Effect of stationary phase properties and solute molecular size on retention of PAHs in reversed-phase liquid chromatography

Summary The relationship between the retention of PAHs having various molecular sizes and the carbon contents (%) of bonded stationary phases with various types of ligands were investigated. The examined stationary phases were phenyl, diphenyl, triphenyl and benzyl-bonded silicas. The data indicated that sometimes it is not true that the retention of any solute relates linearly to the carbon content of the stationary phase. As the result, it is suggested that the pore size distribution of the silica support, the bulkiness of the ligand bonded to the silica and the molecular size of solute should also be considered before any precise statement can be made.     

姜黄素键合硅胶固定相的制备、表征及色谱性能

通过γ-［(2,3)-环氧丙氧］丙基三甲氧基硅烷(KH-560)偶联剂将具有抗菌功能的植物有效成分姜黄素键合到硅胶上,制备了姜黄素液相色谱键合硅胶固定相(CCSP)。采用元素分析、红外光谱和热分析对该固定相结构进行了表征。以甲醇和水为二元流动相,不同的中性、酸性和碱性化合物为溶质探针,并用ODS柱作参比,对固定相的色谱性能及保留机理进行了研究。研究结果表明,姜黄素键合固定相不仅具有良好的反相色谱性能,同时由于配体结构中所含有的基团形成了含芳环的共轭体系,从而引入了n-π和π-π作用位点,所含的羟基和β-二羰基与溶质之间存在偶极-偶极和氢键作用,与ODS相比,该固定相在极性化合物分离中占优势,且分析速度较快。     

An attempt directed toward enhanced shape selectivity in reversed-phase liquid chromatography: preparation of the dodecylaminated beta-cyclodextrin-bonded phase.

With the aim of preparing a stationary phase with a high shape-recognition ability for liquid chromatography, a new bonded phase was synthesized by coupling multiply dodecylamino-substituted beta-cyclodextrin (beta-CD) to 3-glycidoxypropyl-derivatized silica gel. The stationary phase prepared in this way was expected to have increased shape selectivity compared with that of conventional reversed-phase materials, due to solute interactions with the alkyl chain piles built up on the beta-CDs bonded to silica. The separation characteristics of the bonded phase were investigated using polycyclic aromatic hydrocarbons (PAHs) with different molecular shapes and compared with those of monomeric ODS and native beta-cyclodextrin-bonded phases. The newly developed stationary phase was found to be highly selective for PAHs.     

漆酚酯键合硅胶液相色谱固定相的制备与应用

以甲基丙烯酸漆酚酯为色谱配体,制备了一种新型色谱固定相。首先以漆酚和甲基丙烯酰氯为原料制备得到甲基丙烯酸漆酚酯,并通过物理吸附涂覆到由3-（甲基丙烯酰氧）丙基三甲氧基硅烷化学修饰的硅胶上,再通过自由基引发与硅烷化硅胶的双键聚合制得漆酚酯键合硅胶固定相（USP）。对固定相进行傅里叶红外光谱（FT-IR）、热重分析（TGA）、扫描电子显微镜（SEM）和元素分析（EA）表征,结果表明通过共聚反应成功地将漆酚酯固定在硅烷化硅胶上,且制备出的固定相具有良好的单分散性。采用匀浆法装柱,以乙腈-0.05%磷酸溶液（3：97,v/v）为流动相,流速为0.4 mL/min,检测波长为220 nm,考察固定相对天麻浸膏的分离性能。以乙腈-水（50：50,v/v）为流动相,流速为0.5 mL/min,检测波长为290 nm,考察固定相对吴茱萸浸膏的分离性能。结果表明该固定相对天麻浸膏和吴茱萸浸膏均具有良好的分离性能,从天麻浸膏中分离出5个色谱峰,从吴茱萸浸膏中分离出2个色谱峰。与商品化C₁₈ 柱相比,USP柱可以从天麻浸膏中分离出更多的有效组分并实现基线分离,分离吴茱萸浸膏的色谱条件更为环保和安全。采用低流速对天麻浸膏和吴茱萸浸膏进行分离,减少了流动相的使用量,分离结果令人满意。以天然产物漆酚制备色谱固定相,既为分离纯化天麻素和吴茱萸碱提供了一种新的方法,又为液相色谱固定相制备提供了新的思路,还拓展了生漆在色谱分离材料方面的应用。     

Correlation of the retention data of polyaromatic hydrocarbons obtained on various stationary phases used in normal- and reversed-phase liquid chromatography

Summary The correlation between the retention data of polyaromatic hydrocarbons (PAH) obtained in normal-and reversed-phase liquid chromatography is investigated in order to determine the dominant factors controlling the retention. It is clear that the separation of PAHs on various chemically-bonded packing materials in normal- and/or reversed-phase modes is primarily controlled by the molecular structure and shape. The -electron interaction between the solute and the stationary phase also contributes to the retention, although pure silica shows a somewhat different behavior.     

腰果酚键合硅胶固定相的制备及其色谱性能北大核心CSCD

天然产物作为一种绿色低毒、来源广泛、功能位点丰富的单体,已被广泛应用于色谱固定相的研制与开发。该文以天然可再生资源腰果酚为配体,通过一步法开环反应将其接枝到由γ-缩水甘油醚氧丙基三甲氧基硅烷(KH-560)修饰的硅胶上,制备得到腰果酚键合硅胶固定相。利用傅里叶红外光谱、元素分析、热失重分析和N_(2)吸附脱附实验对固定相进行表征,结果表明成功制备了腰果酚键合硅胶色谱固定相。采用Tanaka实验试剂、烷基苯、多环芳香烃、苯酚类化合物和芳香族位置异构体为探针评价其分离性能和保留机制,并与C_(18)柱进行对比。研究发现,腰果酚键合固定相除疏水作用外,还具有π-π和氢键作用。基于上述保留作用,腰果酚键合硅胶固定相对测试探针表现出良好的分离性能。重复进样10次,各探针保留时间的RSD为0.052%~0.079%,峰面积的RSD为0.104%~0.847%,峰高的RSD为0.081%~0.272%,表明该色谱柱具有良好的重复性和稳定性。此外,腰果酚键合硅胶色谱柱对中药喜树果和吴茱萸果的粗提物具有良好的分离性能,验证了其在实际样品分析中的巨大潜力。将天然产物腰果酚用于色谱固定相的制备,为分离纯化喜树碱和吴茱萸提供了新的方法,同时拓展了腰果酚在色谱分离材料方面的应用。     

大黄素键合硅胶高效液相色谱柱的制备和应用

采用中间体法,先将大黄素配体与γ-[（2,3）-环氧丙氧]丙基三甲氧基硅烷（KH-560）偶联剂反应制备含配体的硅氧烷试剂,然后再与硅胶键合,最终制得大黄素键合硅胶液相色谱固定相（以下简称ESP）。通过红外光谱、元素分析和热重分析表征固定相的结构。以萘作为溶质探针,甲醇-水（60：40,v/v）为流动相,流速为0.8 mL/min,测得ESP柱的柱效。采用传统的反相C₁₈和苯基柱作参比,将ESP应用于系列中性、碱性和酸性芳香族化合物以及实际样品风油精的分离分析,并探讨相关的色谱分离机理。结果表明,配体大黄素被成功地键合到球形硅胶表面,测得配体键合量为0.23 mmol/g,ESP柱理论塔板数约为19874 N/m。ESP的偶联剂链和蒽醌环提供了疏水性的结构基础,大黄素配体还能为溶质提供π-π或p-π、电荷转移、氢键、偶极-偶极等作用点。多位点的协同作用使得ESP柱具有独特和优秀的色谱分离选择性,并且无需调节pH值,采用简单而廉价的甲醇-水流动相就能实现胺类、酚类等极性样品的基线分离,实验条件简单、方便。     

Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. I. Chloro-added PAHs

Summary Retention characteristics in normal phase HPLC of highly biologically active chloro-added polycyclic aromatic hydrocarbons (PAHs) were studied. Silica, cyanopropyldimethylsilyl- and aminopropylsilyl- modified stationary phases were investigated. Retention properties of chloroadded PAHs on these phases were shown to be strongly influenced by the number of chloro-additions. This is due to the strong polarity of the methylene carbon at the chloro-addition site. Active silica had a strongly degrading effect on the unstable chloro-added PAHs during separation. Aminopropylsilica did not exhibit sufficient selectivity towards chloro-added PAHs when compared to chlorosubstituted PAHs. Cyanopropyldimethylsilica was shown to be applicable to a group separation of chloro-added and chloro-substituted PAHs. A fast clean-up procedure for chloro-added PAHs in complex samplesis outlined. It involves an initial elimination of more polar substances on a short open column with strongly deactivated silica and a subsequent separation on a cyanopropyldimethylsilyl HPLC column in normal phase mode.     

Immobilized metal-ion affinity chromatography of peptides on metalloporphyrin stationary phases

The retention of selected dipeptides and tripeptides containing tyrosine was examined. As stationary phase an aminopropylated silica gel loaded with covalently linked tetraphenylporphyrin was used. The effect of metalization of porphyrin with Cu(II) and Zn(II) on retention was investigated. The observed separation is based on a mixed mechanism involving π-π and hydrophobic interactions as well as complex formation between immobilized metal ions and peptides. A satisfactory separation was demonstrated for C-peptide and bovine insulin. The possibility of separation of various insulins was also investigated. Received: 10 August 1998 / Revised: 21 December 1998 / Accepted: 28 December 1998     

Immobilized metallacarborane as a new type of stationary phase for high performance liquid chromatography

A new type of high performance liquid chromatography (HPLC) stationary phase was prepared, and its chromatographic properties were evaluated. The sorbent was composed of metallacarborane covalently bound to silica. Because of the chemical structure of the immobilized metallacarborane, the synthesized stationary phase was able to interact with nonpolar analytes via hydrophobic interactions. The chromatographic behavior of several low-molecular-weight hydrocarbons on the sorbent under typical reversed-phase conditions was compared with octadecyl-, sulfo phenyl- and aminopropyl-modified silica stationary phases. Moreover, as a consequence of the synthetic protocol employed, the immobilization of the metallacarborane led to the development of a zwitterionic chemically bonded phase, which demonstrated excellent resistance to "phase collapse" in a 100% aqueous environment. Finally, preliminary experiments indicated that the new stationary phase has the potential for utilization in hydrophilic interaction chromatography (HILIC) mode for the separation of polar compounds.     

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.     

HPLC-separation of enantiomers using quinine,covalently bonded to silica as stationary phase

Summary Stationary phases for chiral separations have been synthesized by chemical modification of porous small particle silica using new procedures of fixation of the chiral moiety. So called pre-polymers of the methylpolysiloxane polysiloxane type are immobilized on silica surfaces by different procedures. These pre-polymers are substituted by chiral groups. Their synthesis is done externally i.e. not in-situ on the support surface. The immobilization on the silica surface is achieved by crosslinking and/or by chemical bonding. Anchor groups within the pre-polymer (e.g. SiH) as well as on the silica surface (SiOH) give rise to the chemical bonding therewith. Chiral phases with quinine as the chiral moiety were obtained which show high separation efficiency as well as chemical stability, in addition to the enantiomeric selectivity required for the separation of certain types of aliphatic and aromatic alcohols. Presented at the 16th International Symposium on Chromatography, Paris, September 1986     

一种混合模式反相弱阳离子交换色谱填料的制备及其保留机理

采用“点击化学”的合成方法制备了一种混合配体的辛基-羧基共同键合硅胶（OCS）材料,经元素分析和红外光谱表征,证明了辛基和羧基官能团均已成功键合到硅胶表面。将其作为混合模式反相弱阳离子交换（RP/WCX）的固定相填料,以3种同系物阳离子表面活性剂作为探针分子,定量研究了该固定相的混合模式保留机理,考察了溶质保留因子与盐浓度和溶质亚甲基数目的关系,验证了混合模式固定相的单点和两点保留机理的数学模型,并进一步将其应用于一系列标准碱性混合物的分离。结果表明：两点保留机理更加符合实验的结果;根据混合模式两点保留机理的数学方程,可以得到单一的疏水或离子交换作用力对总保留的影响,对混合模式色谱的实际分离应用提供了有价值的参考。本文建立了反相弱阳离子交换混合模式OCS固定相的保留机理的定量模型,并证明了该固定相在碱性化合物的分离中具有很大的应用前景。     

Carbon nanotube immobilized polar membranes for enhanced extraction of polar analytes

We demonstrate for the first time that carbon nanotubes (CNTs) can be readily immobilized on the surface of a solid polymeric membrane which can lead to enhanced enrichment factor and extraction efficiency. The effectiveness of the CNT mediated process is demonstrated by micro-scale membrane extraction via direct solvent enrichment of polar and nonpolar organics. The enrichment factor measured as the ratio of concentrations in the acceptor to the donor phases was as high as 282 and the enhancement over the unmodified membrane was as much as 92%. In addition, the solvent retention in the carbon nanotube immobilized membrane (CNIM) increased by as much as 29%. Overall, the CNT incorporation provided enhanced solute transport and thus led to overall performance enhancement.     

厚朴酚键合硅胶高效液相色谱固定相分离嘌呤、嘧啶、蝶呤及黄酮

将新制备的厚朴酚键合硅胶固定相(MSP)用于嘌呤、嘧啶、蝶呤及黄酮类化合物的液相色谱分离分析。选取了4种嘌呤、8种嘧啶、4种蝶呤及5种黄酮类药物作为极性化合物的代表,以商品反相碳十八烷基键合硅胶柱(ODS)作参照,研究了新固定相对碱性化合物的选择性和相关分离机理。实验发现,在简单流动相条件下,厚朴酚键合硅胶固定相对上述药物表现出较高的选择性及分离效果。尽管MSP没有进行封尾处理,但含氮类极性化合物(嘌呤、嘧啶、蝶呤)仍表现出基本对称的色谱峰形。多数药物在两柱上的洗脱顺序大致相同,说明疏水作用始终存在,这说明新固定相具有反相色谱性能。比较研究还发现,MSP在分离上述极性药物时能够提供除疏水性作用之外的其他作用位点。例如,在分离嘌呤、嘧啶及蝶呤时,氢键和偶极作用明显存在;同时MSP与溶质结构中的芳环(硫唑嘌呤、紫花牡荆素)之间有较强的π-π电子相互作用等,使得含氮类极性化合物和黄酮的保留一般比ODS强,分离度也有一定的改善。多种作用可以合理地解释MSP柱对极性溶质有更强的分离能力,厚朴酚键合硅胶固定相可在一定程度上弥补ODS单一疏水作用的不足,有利于分类碱性化合物。     

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。     

大黄素键合硅胶固定相的制备及其在核苷碱基药物分离中的研究

通过γ-[(2,3)-环氧丙氧]丙基三甲氧基硅烷(KH-560)偶联剂将具有抗菌功能的植物有效成分大黄素键合到硅胶上,制备了大黄素液相色谱键合固定相(EDSP)。采用元素分析、红外光谱和热分析对该固定相的结构进行表征。以嘧啶、嘌呤和核苷为溶质探针,并用ODS柱做参比,对固定相的色谱性能及保留机理进行了研究。研究结果表明,该固定相具有类似ODS的反相色谱性能,除疏水作用外,由于大黄素的大π共轭体系,为溶质提供了n-π和π-π作用位点;且两个邻位羟基和两个羰基的存在,能够与溶质之间发生氢键作用和偶极-偶极作用。与ODS柱相比,该固定相在极性化合物分离中占优势,且分析速度较快。此外,实验还发现,该固定相能较好地分离二甲苯同分异构体,预示着该固定相有一定的立体选择性分离能力。     

Synthesis, characterization and structure effects on selectivity properties of silica gel covalently bonded diethylenetriamine mono- and bis-salicyaldehyde and naphthaldehyde Schiff(,)s bases towards some heavy metal ions

Four silica gel-immobilized new metal chelate Schiff(,)s bases were synthesized (I-IV). Silica gel chemically bonded diethylenetriamine mono-naphthaldehyde and mono-salicyaldehyde Schiff's bases (phases I and III) were produced via the interaction of silica gel-modified diethylenetriamine with naphthaldehyde and salicylaldehyde, respectively. However, phases II and IV arose through the interaction of bis-naphthaldehyde and bis-salicylaldehyde Schiff(,)s bases of diethylenetriamine with 3-chloropropyltrimethoxysilane modified silica gel. The characterization of such new phases, their capabilities towards selective extraction or separation of Fe(III), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions were studied and evaluated by both batch and column techniques as a function of pH and time of contact. Phases III and I showed high performance towards Cu(II) extraction, where their Cu(II) sorption determined to be 0.957 and 0.940 mmol g(-1), respectively. However, for phases IV and II, the great affinity was devoted to Fe(III) extraction followed by Cu(II) ions. The reactivity of metal ion sorption was discussed in the light of effects of bulkiness as well as orientation of immobilized chelate on sorbent reactivity. Donor sites of phases III and I (diethylenetriamine and azomethene nitrogens along with phenolic hydroxyl group oxygen) are fully active, whereas phases IV and II are partially active with only participation of oxygen and azomethene nitrogen. The order of increasing thermal stability (IV相似文献   

Factors affecting the reversed-phase liquid chromatographic separation of polycyclic aromatic hydrocarbon isomers

Reversed-phase liquid chromatography (LC) on C₁₈ stationary phases provides excellent selectivity for the separation of polycyclic aromatic hydrocarbons (PAH). Recent studies have shown that several factors affect selectivity for the LC separation of PAH including phase type (monomeric or polymeric), pore diameter and surface area of the silica substrate, and surface density of the C₁₈ ligands. In this paper the separation of eleven PAH isomers of molecular weight 278 is used to further illustrate the effect of stationary phase characteristics and shape of the solute (length-to-breadth ratio, L/B) on retention and selectivity. Only polymeric C₁₈ phases with a high C₁₈ surface coverage provided separation of all eleven isomers and the elution order of these isomers generally followed increasing L/B values. The effect of solute nonplanarity on reversed-phase LC retention was investigated on both monomeric and polymeric phases using a series of planar and nonplanar PAH pairs. For each solute pair, the nonplanar solute eluted earlier than the planar solute, the largest selectivity factors being observed on the C₁₈ phase with the highest percent carbon load. Based on these studies, a model is proposed to describe the retention of PAH on polymeric C₁₈ phases.