硅基寡聚砜型新型HPLC固定相的制备及其色谱性能评价

以硅小球为基质,γ-氨丙基三乙氧基硅烷,环硫乙烷和过氧乙酸为改性剂,制备了硅基寡聚砜型新型液相色谱固定相。在活化的硅小球表面引入氨基,制得氨基键合相,然后氨基键合相与环硫乙烷进行开环聚合反应,在氨基键合相表面引入巯基和硫醚基,最后用过氧乙酸将其分别氧化为磺酸基和砜基,制得磺酸乙基聚乙砜基胺丙基固定相。采用元素分析进行表征,通过S和N的摩尔比确定固定相表面胺基,砜基和磺酸基的比例。在不同条件下,分别选用碱性化合物、中等极性和弱极性化合物等13种溶质对该固定相的色谱性能进行评价,证明该固定相兼有疏水作用,亲水作用和静电作用。用于实际样品测定,该固定相呈现出良好的分离选择性和较广的应用范围。     

氮氧化硅反相色谱固定相材料的制备及色谱分离性能评价

硅胶是目前高效液相色谱(HPLC)固定相中应用最为广泛的基质材料,其流动相的最佳使用范围为pH 2～8。在高pH(pH＞8)的流动相条件下,流动相中的氢氧根会进攻硅胶基质表面残余的硅醇基,导致硅胶基质固定相骨架溶解。在前期的研究中,我们将高温氨气处理多孔硅胶微球得到的氮氧化硅材料用作HPLC固定相,氮氧化硅在高pH流动相条件下表现出了较硅胶更高的稳定性。本文利用元素分析对氮氧化硅材料的氮化程度及含氮量进行系统的表征,并考察了氮氧化硅材料在不同pH条件下的静态稳定性。利用十八烷基二甲基氯硅烷试剂对氮氧化硅材料表面进行疏水性修饰,并以元素分析和核磁共振波谱对表面键合氮氧化硅材料进行了表征。考察了不同碳链的烷基苯、酸性化合物、碱性化合物在疏水改性的C₁₈氮氧化硅反相色谱固定相上的色谱分离性能。进一步分别以酸、碱和中性化合物为分析对象,比较了C₁₈-SiON1050(10)与C₁₈-SiO₂色谱保留的差异。     

一种评价固定相表面硅羟基残余的新方法

常规的反相色谱柱评价方法未涉及固定相表面残余硅羟基活性的评价.本文以阿米替林的不对称度作为指标,发展了一种评价固定相表面残余硅羟基的新方法,并对十种不同品牌的反相色谱柱进行评价.基于评价结果,选取其中两支色谱柱对碱性抗茵药物进行色谱分离.结果表明,发展的评价方法能够很好地反映反相固定相的硅羟基残余情况,可以为选择色谱柱分离有机碱提供有价值的信息.     

1-萘甲膦酸改性氧化锆固定相的反相色谱性能研究

采用Lewis酸碱吸附改性方法制备了1-萘甲膦酸改性氧化锆色谱固定相,通过元素分析、漫反射红外光谱等对该固定相的表面性质进行了表征;以中性含π电子化合物作探针,考察了以甲醇/水为流动相、在13±3℃的柱温下固定相的色谱性能和分离机理;考察了该新型固定相的稳定性。结果表明,1-萘甲膦酸改性氧化锆固定相呈现出明显的反相色谱特征,对苯同系物、稠环芳烃和芳香族硝基化合物具有较好的分离选择性。     

聚苯乙烯包夹硅基高效液相色谱固定相的研究

用包夹聚合法制备出一种新型的聚苯乙烯包夹硅基高效液相色谱固定相并进行了固定相的表征。对色谱行为的研究表明此固定相在分离碱性、强极性溶质时有良好的分离性能,固定相在较高ｐＨ的洗脱液中有较好的稳定性。     

均相合成多重选择性的新型两亲性C22高效液相色谱固定相

为解决高效液相色谱（HPLC）固定相非均相合成中产物多变和重现性差等问题,该文采用均相合成新方法,制备了既含有二十二碳烷基（C22）、又嵌入脲（U）和/或酰胺（A）强极性基团的两种新型两亲性色谱固定相C22-A和C22-A/U。通过元素分析、核磁等手段,证实制备的两种新型固定相含有碳、氮元素,且碳氮元素比例符合理论值,表明酰胺和脲基极性基团成功键合到硅胶上。通过对多种样品进行色谱分离分析,对两种新型固定相的载体残余硅羟基屏蔽作用、疏水选择性、形状选择性和亲水性等多种性质进行了考察,证实两种新型固定相不但具备作为反相液相色谱（RPLC）的性能,同时也具备亲水相互作用色谱（HILIC）的性能。相较于C18固定相,C22-A和C22-A/U具有更好的形状选择性,双重嵌入的极性基团极大地降低了固定相硅羟基活性。将C22-A和C22-A/U两种固定相应用于几种碱性化合物、雌醇（酮）类化合物的分离,C22固定相在一定程度上解决了传统C18固定相上碱性化合物分离拖尾严重或保留不足的问题,成功实现了对雌醇（酮）类化合物的分离。     

纳米氧化锆沉积硅胶色谱固定相的制备及亲水作用色谱行为

采用液相沉积法(LPD)制备了纳米氧化锆沉积硅胶色谱固定相(ZrO₂/SiO₂), 并将其应用于亲水作用色谱分离中. 考察并比较了ZrO₂/SiO₂、 硅胶(SiO₂)和氧化锆(ZrO₂) 3种色谱固定相在不同有机调节剂比例、 不同pH值及不同盐浓度的流动相条件下的色谱行为. 结果表明, 制备的ZrO₂/SiO₂色谱柱不仅具有SiO₂色谱柱高柱效的优点, 表面沉积的纳米氧化锆还能有效屏蔽硅羟基, 有利于碱性物质的保留和分离, 表现出良好的亲水作用色谱性能. 将ZrO₂/SiO₂色谱柱用于4种脱氧核苷和5种碱性化合物的分离, 均得到了较好的效果, 展现出其作为色谱固定相良好的应用前景.     

芘基丁酸键合硅胶固定相对含π电子物质的高效液相色谱分离研究

通过芘基丁酸键合硅胶固定相对含π电子物质的分离研究, 考察了该固定相的色谱性能. 结果表明, 该固定相不仅具有疏水作用和电荷转移性能, 还具有很强的平面识别能力, 可很好地分离烷基苯、 稠环芳烃及取代硝基苯等各种含π电子物质， 且在pH 3.5～7.0 时化学稳定性能良好, 硅醇基效应得到了很好的抑制, 可有效地用于碱性化合物的分离分析.     

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.     

三元醇丙烯酰胺键合色谱固定相的制备及评价

利用巯基与乙烯基的"点击化学"反应合成了一种新型含多羟基的硅烷偶联剂,再将其与硅胶反应制得含多羟基的亲水固定相。经过元素分析表征证明多羟基官能团已成功键合到硅胶表面。采用一系列不同性质的标准物质考察了亲水色谱模式下固定相的溶质保留机理。由于固定相结构中既具有极性多羟基官能团,也有短的疏水碳链,因此固定相兼具疏水性与亲水性。将此固定相成功应用于亲水与反相色谱两种模式,并对比了两种模式下流速对柱效的影响。最后将固定相应用于烷基苯、水溶性维生素以及核苷的分离中,取得了较好的分离效果,证明了固定相良好的应用前景。     

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.     

The degree of substitution affects the enantioselectivity of sulfobutylether‐β‐cyclodextrin chiral stationary phases

Three chiral stationary phases were prepared by dynamic coating of sulfobutylether‐β‐cyclodextrin (SBE‐β‐CD) with different degrees of substitution, onto strong anion‐exchange stationary phases. The enantioselective potential and stability of newly prepared chiral stationary phases were examined using a set of structurally different chiral analytes. Measurements were performed in RP‐HPLC. Mobile phases consisted of methanol/formic acid, pH 2.10, and methanol/10 mM ammonium acetate buffer, pH 4.00, in various volume ratios. SBE‐β‐CDs with degrees of substitution (DS) 4, 6.3, and 10 proved suitable for the enantioseparation of 14, 11, and 8 analytes, respectively. The SBE‐β‐CD DS 4 based chiral stationary phase enabled the enantioseparation of the nearly all basic and neutral compounds. Chiral stationary phases with higher sulfobutylether‐β‐cyclodextrin substitution (especially DS 10) yielded higher enantioresolution values for acidic compounds.     

Characterization of a new stationary phase based on microwave immobilized polybutadiene on titanium oxide-modified silica

Titanium oxide-modified silica was prepared by reaction of silica with titanium tetrabutoxide and then was used as support in the preparation of stationary phases with self-immobilized polybutadiene (PBD) and PBD immobilized through microwave radiation. Chromatographic performance of the stationary phases was evaluated in terms of the efficiency (plates/m), asymmetry (A(s)), retention factor (k) and resolution (R(s)) of two standard sample mixtures, one of then containing the basic compound N,N-dimethylaniline. A microwave irradiation of 30 min at 520 W gave the best efficiency (86,500 N m(-1)), greater than that of a 6-day self immobilized phase (69,500 N m(-1)). Self-immobilized stationary phases prepared with bare silica were also studied for comparison. These resulted in lower chromatographic performance, 43,800 N m(-1), when compared to the self-immobilized phase prepared with titanized silica.     

Characterization of the properties of stationary phases for liquid chromatography in aqueous mobile phases using aromatic sulphonic acids as the test compounds

We investigated the effects of the concentration of naphthalene sulphonic acids (NSAs) as anionic test compounds in the injected sample and of the salt additives to the mobile phase on ion-exclusion. The retention behaviour of NSAs sensitively reflects even minor changes in the ionic and hydrophobic interactions and can be useful for predicting the effects of the stationary phases in reversed-phase chromatography of polar and ionic compounds, both small ones and biopolymers, e.g., oligonucleotides. We studied chromatographic properties of several stationary phases intended for separations in aqueous mobile phases: a C18 column end-capped with polar hydrophilic groups, a densely bonded C8 column doubly end-capped with short alkyl groups, a short alkyl stationary phase designed to keep full pore accessibility in highly-aqueous mobile phases and a Bidentate column with “bridged” C18 groups attached to the silica hydride support. The chemistry and pore structure of various types of column packing materials and of the salt additives to the mobile phase affect the proportion of the pore volume non-accessible to anions due to ion-exclusion and consequently the peak asymmetry and hydrophobic selectivity in reversed-phase chromatography of organic acids. We also addressed the problems connected with the determination of column hold-up volume in aqueous mobile phases. The accessibility of the stationary phase for anionic compounds in contact with the sample zone is affected by ion-exclusion due to repulsive interactions with the negatively charged surface in the pores of the stationary phase. The accessible part of the stationary phase increases and consequently the migration velocity along the column decreases with increasing concentration of the sample in the zone moving along the column. Because of a limited access to the stationary phase, its capacity can be easily overloaded. The combination of the column overload and ion-exclusion effects may result in fronting or tailing peak asymmetry. To explain this behaviour, we proposed a modified Langmuir model, respecting the variation of the column capacity due to the effects of sample concentration on ion-exclusion.     

Separation study of organic bases on new polymeric stationary phases under basic conditions

Crosslinked monodisperse polymer microparticles have been synthesized and evaluated as stationary phases for the separation of basic drug molecules in reversed-phase high performance liquid chromatography. The polymer beads were prepared by free-radical copolymerization of divinylbenzene and styrene or vinylbenzyl chloride in acetonitrile with toluene as porogen agent using the precipitation method. Their efficiency as stationary phase was investigated at both acid (5.6) and basic (12) pH, and the results compared with those of a commercial polymeric reversed-phase column. Separation of the organic bases was achieved with the chlorobenzyl particles at pH 12.     

一种可控离子比例的两性亲水色谱固定相的制备及性能研究

将不同比例的氨基和巯基的硅烷偶联剂键合到硅胶表面，再利用巯基与乙烯基膦酸之间的点击化学反应将膦酸基团引入到硅胶表面，制备了一种可调节正负离子比例的两性亲水色谱固定相。通过测定固定相中C、H、N、P元素的含量，证明了氨基与膦酸基团已成功键合到固定相的表面，同时通过N元素与P元素的质量分数确定固定相表面氨基与膦酸基团的比例。制备了3种不同电荷比例的氨基膦酸固定相，将其作为亲水模式下的固定相填料填装在150 mm×4.6 mm不锈钢色谱柱中。以一系列经典的极性小分子作为探针，研究了流动相中乙腈含量、缓冲盐pH值及缓冲盐浓度等因素对探针分子在3种色谱柱上的保留的影响，结果表明，分析物在固定相上是多重保留机理。最后通过比较核苷、水溶性维生素、碱性化合物、苯甲酸这几类标准物质在3种色谱柱上的保留行为来对比3种不同电荷比例的固定相的分离选择性与色谱性能。结果表明，对于不同的分析物，3种固定相表现出完全不同的分离选择性和色谱行为。可以根据分析物的特征选取不同电荷比例的固定相，表明此种固定相在极性化合物的分离上具有良好的应用前景。     

Novel chiral stationary phases based on peptoid combining a quinine/quinidine moiety through a C9‐position carbamate group

By connecting a quinine or quinidine moiety to the peptoid chain through the C9‐position carbamate group, we synthesized two new chiral selectors. After immobilizing them onto 3‐mercaptopropyl‐modified silica gel, two novel chiral stationary phases were prepared. With neutral, acid, and basic chiral compounds as analytes, we evaluated these two stationary phases and compared their chromatographic performance with chiral columns based on quinine tert‐butyl carbamate and the previous peptoid. From the resolution of neutral and basic analytes under normal‐phase mode, it was found that the new stationary phases exhibited much better enantioselectivity than the quinine tert‐butyl carbamate column; the peptoid moiety played an important role in enantiorecognition, which controlled the elution orders of enantiomers; the assisting role of the cinchona alkaloid moieties was observed in some separations. Under acid polar organic phase mode, it was proved that cinchona alkaloid moieties introduced excellent enantiorecognitions for chiral acid compounds; in some separations, the peptoid moiety affected enantioseparations as well. Overall, chiral moieties with specific enantioselectivity were demonstrated to improve the performance of peptoid chiral stationary phase efficiently.     

Selectivity of some basic solutes on a poly(methyltetradecylsiloxane)-silica stationary phase

Complex analyses of polar compounds, especially basic ones, require more selective stationary phases. The present paper describes a stationary phase prepared by thermal immobilization of poly(methyltetradecylsiloxane) onto chromatographic silica (PMTDS-SiO(2)). This stationary phase presents hydrophobic and ion-exchange interactions that confer both high retention and unique selectivities for basic solutes. The influence of ion-exchange interactions is confirmed by the increase in retention factors of basic solutes when the mobile-phase pH changes from acidic to neutral and by the decrease in retention factors when the mobile-phase pH changes from neutral to alkaline. The ion-exchange properties of the stationary phase are enriched in neutral mobile phase (pH 7-7.5) using soft Lewis bases such as tricine and tris as buffers but are suppressed in both acidic (pH 2.5-6) and highly alkaline mobile phases (pH≤10). Increasing both temperature and flow rate permits more rapid separations while maintaining the selectivity. The stability of the stationary phase is evaluated with acid, neutral and alkaline mobile phases.     

Preparation and characterization of a magnesia-zirconia stationary phase modified with β-cyclodextrin for reversed-phase high-performance liquid chromatography

A new stationary phase of magnesia-zirconia composite matrix for high-performance liquid chromatography was first prepared by modification of β-cyclodextrin (β-CD) via fosfomycin as a spacer. Various modification procedures were attempted for achievement of successful modification. The modified composite was characterized by using coloration, elemental analysis, diffused reflectance FT-IR, surface area and pore size distribution. The separation of alkylbenzenes, polycyclic aromatic hydrocarbons, positional isomers of some acidic, basic and amphoteric disubstituted benzenes was studied on the new stationary phase. The effect of pH and methanol content in the mobile phase on retention and separation selectivity for the positional isomers were investigated. The chromatographic performance of CD modified magnesia-zirconia was compared with fosfomycin modified magnesia-zirconia as intermediate material and bare magnesia-zirconia as raw material. The results show that various retention mechanisms such as hydrophobicity, inclusion complexation and hydrogen bond interaction exist in the chromatography process of the packing modified with CD. The β-CD played the major role in the chromatographic property of this new stationary phase. The modified magnesia-zirconia exhibits superiority of separation for basic aromatics and high stability above pH 11.     

Separation behavior of basic compounds on unbonded silicon oxynitride and silica high‐performance liquid chromatography stationary phases with reversed‐phase eluents

Unbonded silicon oxynitride and silica high‐performance liquid chromatography stationary phases have been evaluated and compared for the separation of basic compounds of differing molecular weight, pK_a, and log D using aqueous/organic mobile phases. The influences of percentage of organic modifier, buffer pH, and concentration in the mobile phase on base retention were investigated on unbonded silicon oxynitride and silica phases. The results confirmed that unbonded silicon oxynitride and silica phases demonstrated excellent separation performance for model basic compounds and both the unbonded phases examined possessed a hydrophobic/adsorption and ion‐exchange character. The silicon oxynitride stationary phase exhibited high hydrophilicity compared with silica with a reversed‐phase mobile phase. An ion‐exclusion‐type mechanism becomes predominant for the separation of three aimed bases on the silicon oxynitride column at pH 2.8. Different from silicon oxynitride stationary phase, no obvious change for the retention time of three model bases on silica stationary phase at pH 2.8 can be observed.