Phenylaminopropyl silica monolithic column for pressure assisted capillary electrochromatography

A novel stationary phase phenylaminopropyl silica (PhA-silica) monolith was successfully prepared for pressure assisted capillary electrochromatography (pCEC). The monolithic silica matrix from a sol-gel process was chemically modified by using [3-(phenylamino)propyl]trimethoxysilane as surface modification reagent to produce the phenylaminoporpyl function. The secondary amino groups on the surface of the monolithic stationary phase contributed to the generation of anodic electroosmotic flow (EOF) under acidic conditions. The phenyl group together with the spacer (-(CH(2))(3)-) in PhA-silica provides sufficient hydrophobic properties. To evaluate the column performance, effects of buffer pH and mobile phase composition on the mobile phase linear velocity and the retention factors of alkylbenzenes, phenols and anilines were investigated in pCEC mode. The monolithic stationary phases exhibit typical reversed-phase (RP) electrochromatographic behavior toward neutral solutes. Hydrophobic as well as electrophoretic migration process within the monoliths was observed for the separation of basic solutes such as anilines without peak tailing.     

Evaluation on the adsorption capabilities of new chemically modified polymeric adsorbents with protoporphyrin IX

A novel stationary phase — phenylaminopropyl (PLA) bonded silica — is proposed for anion-exchange chromatography. Low basicity (pK_a about 2.5) attached to silica phenylaminopropyl groups allows a variation of surface density of protonated sites in the pH range from 2 to 5. This enables us to use the same column for the separation of anions having different affinity to anion-exchangers. The effect of mobile phase pH on conditional capacity of PhA-silica was studied. The hypothesis on dependence of ion-exchange selectivity on the column capacity is discussed. Suitability of PhA-silica for ion-chromatographic separation of organic and inorganic anions at different pH values of eluent was demonstrated.     

Preparation and chromatographic performance of calix[4]crown-5 macrocycle-bonded silica stationary phase

A new calix[4]crown-5 macrocycle-bonded silica stationary phase (CL-CIMS) was prepared and applied at the same time to develop a chromatographic procedure to separate aromatic amines, phenols and drugs in this study. The chromatographic behaviors of the prepared stationary phase for these analytes were studied and compared with those of ODS (octadecylsilane). The effect of organic modifier content and pH of the mobile phase on retention and selectivity of these compounds were investigated. Some aromatic amines, phenols or drugs on CL-CIMS were successfully separated. The results show that CL-CIMS exhibits high selectivities for the above analytes in high aqueous mobile phases and a bright prospect in routine, fast separation of aromatic amines, phenols and drug compounds. From chromatographic data, it can be concluded that hydrophobic interaction is mainly responsible for the retention behavior as well as hydrogen-bonding interaction, π-π and dipole-dipole interaction.     

氨基甲酸酯功能化离子液体高效液相色谱固定相的制备与初步评价

合成一种了氨基酸衍生物：4,4′-二苯亚甲基桥联-二[2-(1-咪唑基)-3-苯基丙醇氨基甲酸酯](ImPh-Carb),并将其键合到硅胶上制备了一种新的氨基甲酸酯功能化的离子液体HPLC固定相（ImPh-Carb-Silica）。 利用1H NMR、13C NMR、MS和FTIR对ImPh-Carb进行了表征;通过FTIR和元素分析对ImPh-Carb-Silica固定相进行了表征,根据N含量计算得到ImPh-Carb-Silica的键合量为0.19 mmol/g。 以5种芳烃、5种酚类化合物和4种有机磷农药为分析物,分别在正相和反相色谱模式下对固定相的色谱分离性能进行了评价,同时考察了流动相的变化与溶质保留因子lg k之间的关系。 结果表明,该固定相与溶质分子间存在多重作用力,如疏水、氢键、π-π和偶极-诱导偶极作用等,使其能同时在正相和反相色谱模式下使用;在正相色谱条件下固定相对酚类化合物和有机磷农药表现出较好的分离选择性。     

A multiple-function stationary phase based on perhydro-26-membered hexaazamacrocycle for high-performance liquid chromatography

A perhydro-26-membered hexaazamacrocycle-based silica (L¹GlySil) stationary phase for high-performance liquid chromatography (HPLC) was prepared using 3-glycidoxypropyltrimethoxysilane as coupling reagent. The structure of new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic performance and retention mechanism of the new phase were evaluated in reversed-phase (RP) and normal-phase (NP) modes using different solute probes including aromatic compounds, organophosphorus pesticides, carbamate pesticides and phenols. The results showed that L¹GlySil was a sort of multimode-bonded stationary phase with excellent chromatographic properties. The new phase could provide various action sites for different solutes, such as hydrophobic, hydrogen bonding, π–π, dipole–dipole interactions and acid–base equilibrium. The presence of phenyl rings, secondary amino groups and alkyl linkers in the resulting material made it suitable for the separation of above-mentioned analytes by multimode retention mechanisms.     

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.     

High-performance liquid chromatography of sulfonamides and quinolones on p-tert-butyl-calix[6]arene-bonded silica gel stationary phase

The high-performance liquid chromatographic behavior of some sulfonamides and quinolones was studied on a p-tert-butyl-calix[6]arene-bonded silica gel stationary phase. The effect of mobile phase variables such as methanol content, ionic strength and pH on their chromatographic behavior was investigated. The retention behavior of sulfonamides on the stationary phase was compared with that on both Zorbax C₁₈-bonded silica gel and γ-(ethylenediamino)propyltriethoxylsilane-bonded silica gel (diamino-bonded phase). The retention mechanism of sulfonamides and quinolones on the stationary phase was also discussed. The results indicate that the stationary phase behaves as a reversed-phase packing and its separation selectivity is much better than that of not only Zorbax C₁₈ phase but also diamino-bonded phase. Some sulfonamides and quinolones were separated on the stationary phase, but the separation of sulfonamides is far more successful.     

一种聚合型弱阳离子交换/亲水相互作用色谱固定相的制备及色谱性能

通过亲核取代反应将聚乙烯马来酸酐键合到氨基硅胶表面,然后将残余的马来酸酐水解,制备了一种弱阳离子交换/亲水相互作用高效液相色谱固定相(Sil-PolyCOOH),通过固体核磁、ζ-电势及元素分析对固定相进行了表征。选取核苷和核酸碱为模型化合物,通过考察流动相组成,离子强度和pH等因素对溶质保留的影响,探讨了固定相的分离性能和保留机理,结果表明,该固定相的保留机理同时涉及亲水分配相互作用和多重主客体作用力。该固定相还对糖类、敌草快与百草枯等化合物具有良好的分离性能。上述研究结果表明该固定相在极性化合物的分离上具有良好的应用前景。     

奎宁功能化聚乙烯咪唑修饰硅胶亲水相互作用色谱固定相的制备及应用

通过表面自由基链转移聚合和亲核取代反应制备了一种新型奎宁功能化聚乙烯咪唑修饰硅胶亲水色谱固定相(Sil-PIm-Qn)。通过元素分析和红外光谱对该固定相进行表征,并在亲水相互作用色谱(HILIC)模式下对其进行了色谱性能评价。结果表明,该固定相对5种氨基酸、9种磺胺以及10种碱基核苷有较好的分离选择性。实验考察了流动相中有机相乙腈体积分数和水相中乙酸铵浓度对待分离物质保留行为的影响,并进一步对固定相分离的重复性进行了考察,其保留时间的相对标准偏差(RSD)为0.08%~2.30%(n=10)。该亲水色谱固定相制备方法简单,并且表现出了优异的亲水色谱分离性能,有望在磺胺类药物及生物样品中碱基核苷等亲水性物质的分离分析中有一定应用。     

High performance liquid chromatography with cyclodextrin and calixarene macrocycle bonded silica stationary phases for separation of steroids

β-Cyclodextrin, p-tert-butyl-calix[8]arene and chloropropyl bonded silica stationary phases have been prepared and were applied at the same time to develop a chromatographic procedure to separate steroids. In order to select the best type of stationary phase for the analysis, similar preparation processes of the two kinds of macrocycle stationary phases with the same spacer were adopted respectively. The chromatographic behaviors and retention mechanisms of the two kinds of macrocycle stationary phases for steroids were systematically studied and compared with those of chloropropyl bonded silica and ODS. The effect of mobile phase variables, such as methanol content, pH value of buffer, ionic strength and buffer composition on chromatographic behaviors was investigated. The results showed that the retention mechanisms of the four stationary phases for steroids were obviously different, and excellent separation was achieved on β-cyclodextrin bonded silica stationary phase (β-CD-BS), as a consequence of the structure and the properties of the stationary phase. The retention process on β-CD-BS exhibited inclusion complexation, hydrogen-bonding and weak hydrophobic interaction, while for p-tert-butyl-calix[8]arene bonded silica stationary phase (CBS), π-π and hydrogen-bonding besides hydrophobic interaction played an important role.     

L-异亮氨酸键合色谱固定相的制备及其性能

利用异氰酸丙基三乙氧基硅烷与L-异亮氨酸反应合成了一种新型的硅烷偶联剂,并进一步将其与硅胶反应制得键合有L-异亮氨酸的亲水色谱固定相。 通过核磁共振氢谱表明亮氨酸功能化硅烷偶联剂的成功合成、元素分析表征证明亮氨酸已成功键合到硅胶表面。 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,考察了这些探针分子在固定相上的色谱行为。 极性化合物的保留时间随着流动相中有机溶剂含量提高而逐渐增大,表现出典型的亲水保留特征。 进一步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分析物在固定相上的保留的影响。 在优化了相关参数后,将固定相应用于碱性化合物、水溶性维生素以及核苷类极性物质的分离当中。 在等度洗脱下,5种碱性化合物、6种水溶性维生素和8种核苷类物质分别在8、18及25 min内被成功分离。 分离结果表明了合成的L-异亮氨酸键合亲水色谱固定相具有较好的色谱性能,在极性化合物的分离上具有良好的应用前景。     

Preparation of a sulfoxide group and ammonium-salt bonded silica stationary phase for separation of polychlorinated biphenyls from mineral oils

In this study, a silica stationary phase modified with sulfoxide group and ammonium-salt was prepared for the separation of polychlorinated biphenyls (PCBs) from mineral oils, and its properties were investigated. Organic sulfide was attached to a diamino (primary and secondary amino) bonded silica surface by an amide bond, and the bonded sulfide groups were oxidized with periodate to afford sulfoxide groups bonded to the stationary phase. The secondary amino groups in the spacer chain were converted to ammonium-salt by the addition of hydrochloric acid. The sulfoxide group and ammonium-salt bonded stationary phase was tested for their suitability as adsorbent for SPE-type preparative short columns and for an analytical HPLC-type separation. The new stationary phase (1.2 mmol of sulfur bonded per gram) separated PCBs from mineral oils (paraffin-based transformer oils) more efficiently than previously reported stationary phases including sulfoxide group or ammonium-salt bonded ones. The quantitative chromatographic parameters for an aliphatic hydrocarbon (eicosane) and some PCB congeners also indicated strong retention of highly chlorinated biphenyls by the sulfoxide and ammonium-salt bonded silica compared with simple aminopropyl, sulfoxide group or ammonium-salt bonded ones. A cleanup procedure was established for simple determination of PCBs in mineral oil samples using sulfoxide group and ammonium-salt bonded silica packed column fractionation. The analytical method, combination of the cleanup procedure, and measurement with a GC-high resolution (magnetic sector) MS or a GC-quadrupole MS were validated using mineral oil certified reference materials.     

量子化学计算预测高效液相色谱键合相的保留机理

本文用Gaussian98计算软件中的Hartree—Fock方法对高效液相色谱中溶质与固定相发生作用后产生的能量进行计算,并对溶质与C18键合相和苯胺甲基键合相相互作用的计算结果与实验结论进行了比较。结果表明,量化计算结果与色谱保留行为之间具有相关性,即分子间相互作用能量的高低,决定了保留值的大小,表现为能量越负,保留值越大,而且双倍键合量的能量低于单倍键合量。量化计算的方法将为色谱保留性能的研究和键合相的研制提供参考。     

Silica based click amino stationary phase for ion chromatography and hydrophilic interaction liquid chromatography

A silica based amino stationary phase was prepared by immobilization of propargylamine on azide-silica via click chemistry. This readily prepared click amino stationary phase demonstrated good selectivity in separation of common inorganic anions under ion chromatography (IC) mode, and the triazole ring in combination with free amino group was observed to play a major role for separation of the anions examined. On the other hand, the stationary phase also showed good hydrophilic interaction liquid chromatography (HILIC) properties in the separation of polar compounds including nucleosides, organic acids and bases. The retention mechanism was found to match well the typical HILIC retention.     

Amino acid analysis by derivatization with chromogenic 4-phenylazobenzyloxycarbonyl chloride (PAZ-Cl): Comparison of reversed-phases

Summary The chromogenic reagent 4-phenylazobenzyloxycarbonyl chloride (PAZ-Cl) was used for the automated pre-column derivatization of amino acids (AAs) at ambient temperature followed by liquid chromatographic separation of the derivatives formed.Since in previous investigations it was realised that the selectivity of a C-18 stationary phase decreased after 40 injections of PAZ-AAs the suitability of 12 reversedphases distinguished by silica modification, carbon content, and particle characteristics was tested. Among these columns only a polymer-coated C-18 stationary phase furnished satisfactory repeatability of retention times for 250 analyses.     

Retention and selectivity properties of carbamate pesticides on novel polar-embedded stationary phases

This study describes the use of stationary phases with polar functionality suitable for the chemical analysis of carbamates pesticides and comparing with conventional alkyl C8 and C18 phases. The emphasis of this study was to compare the selectivity and retention of the pesticides on different stationary phases, bonded onto 1.7 μm partially porous silica particles under isocratic separation condition. Four stationary phases including: phenylaminopropyl (PAP) phase, bidentate propylurea-C18 (BPUC₁₈), C8 and C18, were successfully bonded on the partially porous silica spheres as evidenced by ²⁹Si and ¹³C solid-state NMR analysis. The phenylaminopropyl phase exhibited smaller retentivity and enhanced selectivity compared to the alkyl C8 phase; the analysis time to run separation of the six carbamate pesticides (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) on the PAP phase was threefold faster than alkyl C8 phase. In a similar manner, the BPUC₁₈ phase shows similar selectivity to that of the PAP phase, but with longer retentivity; although the BPUC₁₈ phase is characterized with a lesser degree of retentivity for the carbamate pesticides than the conventional alkyl C18 phase. We propose that π–π and weak polar interactions between the carbamate pesticides and the PAP phase dominates the separation mechanism and providing a superior selectivity; faster separation time was also achieved as a result of smaller retentivity. Whereas the C8 and C18 bonded phases exhibits only hydrophobic interactions with the pesticides, leading to larger retentivity. The BPUC₁₈ phase is shown to interact via polar–polar interactions in addition to hydrophobic interactions with the pesticides, providing similar selectivity with the PAP phase but with larger retentivity.     

Synthesis and evaluation of a maltose‐bonded silica gel stationary phase for hydrophilic interaction chromatography and its application in Ginkgo Biloba extract separation in two‐dimensional systems

Maltose covalently bonded to silica was prepared by using carbonyl diimidazole as a cross‐linker and employed as a stationary phase for hydrophilic interaction liquid chromatography. The column efficiency and the effect of water content, buffer concentration, and pH value influenced on retention were investigated. The separation or enrichment selectivity was also studied with nucleosides, saccharides, amino acids, peptides, and glycopeptides. The results indicated that the stationary phase processed good separation efficiency and separation selectivity in hydrophilic interaction liquid chromatography mode. Moreover, a two‐dimensional hydrophilic interaction liquid chromatography× reversed‐phase liquid chromatography method with high orthogonality was developed to analyze the Ginkgo Biloba extract fractions. The development of this two‐dimensional chromatographic system would be an effective tool for the separation of complex samples of different polarities and contents.     

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%).     

Selectivity differences of water‐soluble vitamins separated on hydrophilic interaction stationary phases

In this study, the retention behavior and selectivity differences of water‐soluble vitamins were evaluated with three types of polar stationary phases (i.e. an underivatized silica phase, an amide phase, and an amino phase) operated in the hydrophilic interaction chromatographic mode with ESI mass spectrometric detection. The effects of mobile phase composition, including buffer pH and concentration, on the retention and selectivity of the vitamins were investigated. In all stationary phases, the neutral or weakly charged vitamins exhibited very weak retention under each of the pH conditions, while the acidic and more basic vitamins showed diverse retention behaviors. With the underivatized silica phase, increasing the salt concentration of the mobile phase resulted in enhanced retention of the acidic vitamins, but decreased retention of the basic vitamins. These observations thus signify the involvement of secondary mechanisms, such as electrostatic interaction in the retention of these analytes. Under optimized conditions, a baseline separation of all vitamins was achieved with excellent peak efficiency. In addition, the effects of water content in the sample on retention and peak efficiency were examined, with sample stacking effects observed when the injected sample contained a high amount of water.     

新型咪唑嵌合氨基亲水作用色谱固定相的制备及其色谱性能

发展新型高效的亲水作用色谱分离材料对于极性化合物的分离分析具有重要的意义。本文设计合成了一种新型咪唑嵌合的氨基亲水作用色谱固定相（Sil-IEASP）,并分别采用傅里叶变换红外光谱仪、热重分析仪和元素分析仪对该固定相进行了表征,结果表明该固定相制备成功。以核苷和核酸碱基为样品,分别考察了流动相中的水含量、盐浓度和pH对其保留的影响,结果表明所发展的固定相具有良好的亲水作用特性;此外,缓冲盐浓度和pH几乎不影响上述物质的保留。进一步将该固定相应用于分离尿嘧啶、腺嘌呤、胞嘧啶、尿苷和3种位置异构体（邻三联苯、间三联苯和苯并菲）,与常用的氨基固定相相比,本文所发展的固定相具有更好的分离效果,有望在亲水作用色谱分离领域发挥潜在的应用价值。