高效液相苯胺甲基键合硅胶固定相的保留机理研究

 制备了 3种不同键合量的苯胺甲基键合硅胶固定相 ,分别在正、反相条件下研究了它们对芳烃及其极性、酸性、碱性取代衍生物的保留和分离选择性 ,探讨了该固定相的保留机理 ,并考察温度对溶质在具有不同键合量的固定相上保留的影响。结果表明 :苯胺甲基键合硅胶固定相对溶质的保留是疏水、π π、偶极 偶极和电荷转移等多种作用的结果 ,在反相模式中 ,疏水作用对溶质的保留起主要作用。     

木糖醇和麦芽糖醇型亲水作用色谱固定相的制备及其分离性能的评价

利用-NCO和-OH的加成反应,通过简单的两步反应将木糖醇和麦芽糖醇成功地键合于硅胶表面,制备了两种新型糖醇类亲水作用色谱固定相。流动相中乙腈含量对保留的影响曲线表明,这两种糖醇固定相具有典型的亲水作用色谱固定相性质,对极性和亲水性化合物有很强的保留作用。利用这两种固定相成功分离了水溶性维生素、水杨酸及其类似物、碱基及其相应的核苷和淫羊藿苷类似物等模型混合物,同时糖醇固定相展现了新颖的选择性,特别是相对于线形的木糖醇键合固定相,非线形的麦芽糖醇键合固定相表现出了对糖基的独特保留能力。此外,缓冲盐的pH和浓度对保留的影响表明静电作用在这两种糖醇固定相的保留机理中也发挥着一定的作用。本文所发展的糖醇类固定相具有良好的分离性能,有望在亲水作用色谱分离领域发挥潜在的应用价值。     

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。     

咪唑侧基功能化聚离子液体修饰的混合模式色谱固定相的制备及其色谱性能

该文合成了咪唑侧基功能化的离子液体单体1-(4-乙烯基苄基)-3-氰甲基溴化咪唑盐,通过表面引发原子转移自由基聚合将该单体接枝到硅胶表面,制备了一种新型混合模式色谱固定相。采用红外光谱、元素分析及热重分析对其结构进行表征。该色谱固定相具有良好的分离能力。通过研究流动相pH对物质保留的影响,验证了物质在该固定相上存在反相-离子交换保留机理。通过与十八烷基硅烷键合硅胶固定相比较,证实了该聚离子液体固定相对物质保留提供了π-π作用。结果表明,对咪唑侧基功能化是制备新型离子液体固定相的可行方法。     

糖类化合物亲水作用色谱保留行为评价

以糖类化合物为研究对象,系统评价了其在亲水模式下的色谱保留行为。分别考察了流动相、固定相和缓冲盐等对糖类化合物保留的影响,建立了糖类化合物在亲水模式下的保留方程。结果表明,糖类化合物随着流动相中乙腈比例的降低,保留时间减小;随着缓冲盐浓度的增加,保留时间增加;同时,糖类化合物的保留行为还会受到有机溶剂种类和固定相类型的影响;其保留行为可使用顶替吸附-液相相互作用模型定量描述。将该模型进一步用于实际样品中糖类化合物保留行为的预测,获得了较好的实验结果,预测保留时间与实测保留时间的相对误差小于0.3%。对糖类化合物亲水模式下的保留行为进行了系统的评价和定量描述,该研究结果将有助于糖类化合物亲水作用色谱分离方法的发展。     

十二烷基键合氧化锆固定相的制备与性能评价

以自制5μm球形氧化锆为基质，制备了十二烷基键合氧化锆HPLC固定相，考察了正烷基取代苯、稠环芳烃、苯胺及吡啶衍生物、苯酚和硝基苯酚异构体等不同性质化合物在固定相上的保留行为，并与十二烷基键合硅胶固定相进行了比较。结果表明：中性和碱性化合物在固定相上主要为反相色谱保留机理；酸性化合物在固定相上以反相色谱保留机理为主，但是氧化锆表面的Lewis酸性中心对溶质也存在一定程度吸附作用，导致色谱峰拖尾。     

碱金属和碱土金属离子在反相高效液相色谱柱上的保留机理

发现以酒石酸和吡啶二甲酸等羧酸水溶液作淋洗剂时，钠，铵，钾，镁和钙等碱金属及碱土金属离子在ＯＤＳ反相高效液相色谱柱上有明显的保留，而且相互之间能达到一定程度的分离。单独用分配或疏水作用等反相高效液相色谱的保留机理难以解释其保留行为。为此，作者提出了动态包固定相机理，即认为羧酸根阴离子因其疏水性在ＯＤＳ固定相有保留，在固定相表面形成具有羧酸基阳离子交换树脂功能的动态包覆固定相。     

对-叔丁基-杯[4]芳烃键合硅胶及其它硅胶基质键合固定相的色谱保留性质

利用线性溶剂化能相关,在相同色谱条件下,研究了对-叔丁基-杯[4]芳烃键合硅胶固定相与其它硅胶基质键合固定相的反相色谱行为。结果表明,对-叔丁基-杯[4]芳烃键合硅胶固定相和其它固定相在保留机理上有很大不同。控制溶质保留的两个主要因素不是溶质的体积和氢键受体碱性,而是溶质的过剩摩尔折光率和氢键给体酸性。r系数值较大说明π-π作用对溶质的保留贡献较为明显,说明该新固定相对高极化率溶质如稠环芳烃具有较高的选择性。     

疏水作用色谱中流动相组成对溶质保留行为的影响

 首次研究了疏水作用色谱 (HIC)中芳香醇同系物在不同种类盐流动相中的保留行为。以计量置换保留模型中的参数Z分析了HIC中小分子与生物大分子保留行为的差别 ,以及不同流动相组成对两种类型溶质的洗脱范围及洗脱能力的影响。与反相色谱相似 ,芳香醇在HIC中的保留仍存在同系物规律。比较了小分子和生物大分子在不同盐溶液中的Z值变化 ,表明流动相中的盐仅改变小分子与固定相的水合程度 ,而对生物大分子 ,除改变其和固定相水合程度外 ,还会影响生物大分子与固定相接触区的分子构象     

亲水作用色谱及其在碱性药物分析中的应用

亲水作用色谱是采用极性固定相、高含量极性有机溶剂-水相缓冲液为流动相的一种分离技术，它能有效地保留反相色谱中保留弱或不保留的强极性碱性药物。本文综述了以未键合硅胶为固定相的亲水作用色谱分离碱性药物的机理、特点及其应用的最新进展。     

Adjusting the chromatographic properties of poly(ionic liquid)‐modified stationary phases by substitution on the imidazolium cation

Poly(ionic liquid)‐modified stationary phases can have multiple interactions with solutes. However, in most stationary phases, separation selectivity is adjusted by changing the poly(ionic liquid) anions. In this work, two poly(ionic liquid)‐modified silica stationary phases were prepared by introducing the cyano or tetrazolyl group on the pendant imidazolium cation on the polymer chains. Various analytes were selected to investigate their mechanism of retention in the stationary phases using different mobile phases. Two poly(ionic liquid)‐modified stationary phases can provide various interactions toward solutes. Compared to the cyano‐functionalized poly(ionic liquid) stationary phase, the tetrazolyl‐functionalized poly(ionic liquid) stationary phase provides additional cation‐exchange and π‐π interactions, resulting in different separation selectivity toward analytes. Finally, applicability of the developed stationary phases was demonstrated by the efficient separation of nonsteroidal anti‐inflammatory drugs.     

Insights into the retention mechanism of neutral organic compounds on polar chemically bonded stationary phases in reversed-phase liquid chromatography

The solvation parameter model is used to characterize the retention properties of a 3-aminopropylsiloxane-bonded (Alltima amino), three 3-cyanopropylsiloxane-bonded (Ultrasphere CN, Ultremex-CN and Zorbax SB-CN), a spacer bonded propanediol (LiChrospher DIOL) and a multifunctional macrocyclic glycopeptide (Chirobiotic T) silica-based stationary phases with mobile phases containing 10 and 20% (v/v) methanol-water. The low retention on the polar chemically bonded stationary phases compared with alkylsiloxane-bonded silica stationary phases arises from the higher cohesion of the polar chemically bonded phases and an unfavorable phase ratio. The solvated polar chemically bonded stationary phases are considerably more hydrogen-bond acidic and dipolar/polarizable than solvated alkylsiloxane-bonded silica stationary phases. Selectivity differences are not as great among the polar chemically bonded stationary phases as they are between the polar chemically bonded phases and alkylsiloxane-bonded silica stationary phases.     

Chemometric study of retention on binary stationary phases in gas chromatography

Using gas chromatography, data analysis is performed on a dataset consisting of 486 retention indices, 27 standards (ramified alkanes, aliphatic alcohols, and aromatic compounds), 6 pure and binary stationary phases, and three temperatures. The behavior of the pure stationary phases (OV-3, OV-225, OV-61-OH, and OV-1701-OH) and the binary stationary phases (OV-3/OV-225 and OV-61-OH/OV-1701-OH) at different temperatures (60°C-100°C) is investigated with factor and topological analysis. The influence of temperature and the nature of the mixed stationary phases on the retention indices is studied by correspondence factor analysis (CFA). The non-additivity of the retention properties of the pure phases used as mixed phases is clearly established by CFA. The topological analysis of the substituent's effect is investigated with a DARC/PELCO procedure and shows the particular influence of the stationary phase composition on the retention. The substituent effect is measured for the pure and binary stationary phases at various temperatures. The evolution of the substituent effect from the pure stationary phases to the binary phases is discussed.     

烃类化合物在不同色谱柱上的定量结构-保留相关性研究

运用量子化学中的AMI方法计算烃类化合物的分子结构描述参数,借助逐步回归法建立了烃类化合物在不同极性色谱柱上的QSRR模型。结果表明：烷烃、烯烃、二烯烃类化合物在不同极性的色谱柱上的色谱保留与其分子结构描述参数之间具有较好的线性关系,烃类化合物在不同极性固定相上的保留主要与溶质分子的MR有关,即与溶质分子的色散力有关。随着溶质分子的不饱和度的增加,或固定相极性的增强,溶质分子与固定相之间的电荷传递作用随之增强。而且,烃类化合物在不同极性固定相上的色谱保留的QSRR模型均可用量化参数HOMO、LUMO、EICE以及MR参数来描述。所建立的在不同极性色谱柱上的烃类化合物的色谱保留QSRR模型预测烃类化合物的色谱保留值时具有较好的稳定性和准确性。     

Characterization of several stationary phases prepared by thermal immobilization of poly(methyltetradecylsiloxane) onto silica surfaces

Variations of a thermal immobilization procedure using poly(methyltetradecilsiloxane) and silica produced fourteen stationary phases with carbon contents of 4-18%. The stationary phases were chromatographically evaluated with the Engelhardt, SRM 870 and Tanaka tests. Classifications using USP and Euerby procedures indicate that the new immobilized phases are different from most commercial phases although there was some similarity with phases that have high ion-exchange interactions. The retention mechanism involved in the separation of basic solutes on several of the new stationary phases was studied by varying pH, type of Lewis base and the ionic strength of the eluent. The separations are strongly influenced by the chemistry of the accessible free silanols. The stationary phases present good selectivity at intermediate pH where the basic analytes were protonated, suggesting use of intermediate pH for these separations. Stability tests show that the stationary phases have poor stability at very high pH, even at 23°C, but good stability in acidic mobile phases, even at 75°C, as expected for an immobilized polymer stationary phase.     

Preparation of pyrenebutyric acid bonded silica stationary phases for the application to the separation of fullerenes

A novel immobilization method was proposed for the preparation of pyrenebutyric acid-bonded silica (PYB-silica) stationary phases. The pyrene moiety was grafted to silica gel through spacers of aminoalkyl silanes. The HPLC separation of C60, C70 and higher fullerenes on the new pyrenebutyric acid-bonded silica stationary phases was also studied. Based on the temperature effect, the intermolecular interaction between stationary phases and solutes and the retention mechanism were discussed. The results of column loading capacity test demonstrated the potential for the separation of fullerenes in large amounts on the PYB-silica stationary phases.     

Analysis of Polycyclic Aromatic Hydrocarbons Formed During Off-Line Pyrolysis of Ergosterol by GC–MS–SIM

This work describes the preparation and characterization of two stationary phases based on the immobilization of poly(methyltetradecylsiloxane) onto doubly titanized silica particles. Chromatographic tests indicate that these metallized silica-based stationary phases present similar chromatographic performance for apolar and polar compounds to those obtained for their bare silica-based counterparts. Spectroscopic characterizations indicate high residual silanol quantities on titanized silica-based stationary phases; however, this fact does not contribute to a high asymmetry factor for basic compounds as is usually found with titania-based stationary phases. These stationary phases may be useful for analysis of pharmaceuticals.     

Quantitative evaluation of interactions of organic compounds with 18-crown ethers and β-cyclodextrin as components of stationary phases for gas chromatography

Individual stationary phases for gas chromatography based on 18-crown-6 and dibenzo-18-crown-6 (10% on Inerton N AW) and a stationary phase of a mixed composition (polyethylene glycol PEG-3000 and cyclodextrin β-CD) are prepared. These stationary phases are characterized using the McReynolds system and the Abraham solvation parameter model. It is shown that the solvation parameter model can be used to estimate the polarity of gas-chromatographic stationary phases based on the differences in intermolecular interactions between the studied gas-chromatographic stationary phase and the analyte during the separation process. Binary gas-chromatographic stationary phases based on glycerin and β-cyclodextrin with different concentrations of the macrocycle are studied at temperatures of 60 and 80°C, and the complexation constants of β-cyclodextrin with organic substances of various classes are calculated.     

气相色谱固定液极性和选择性评价

对非同族化合物溶质在两种固定相上保留值的关系进行了理论推导，并将该方程应用于８９种常见固定相的极性和选择性的评价。固定相的极性可用Ｂ值来评价，而选择性则用Ｂ、Ｔ３＾ａ，Ｃ３β值来评价。用该方程评价固定相具有两个优点，一是基于分子间作用力来评价固定相；二是探针化合物的选择不再受限制。     

Macrocycles as components of gas-chromatographic phases

The use of crown compounds (18-crown-6, benzo-18-crown-6, dibenzo-18-crown-6, benzo-15-crown-5, dibenzo-24-crown-8, 4,13-diaza-18-crown-6,4,13-dibenzyl-diaza-18-crown-6, and cryptand [2.2.2]) as components of stationary phases in the determination of organic compounds by gas chromatography is studied. The polarity, selectivity, efficiency, and working temperature ranges of stationary phases based on crown ethers and cryptand as well as conventional stationary phases for gas chromatography are compared. The influence of the type and number of heteroatoms, the conformational lability of the cavity, and the presence of substituents on the polarity and selectivity of the stationary phases under study is revealed. Preferable types of interactions of stationary phases containing crown compounds with organic compounds of different classes are discussed. It is concluded that phases of the mixed type based on crown ethers are promising for improving the selectivity and efficiency of gas-chromatographic separation