评价结果表明，该键合固定相还可用于疏水作用色谱模式分离核糖核酸酶A和溶菌酶，以及可用于亲水作用色谱模式分离吡啶甲酸、左旋多巴、三聚氰胺和邻苯二酚等极性比较强的化合物。研究显示了PEG键合固定相具有多功能性，及其在多模式高效液相色谱分离中的应用潜力。     

Magnesium oxide microspheres as a packing material for the separation of basic compounds in normal-phase liquid chromatography

Uniform monodisperse magnesium oxide microspheres with a high surface area have been prepared by a facile seed-induced precipitation. By characterizing these particles with scanning electron microscopy and N(2) physisorption techniques, the results demonstrate that these magnesium oxide microspheres have an average particle diameter of 9.5 microm, a specific surface area of 211.7 m(2)g(-1), a total pore volume of 0.76 mL g(-1), and an average pore diameter of 143 A. The chromatographic properties of these microspheres have been investigated in normal-phase mode for the separation of various basic compounds including aniline, quinoline, and pyridine derivatives. In contrast to conventional silica, the magnesium oxide particles exhibit unique selectivity and retention property for the separation of the tested basic compounds, and these microspheres are promising as an alternative new packing material for high-performance liquid chromatography.     

亚微米中孔SBA-15 棒状固定相在毛细管电色谱分离中的应用(英文)

采用中孔SBA-15棒状硅胶颗粒填充毛细管柱用于毛细管电色谱(CEC)分离。这一亚微米材料直径为400 nm并具有沿相同方向伸展的高度有序、均一的圆柱形中孔。棒状的特殊形态使得填充柱的通透性良好,简化了尺寸微小的CEC柱的填充过程。修饰后的棒状SBA-15填充毛细管柱成功应用于反相和离子交换电色谱分离非极性和极性样品,获得了较高柱效(140000理论塔板/m)。流速3.2cm/min时获得最低理论塔板高度为7.1 mm。范迪米特曲线说明了SBA-15孔结构的传质阻力特征。分别以芳香酸、人参、天麻提取物为样品,对亚微米固定相毛细管电色谱柱加以评价。该固定相显示出了较高的分离能力,为纳米材料在色谱固定相中的应用提供了一个新的思路。     

原子转移自由基聚合法制备超大孔聚合物微球

以甲基丙烯酸缩水甘油酯为单体(GMA)、乙二醇二甲基丙烯酸酯(EDMA)为交联剂,采用原子转移自由基聚合法(ATRP)制备了PGMA-EDMA大孔聚合物微球,采用傅里叶变换红外光谱、扫描电子显微镜及压汞法对PGMA-EDMA微球进行了表征.研究结果表明,原子转移自由基聚合法制备的PGMA-EDMA微球的孔径尺寸及比表面积均大于普通自由基聚合法(CFRP)制备的PGMA-EDMA;ATRP法制备的PGMAEDMA微球的颗粒尺寸(100~400 nm)明显小于CFRP法制备的PGMA-EDMA微球的颗粒尺寸(1000 nm).PGMA-EDMA(ATRP)的微球粒径尺寸分布优于PGMA-EDMA(CFRP).因此PGMA-EDMA(APRP)微球在快速蛋白分离纯化方面有潜在的应用前景.     

The sepiolite membrane for ultrafiltration

Novel inorganic membranes were prepared from clay (sepiolite) suspensions, which were formed by dispersing clay particles in water either by applying ultrasonic wave or by magnetic stirring. Films can be formed easily from such suspensions due to fibrous nature of sepiolite. Thus, this offers a method much simpler than the conventional sol–gel method. The membranes were further tested for ultrafiltration of polyethylene glycol and polyethylene oxide solutes of different molecular weights. It was found that the correlation between the separation and the Einstein–Stokes radius of solute fits the log-normal distribution very well. The mean pore size of 23–26 nm and the standard deviation of 1.91–2.04 were obtained from the above correlation. It was also found that the mean pore size and the pore size distribution did not depend very much on the membrane preparation method.     

A new emulsion method to synthesize well-defined mesoporous particles

A new emulsion method for preparing ordered mesoporous materials with polymer PEG as the swelling agent has been explored in the present work. The synthesis conditions including the chain length and the PEG concentration, the duration of aging, the kind of emulsion, and the time when the swelling agents were added to the reaction system are discussed. The results show that with the advantage of the emulsion method, the nucleation and growth were controlled very well. The nicely spherical particles produced by the emulsion method were more uniform and less prone to agglomerate than those produced through the hydrothermal method. When different MW PEG were added as swelling agents, the pore size changed little: it was centered around 4 nm and had a narrow distribution. When different concentrations of PEG were applied, BET surface area, pore size, and pore volume changed. To summarize, in the formation of mesoporous materials, polymers such as PEG can not only control the pore size from 3 to 70 nm through variation of concentration, but also regulate the structures and improve the morphology of particles by the chain length of polymers. By adjusting the time of addition of the swelling agents, a poroshell mesoporous material was prepared. This method is particularly important for those applications that strictly require particle uniformity, such as chromatography separation.     

Fabrication of poly(lactide‐co‐glycolide) scaffold embedded spatially with hydroxyapatite particles on pore walls for bone tissue engineering

Poly(lactide‐co‐glycolide) (PLGA) scaffolds embedded spatially with hydroxyapatite (HA) particles on the pore walls (PLGA/HA‐S) were fabricated by using HA‐coated paraffin spheres as porogens, which were prepared by Pickering emulsion. For comparisons, PLGA scaffolds loaded with same amount of HA particles (2%) in the matrix (PLGA/HA‐M) and pure PLGA scaffolds were prepared by using pure paraffin spheres as porogens. Although the three types of scaffolds had same pore size (450–600 µm) and similar porosity (90%–93%), the PLGA/HA‐S showed the highest compression modulus. The embedment of the HA particles on the pore walls endow the PLGA/HA‐S scaffold with a stronger ability of protein adsorption and mineralization as well as a larger mechanical strength against compression. In vitro culture of rat bone marrow stem cells revealed that cell morphology and proliferation ability were similar on all the scaffolds. However, the alkaline phosphatase activity was significantly improved for the cells cultured on the PLGA/HA‐S scaffolds. Therefore, the method for fabricating scaffolds with spatially embedded nanoparticles provides a new way to obtain the bioactive scaffolds for tissue engineering. Copyright © 2011 John Wiley & Sons, Ltd.     

CEC separation of ofloxacin enantiomers using imprinted microparticles prepared in molecular crowding conditions

Molecular crowding is a new concept to obtain molecularly imprinted polymers (MIPs) with greater capacity and selectivity, which could shift the equilibrium of a print molecule reacting with functional monomers in the direction of complex formation side. In this work, molecular crowding agent was first applied to the preparation of MIPs microparticles by precipitation polymerization. A new system of molecular crowding surrounding was developed, composed of polystyrene and tetrahydrofuran, in the presence of the template (S)-ofloxacin. Partial filling capillary electrochromatography (CEC) was utilized to evaluate imprinting effect of the resulting microparticles by chiral separations of ofloxacin. Some important parameters in the preparation, i.e. template to monomer ratio, influence of cross-linking monomers and functional monomer composition on the CEC separation of MIP microparticles were investigated. Baseline separation of ofloxacin (R(s) =1.53) was obtained under optimized conditions and the highest theory plate of the later eluent (S)-ofloxacin was 5400. The textural and morphological parameters for imprinted particles, such as Brunauer-Emmett-Teller surface areas, pore volumes and pore size distributions have also been determined. Compared to the MIP microparticle prepared by conventional precipitation polymerization, the (S)-ofloxacin-imprinted particles formed under molecular crowding conditions showed higher selectivity (α=1.09) and separation efficiency (<25 min) in the CEC mode.     

Monodisperse porous polymer particles: Formation of the porous structure

Monodisperse porous styrene-divinylbenzene copolymer particles were prepared via seeded emulsion polymerization using a mixture of linear polymer (polystyrene seed) and non-solvent as inert diluent. Experimental evidence was presented to describe the mechanism of formation of porous polymer particles during the copolymerization and solvent extraction stages, in which porosity was a consequence of phase separation in the presence of diluents. Pore structure formation was investigated by changes in copolymerization kinetics, gel content, crosslinking density, particle morphology, surface area, pore volume, and pore size distribution. The process of copolymerization was presented, based on the concepts of production, agglomeration, and fixation of the interior gel microspheres of polymer particles. A portion of linear polymer used as diluent was found to participate in the network structure while the porous matrix was built-up. The influence of the removal of the linear polymer from the matrix pores during the solvent extraction process on the porous structure was also discussed.     

Evaluation of silica from different vendors as the solid support of anion‐exchange chiral stationary phases by means of preferential sorption and liquid chromatography

Chromatographic performance of a chiral stationary phase is significantly influenced by the employed solid support. Properties of the most commonly used support, silica particles, such as size and size distribution, and pore size are of utmost importance for both superficially porous particles and fully porous particles. In this work, we have focused on evaluation of fully porous particles from three different vendors as solid supports for a brush‐type chiral stationary phase based on 9‐O‐tert‐butylcarbamoyl quinidine. We have prepared corresponding stationary phases under identical experimental conditions and determined the parameters of the modified silica by physisorption measurements and scanning electron microscopy. Enantiorecognition properties of the chiral stationary phases have been studied using preferential sorption experiments. The same material was slurry‐packed into chromatographic columns and the chromatographic properties have been evaluated in liquid chromatography. We show that preferential sorption can provide valuable information about the influence of the pore size and total pore volume on the interaction of analytes of different size with the chirally‐modified silica surface. The data can be used to understand differences observed in chromatographic evaluation of the chiral stationary phases. The combination of preferential sorption and liquid chromatography separation can provide detailed information on new chiral stationary phases.     

Synthesis of magnetic chelator for high-capacity immobilized metal affinity adsorption of protein by cerium initiated graft polymerization

A novel magnetic chelator with high adsorption capacity of protein by immobilized metal affinity adsorption was prepared by cerium (IV) initiated graft polymerization of tentacle-type polymer chains with iminodiacetic acid (IDA) chelating group on magnetic particles with hydroxyl groups. The micron-sized magnetic poly(vinyl acetate-divinylbenzene) (PVAc-DVB) particles were prepared by a modified suspension polymerization in the presence of oleic acid-coated magnetite nanoparticles and subsequently modified by ester exchange reaction to introduce functional hydroxyl groups. Bovine hemoglobin (BHb) was selected as a model protein to investigate the adsorption capacity of these magnetic particles. The magnetic particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), superconducting quantum interference device (SQUID) magnetometry, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray diffraction (XRD). The results showed that the magnetic particles had an average size of 5 microm and superparamagnetism with saturation magnetization of 20.0 emu/g at room temperature. The protein adsorption indicated that the graft polymerization of tentacle type polymer chains on the magnetic particles could produce magnetic adsorbents with high adsorption capacity (1428.21 mg/g) and low nonspecific adsorption of protein. The magnetic particles with grafted tentacle polymer chains have potential application in large-scale affinity separation of proteins.     

Preparation and Chromatographic Features of Fibrous Core–Shell HPLC Packing Material

In this study, fibrous core–shell silica particles were successfully synthesized via a one-step oil–water biphase stratification coating strategy. The core–shell silica particles were composed of 3-µm non-pore silica cores and thin shells (50–100 nm), which have radial-like direct channels and a large pore size (19.89 nm). The fibrous core–shell silica particles were further modified by n-octadecyltrichlorosilane and used as stationary-phase media in high-performance liquid chromatography (HPLC). The chromatographic properties of the particles were systematically studied in small-molecule and protein separation processes. The results showed that the back pressure was as low as 8.5 MPa under the 1.0-mL min^?1 flow velocity. Furthermore, fibrous core–shell silica particles with an 80-nm shell were used for separating seven small molecules within 10 min and six proteins within 6 min. This work demonstrates that the fibrous core–shell silica particles could be used as an HPLC stationary phase with good performance and low back pressure, and that they have great potential for application to HPLC separation in the future.     

Reversed-phase liquid chromatography of proteins and peptides using multimodal copolymer-encapsulated silica

Multimodal copolymer-encapsulated particles for liquid chromatography were prepared by bonding 1-octadecene and unsaturated carboxylic acids on silica particles (5 microm diameter, 300 A pores) for liquid chromatography of proteins. These multimodal copolymer-encapsulated particles can provide both hydrophobic and hydrogen bonding interactions with polar compounds. The chromatographic performance of these multimodal copolymer-encapsulated particles for peptide and protein separations was evaluated under reversed-phase conditions. Compared with typical C8-bonded silica, polymer-encapsulated particles were more stable in acidic mobile phases and provided better recoveries, especially for large proteins (Mr>0.5 x 10(6)). Totally hydrophobic polymer-encapsulated particles were found to produce broad peaks for proteins, and significant improvements were observed by introducing hydrophilic groups (-COOH) onto the polymer-encapsulated surface to form a multimodal phase. For the reversed-phase liquid chromatography of peptides and proteins, improved selectivity and increased solute retention were found using the multimodal polymer-encapsulated particles. More peaks were resolved for the separation of complex peptide mixtures such as protein digests using the multimodal polymer-encapsulated particles as compared to totally hydrophobic polymer-encapsulated particles.