锆基色谱填料的制备方法和物理化学性质

氧化锆基质色谱填料适合于碱性物质,特别是生物大分子的分离,因而具有良好的应用前景。它的制备方法对其物理化学性质有很大的影响,从而影响填料的色谱性能。该文对氧化锆微球的制备方法及其物理化学性质进行了综述。分析表明,目前氧化锆基质色谱填料的制备方法存在着难以克服的缺点,要制备理想的锆基色谱填料需要新的思路。     

Separation of enantiomers on bovine serum albumin coated zirconia in reversed-phase liquid chromatography

Summary Zirconia is known to be one of the best materials for the chromatographic support due to its excellent chemical, thermal and mechanical stability. In this work we report preparation and use of bovine serum albumin (BSA)-immobilized zirconia as a chiral stationary phase for separation of some enantiomers in reversed-phase liquid chromatography. The BSA-zirconia showed good enantioselectivity for some of the enantiomers studied and could be used for RPLC separations in mobile phases of alkaline pH.     

Evaluation of titania as an ion-exchanger and as a ligand-exchanger in HPLC

Summary The chromatographic properties of titania have been compared with those of zirconia and alumina, by comparison of their relative Lewis acidities whenp-substituted benzoic acids were chromatographed with aqueous mobile phases. The retention behavior ofp-substituted benzoic acids on titania was found to be similar to that on zirconia; the slopes of plots of retention factors against solute pK _a were approximately parallel for all pH values and the slopes obtained were similar to the average slope for zirconia. The shapes of solute peaks on titania were more symmetrical than on alumina and zirconia. The effect of calcination temperature on the chromatographic properties of titania was examined by use of titania prepared at different temperatures. The results obtained clearly showed that the preparation temperature affected the chromatographic properties of titania. It seemed, for example, that titania dried at 40°C behaved as a cation-exchanger, titania heated at 200°C behaved as an amphoteric exchanger, and titania calcined at 600°C behaved as an anion-exchanger in the pH range 4.1–6.5 It was found that the control of the preparation temperature enabled us to make effective use of titania.     

Separation of racemic 2,4-dinitrophenyl amino acids on 9-O-(phenyloxycarbonyl)quinine-bonded carbon-clad zirconia in reversed-phase liquid chromatography

Zirconia is known to be one of the best materials for the chromatographic support due to its excellent chemical, thermal, and mechanical stability. In this work, we report preparation and use of 9-O-(phenyloxycarbonyl)quinine-bonded carbon-clad zirconia (QNCZ) as a chiral stationary phase (CSP) for separation of N-(2,4-dinitrophenyl) (DNP)-amino acids (AAs) enantiomers in reversed-phase liquid chromatography. Retention and enantioselectivity of the QNCZ CSP were compared with those of quinine 3-triethoxysilylpropylcarbamate-coated zirconia (QNZ) and quinine 3-triethoxysilylpropylcarbamate-bonded silica (QNS). The QNCZ CSP showed in general the better enantioselectivity for most of the amino acids studied.     

磷霉素改性氧化锆固定相色谱性能研究

本文利用磷霉素与氧化锆表面的强Ｌｅｗｉｓ酸碱作用,分别采用静态和动态两种途径以磷霉素对自制ＺｒＯ２固定相进行改性,考察了改性前后固定相色谱性能的变化。通过磷霉素改性,能够较好地覆盖氧化锆表面存在的Ｌｗｅｉｓ酸活性中心点,从而减少对酸性化合物的不可逆吸附及拖尾现象。磷霉素动态改性氧化锆表现出一定的反相色谱性能,静态改性氧化锆则表现出较强的极性。     

Preparation and Evaluation of Calix[8]arene Bonded Silica Stationary Phase for High Performance Liquid Chromatography

In recent years, calix[n]arenes (n=4,5,6,7,8) as stationary phase have been introduced into the field of chromatography. In our previous works, we have synthesized, characterized and evaluated two different silica-bonded calix[n]arenes (n=4,6) stationary phase, on which the chromatographic behavior of PAHs, positional isomers,nucleosides and bases was investigated. In this paper we report the preparation of calix[8]arene bonded silica stationary phase, and characterization of its structure and chromatographic behavior.     

Chromatographic characterization of a phosphate-modified zirconia support for bio-chromatographic applications.

A phosphate-modified zirconia was investigated for its potential use as a high-performance inorganic cation-exchange support for the separation of proteins. This phosphate modification effectively blocks the sites responsible for the strong interactions of certain Lewis bases with the zirconia surface. It provides a more "bio-compatible" stationary phase, resulting in high recoveries for proteins and enzymes and retention of their enzymatic activity. The stability, loading capacity, selectivity, efficiency and separation mechanism on the phosphate-modified zirconia are reported. These studies have shown that phosphate-modified zirconia is a useful high-performance ion-exchange support for the separation of cationic proteins and for blocking the sites responsible for the high affinity of zirconia towards certain anions. This makes the phosphate modification interesting in its own right and as an intermediate stage for the development of other zirconia-based chromatographic supports.     

Preparation and Evaluation of Octadecyl-Bonded ZrO2/SiO2

ZrO₂/SiO₂ particles, which were prepared by a layer-by-layer self-assemble technique and consist of micrometer-sized silica spheres as cores and nanometer-sized zirconia particles as surface coatings, have a higher surface area and pore volume than other zirconia supports have. Further more it is more stable than silica is. In this paper we made a reversed-phase support by bonding octadecyltrichlorosilane on ZrO₂/SiO₂ particles, it had a comparable high carbon amount of 9.62% and good chemical stability being stable up to pH 11. The chromatographic behavior showed that the support acted as a true reversed chromatographic stationary phase and had a hydrophobic selectivity. Basic and aromatic compounds are well separated and the peaks are symmetrical.     

Cellulose dimethylphenylcarbamate-bonded carbon-clad zirconia for chiral separation in high performance liquid chromatography.

Porous zirconia particles are very robust material and have received considerable attention as a stationary phase support for HPLC. We prepared cellulose dimethylphenylcarbamate-bonded carbon-clad zirconia (CDMPCCZ) as a chiral stationary phase (CSP) for separation of enantiomers of a set of 14 racemic compounds in normal phase (NP) and reversed-phase (RP) liquid chromatography. Retention and enantioselectivity on CDMPCCZ were compared to those on CDMPC-coated zirconia (CDMPCZ) to see how the change in immobilization method of the chiral selector affects the retention and chiral selectivity. In NPLC, retention was longer and the number of resolved racemates was smaller on CDMPCCZ than on CDMPCZ. However, chiral selectivity factors for some resolved racemates were better on CDMPCCZ than on CDMPCZ. The longer retention on CDMPCCZ is likely due to strong, non-chiral discriminating interactions with the carbon layer on CDMPCZ. In RPLC only two racemates were resolved on CDMPCCZ, but retention times were shorter than, and resolutions were comparable to, those in NPLC, indicating a potential for improving chromatographic performance of the CDMPCCZ column in RPLC with optimized column preparation and separation conditions.     

Synthesis and Characterization of Aluminum Doped Nano-ZrO2 by Surfactant-assisted Route

Recently, more and more interest has been focused on zirconia and its chara- cteristics. In this paper, aluminum can be successfully incorporated into nano-ZrO2 via a cationic surfactant assisted route in the earlier preparation procedure. XRD, TEM, EDS, Uv-vis and N2 adsorption-desorption analysis methods were adopted for the characterization of prepared samples. The results show that aluminum has been homogeneously incorporated into nano-ZrO2. The prepared aluminum-doped samples show a distinctive blue shift in the Uv-vis spectra compared to normal nano-ZrO2. The distinctive increase of thermal stability and a mesoporous structure were observed.     

Separation of racemic 2,4-dinitrophenyl amino acids on zirconia-immobilized quinine carbamate in reversed-phase liquid chromatography

Zirconia is known to be one of the best chromatographic support materials due to its excellent chemical, thermal, and mechanical stability. A quinine carbamate-coated zirconia was prepared as a chiral stationary phase for separation of enantiomers of DNP-amino acids in reversed-phase liquid chromatography. Retention and enantioselectivity of this phase were compared to those for quinine carbamate bonded onto silica. Most amino acids studied were separated on the quinine carbamate-zirconia CSP although retention was longer and chiral selectivity was somewhat lower than on the corresponding silica CSP. Increased retention and decreased selectivity are probably due to strong non-enantioselective Lewis acid-base interactions between the amino acid molecule and the residual Lewis acid sites on the zirconia surface.     

表层二氧化锆/硅基－CDMPC手性固定相的制备及联苯双酯类保肝药的直接拆分

用分子自组装的方法制备了表层纳米氧化锆包覆多孔微米硅球，得到的氧化锆 /硅胶微球用作高效液相色谱担体，本方法制备的担体具有氧化锆的表面特性并保 持了硅胶的颗粒均匀、表面积大、渗透性好的优点，可以制备大涂敷量的手性固定 相，以增加固定相的手性识别能力，以涂敷量为20%的纤维素－三（3，5-二甲基苯 基氨基甲酸酯）－氧化锆/硅胶手性固定相（CDMPC-coated ZrO_2/SiO_2）上，对 联苯双酯类保肝药物进行直接拆分，考察了流动相极性、第二种极性改性剂对样品 保留和拆分的影响；并对手性拆分机理进行了阐述，结果表明：CDMPC- ZrO_2/SiO_2手性固定相比CDMPC-ZrO_2具有更好的手性拆分能力。     

Enantioseparation on cellulose dimethylphenylcarbamate-modified zirconia monolithic columns by reversed-phase capillary electrochromatography

This work reports the preparation of monolithic zirconia chiral columns for separation of enantiomeric compounds by capillary electrochromatography (CEC). Using sol–gel technology, a porous monolith having interconnected globular-like structure with through-pores is synthesized in the capillary column as a first step in the synthesis of monolithic zirconia chiral capillary columns. In the second step, the surface of the monolith is modified by coating with cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) as the chiral stationary phase to obtain a chiral column (CDMPCZM). The process of the preparation of the zirconia monolithic capillary column was investigated by varying the concentrations of the components of the sol solution including polyethylene glycol, water and acetic acid. CDMPCZM is mechanically stable and no bubble formation was detected with the applied current of up to 30 μA. The enantioseparation behavior of the CDMPCZM columns was investigated by separating a set of 10 representative chiral compounds by varying the applied voltage and pH and organic composition of the aqueous organic mobile phases.     

表层纳米氧化锆包覆硅球色谱载体的制备和表征

硅胶是目前应用最为广泛的色谱载体. 硅胶的比表面积及孔体积大, 渗透性好, 孔结构适宜于色谱分离, 但在pH＜2及pH＞8条件下不稳定, 对碱性化合物, 尤其是对生物样品产生不可逆吸附. 氧化锆化学性质非常稳定[1], 适宜碱性样品尤其是生物大分子的分离; 但是其比表面积和孔体积小[2～5], 孔结构对色谱分离不利[6], 可涂敷的固定相量较小, 渗透性差. 本文采用分子自组装方法[7～9]在微米硅球表面包覆多层纳米氧化锆制备了较为理想的色谱载体.     

Retention and selectivity tests of silica-based and metal-oxide bonded stationary phases for RP-HPLC

Chromatographic properties of silica-, zirconia- and alumina-based columns with octadecyl-, polyethylene glycol- and pentafluorophenylpropyl-bonded stationary phases were tested. Selectivities of nine columns for LC were characterized using chromatographic methods including Walters, Engelhardt, Tanaka and Galushko hydrophobicity and silanol activity tests, measurements of methylene selectivity in various aqueous-methanol and aqueous-acetonitrile mobile phases and of gradient lipophilic capacity as a measure of the effect of the sample hydrophobicity on gradient-elution separations. A semi-empirical interaction indices model, assuming a predominant role of the solvophobic interactions of test compounds with different polarities, was compared with the linear free energy relationships approach taking into account selective polar interactions. The interaction indices model was applied to both non-polar stationary phases bonded on silica, alumina and zirconia supports, and to the non-modified adsorbents in the normal-phase LC. The retention data of isomeric naphthalene disulfonic acids were used to compare the attractive and repulsive ionic interactions of the columns in purely aqueous mobile phases. The results of the hydrophobicity and polarity tests were consistent, and allowed column characterization and classification. Silanol activity was important with octadecyl silica columns, but was relatively insignificant with bonded polyethylene glycol and pentafluorophenylpropyl phases on silica gel support. Polar interactions with the alumina and zirconia support materials significantly affect the retention.     

A comparative study of the surface structure, acidity, and catalytic performance of tungstated zirconia prepared from crystalline zirconia or amorphous zirconium oxyhydroxide

Tungstated zirconias prepared from W deposition on zirconium oxyhydroxide are reportedly active for alkane isomerization, whereas solids synthesized by impregnation of zirconia are inactive. The origin of the differences between the two preparations is not fully understood. The present paper examines the influence of W surface density and the nature of the support on the surface structure, development of the acidity, and catalytic performance of WO(x)()/ ZrO(2) catalysts. Two series of catalysts containing W surface densities up to 5.2 at. W/nm(2) were prepared by pore volume impregnation of two different supports: zirconium oxyhydroxide and predominantly tetragonal zirconia (65% tetragonal, 35% monoclinic). The texture and structure of the catalysts were investigated by BET measurements, X-ray diffraction, Raman and infrared spectroscopy. The catalytic activity was tested for 2-propanol dehydration and n-hexane isomerization. For catalysts obtained by impregnation of Zr oxyhydroxide, Raman results showed that W was present as a surface phase. Infrared spectra indicated an increase in the degree of polymerization of W species with increasing W surface density. The development of the acidity was monitored by lutidine adsorption and desorption at 523 K, followed by infrared spectroscopy. The results indicated the presence of a threshold of W surface density at 1.3 at. W/ nm(2) for the detection of these acid sites, followed by a progressive increase in their abundance with increasing W surface density. The development of Br?nsted acidity correlated with the evolution of the infrared bands attributed to "extensively" polymerized W species. A direct relationship was observed between the abundance of Br?nsted acid sites and the catalytic activity for 2-propanol dehydration. For n-hexane isomerization, compared to 2-propanol dehydration, a higher threshold of W surface densities (3.4 at. W/ nm(2)) for the development of activity was observed. The difference was attributed to stronger Br?nsted acid sites required for n-hexane isomerization. The catalysts prepared by impregnation of zirconia exhibited comparable behavior. For a given W surface density, the crystalline composition of the support (tetragonal/monoclinic zirconia), the W surface structure, abundance of Br?nsted acid sites, and catalytic performance were similar. Thus, in an apparent variance with some of the results reported in the literature with respect to the influence of preparation methods, no significant effect of the initial form of the support (Zr oxyhydroxide versus predominantly tetragonal zirconia) was evidenced.     

Synthesis and characterization of new organometallic complexes bonded stationary phases for high-performance liquid chromatography

Summary The preparation, characterization and potential liquid chromatographic applications of various organometallic iron complexes silica stationary phases are presented. These new supports are synthesized by covalently linking ferrocene, as well as some of its cationic derivatives, to appropriately derivatized silica support matrices. These columns exhibit moderate to high selectivity towards the separation of polycyclic aromatic hydrocarbons (PAHs). A charge transfer retention mechanism has been proposed. A comparison with a reference stationary phase, 3,5-dinitrobenzamide (DNB), to quantify the acceptor power of the new stationary bonded phases, is also reported. Finally, the effect of varying the derivatives of the bonded metallocene on PAHs retention is discussed.     

Oxidative dehydrogenation of propane on the VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/CeZrO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> supported catalyst

The oxidative dehydrogenation of propane on a supported vanadium catalyst was studied (the support was a complex oxide system consisting of a ceria–zirconia solid solution deposited on γ-Al₂O₃ (CeZrO/γ-Al₂O₃)). A comparative analysis of the properties of the support and the catalyst prepared on its basis was performed. The support and catalyst were characterized by the BET method, scanning electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. The catalytic properties of the catalyst and support were studied in propane oxidation at 450 and 500°C with pulse feeding of the reagent. The effect of propane on the support was found to improve the oxidative properties of the latter. This behavior of the support is related to the preparation procedure, which leads to the formation on its surface of the crystalline phase of the ceria–zirconia solid solution and amorphous ZrO₂ and Al₂O₃ phases and/or their solid solution. Similar processes occur with the catalyst support during the oxidative dehydrogenation, giving rise to additional active centers (CeVO₄).     

氧化锆填料的高效液相色谱性能评价

研究了采用溶胶－凝胶技术制备的４－６μｍ粒径氧化锆微球的晶体结构,比表面积,孔容,孔径分布及表面酸碱性,测得氧化锆以单斜相和四方相２种相存在。微球的比表面积为２１ｍ６２／ｇ;总孔容为０．１２８０ｃｍ＾３／Ｌ;平均孔直径为８．６ｎｍ。氧化锆的表面存在酸碱两性。分别以异丙醇／环己烷,二氧甲烷／环己烷及三氯甲烷／环己烷为流动相研究了苯酚衍生物,芳香烃衍生物及苯胺等碱性化合物的保留行为。