量化计算辅助解析杯[4]芳烃固定相对萘胺和苯二胺的保留机制

杯芳烃对客体具有优异的识别作用,可作为液相色谱的固定相．本文以萘胺（NA）、苯二胺（BDA）位置异构体为溶质探针,考察其在杯[4]芳烃（Cx4）固定相上的色谱分离,用量子化学计算辅助研究了其在Cx4芳烃固定相上的保留机制．结果表明,用DFT-B3LYP／STO-3G＊＊量化计算方法,获得了质子化溶质与Cx4形成的Cx4．HBDA＋、Cx4-HNA＋超分子结构,直观地观察到了HBDA＋、HNA＋与Cx4的作用主要是π-π疏水作用和氢键作用．超分子Cx4-HBDA＋和Cx4-HNA＋的ΔG数值、稳定性与其色谱保留行为一致．     

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。     

多壁碳纳米管键合硅胶固定相的保留机理研究

制备了3种不同键合量的多壁碳纳米管键合硅胶固定相。以芳香族化合物为目标分析物,甲醇-水为流动相,分别考察了其在不同流动相比例、流速、柱温条件下,酸性、中性、碱性化合物的色谱保留行为,并通过计算分离过程中焓变、熵变和吉布斯自由能等热力学参数,探讨了色谱柱的保留机理。结果表明,碳纳米管键合硅胶与未键合的硅胶固定相分离对氨基苯磺酸和尿嘧啶时,因碳纳米管的加入增强了其疏水作用,保留机理与反相色谱柱相似。而分离中性化合物时,因加入的碳纳米管引入π-π作用,增强了对化合物的保留,有效地提高了色谱柱的柱效。碳纳米管的加入使溶质分子在固定相上的保留增强,溶质分子从杂乱无序排列转为有序排列,且溶质分子在不同碳纳米管键合量的色谱柱上的保留并非由单一机理支配,而是由多种作用相互协同的结果,这使碳纳米管键合硅胶固定相在分离和固相萃取领域展现出良好的应用前景。     

柱温对胆固醇键合固定相分离黄酮苷的影响及其热力学分离机理研究

柱温属于高效液相色谱(HPLC)的可调参数之一,但在实际操作过程中,柱温对溶质保留行为的影响通常被忽略,不作为色谱条件优化参数.本研究分别以甲醇-0.02 mol/L乙酸(30∶70,V/V)及甲醇-0.02 mol/L乙酸(25∶75,V/V)为流动相,讨论了柱温对6种黄酮苷在一种新型色谱固定相-胆固醇键合固定相以及C18键合固定相上分离的影响.结果表明,随着柱温升高,不同于十八烷基键合固定相,黄酮苷在胆固醇键合固定相上的分离效果得到改善,且峰形变好.同时,拟合了25℃～55℃温度范围内的van't Hoff方程,从热力学角度比较了黄酮苷在胆固醇键合固定相和十八烷基键合固定相上的保留机理.结果表明,黄酮苷在两种色谱柱上的van't Hoff方程均具有良好的线性关系(R2 ＞0.99),且拟合参数相近(△H0＜0,△S0＜0),表明这些物质在胆固醇键合固定相上的保留机理与在十八烷基键合固定相上相似,以单一的疏水性保留机理为主导,均属于焓驱动过程.本实验证实,在使用胆固醇键合固定相时,柱温可作为一项重要调节参数,参与色谱优化过程,从而使液相色谱从两变量调节方式(流动相种类和流动相比例)变为三变量调节方式(流动相种类、比例和柱温),从而为色谱条件优化提供了更多选择.     

大黄蒽醌衍生物在杯[8]芳烃键合固定相上色谱行为的研究

研究了药用掌叶大黄中5种蒽醌衍生物在对-叔丁基杯[8]芳烃硅胶键合固定相上的高效液相色谱行为,并与ODS固定相进行了比较。研究发现这类化合物与杯[8]芳烃固定相之间存在多种相互作用,除疏水作用外,分离过程中还存在与ODS不同的色谱分离机制。杯芳烃键合相与溶质之间的氢键作用、包容络合作用改变了杯芳烃固定相对它们的选择性。     

衍生化环糊精键合固定相对N-苄氧甲酰基-α-氨基膦 酸酯化合物色谱保留和手 性识别机理的研究

正相条件下,一系列N-苄氧甲酰基-α-氨基膦酸二苯酯化合物首次在苯基氨基甲酸酯衍生化β环糊精键合硅胶固定相上实现了高效液相色谱手性拆分,结合热力学模型,对手性分离过程的热力学行为进行了讨论。探索运用定量结构-对映异构体选择性保留关系的方法,将对映异构体的色谱保留和溶质分子描述参数相关性闻系建立定量方程,从超热力学模型的角度研究了色谱保留和手性识别机理。     

衍生化环糊精键合固定相色谱保留和手性识别机理的研究(Ⅱ)

合成了苯基氨基甲酸酯衍生化β-环糊精键合固定相CSP1和CSP2，在正相色谱条件下，一系列α-氨基膦酸酯化合物首次在这类衍生化β-环糊精固定相上实现了手性拆分。探索运用定量结构-对映异构体选择性保留关系的方法，将对映异构体的色谱保留和溶质子描述参数进行相关性联系建立定量方程，对比研究了该类苯基氨基甲酸酯生化β-环糊精键合固定相上可能的液相色谱保留和手性识别机理。     

核苷与碱基的苯胺甲基键合硅胶固定相高效液相色谱分离

建立苯胺甲基键合硅胶固定相(PAMS)高效液相色谱分离核苷与碱基的方法；研究流动相有机溶剂浓度、磷酸缓冲液pH值、离子强度对核苷和碱基在该键合固定相上的色谱保留及分离选择性的影响，用磷酸缓冲液(pH＝4)为流动相快速分离了部分核苷与碱基。     

衍生化环糊精键合固定相色谱保留和手性识别机理的研究(Ⅰ)

合成了苯基氨基甲酸酯衍生化β-环糊精键合固定相,14个α-氨基膦酸酯类化合物首次在该固定相和商品化的(S)-(+)-萘乙基氨基甲酸酯衍生化β-环糊精固定相上进行液相色谱手性拆分.通过定量结构-对映异构体保留关系对比研究了两种不同的环糊精类固定相上可能的色谱保留和手性识别机理.     

一种手性中间体在键合型和涂覆型纤维素手性固定相上的拆分

制备了涂覆型和键合型纤维素-(3, 5-二甲基苯基氨基甲酸酯)固定相, 分别在制备的纤维素手性固定相上成功地拆分了一种手性中间体, 通过考察流动相中的改性剂(醇、四氢呋喃、三氯甲烷)对手性拆分的影响, 优化了手性中间体在两种手性固定相上的色谱分离条件, 并比较了手性中间体在涂覆和键合型纤维素手性固定相上的拆分. 结果表明, 涂覆型和键合型手性固定相对这种手性中间体均有较好的拆分效果, 在150 mm的色谱柱上, 这两种手性固定相对这种手性中间体的拆分能力相差不大, 但键合型固定相上可选择的流动相范围更广.     

Investigation on the preparation and chromatographic behavior of a new para-tert-butylcalix[4]arene-1,2-crown-4 stationary phase for high performance liquid chromatography

In the present work, a new para-tert-butylcalix[4]arene-1,2-crown-4 bonded silica stationary phase (CBS4-4) was synthesized, structurally characterized, and employed to separate polycyclic aromatic hydrocarbons (PAHs), phenols, aromatic amines, benzoic acid and its derivatives. The chromatographic behaviors of the prepared stationary phase were investigated and compared with ODS. The effects of methanol concentrations on the retention index show that CBS4-4 exhibits high selectivity for the above analytes. The separation mechanisms based on the different interactions between calixarene and the analytes were discussed. With the assistance of quantum chemistry calculation, the interaction Gibbs free energy change ΔG_solv (in the mobile phase) of p, m and o-phenylenediamine positional isomers and para-tert-butylcalix[4]arene-1,2-crown-4 were obtained. The ΔG_solv values were consistent with the retention behavior of p, m and o-phenylenediamine on the CBS4-4. According to the chromatographic data, it can be concluded that the selectivity of CBS4-4 for analytes is mainly ascribed to hydrophobic interaction, accompanied by other effects such as hydrogen bonding interaction, π-π and inclusion interaction. The CBS4-4 column has been successfully employed for the analysis of benzoic acid in Sprite drink.     

Preparation and characterization of six calixarene bonded stationary phases for high performance liquid chromatography

Six calixarene bonded silica gel stationary phases were prepared and characterized by elemental analysis, infrared spectroscopy and thermal analysis. Their chromatographic performance was investigated by using PAHs, aromatic positional isomers and E- and Z-ethyl 3-(4-acetylphenyl) acrylate isomers as probes. Separation mechanism based on the different interactions between calixarenes and analytes were discussed. The chromatographic behaviors of those analytes on the calixarene columns were influenced by the supramolecular interaction including pi-pi interaction, space steric hindrance and hydrogen bonding interaction between calixarenes and analytes. Notably, the presence of polar groups (-OH, -NO(2) and -NH(2)) in the aromatic isomers could improve their separation selectivity on calixarene phase columns. The results from quantum chemistry calculation using DFT-B3LYP/STO-3G* base group were consistent with the retention behaviors of PHAs on calix[4]arene column.     

Characteristics of lithium iodide-containing poly(ethylene glycol) as a gas chromatographic stationary phase, and its application to analysis of amidic drugs

The characteristics of lithium iodide-containing poly(ethylene glycol) as a gas chromatographic stationary phase have been evaluated in terms of partial free energy of transfer (delta G t0) from poly(ethylene glycol) to the lithium iodide-poly(ethylene glycol) system for a variaty of amides (n-fatty acid amides, lactams, benzamides, anilides, nicotinamides, isonicotinamides, barbiturates, pyrazolones) and several amines. The changes in relative retention and resolution of two solute peaks caused by the addition of lithium iodide to poly)ethylene glycol) are correlated with the difference in their delta Gt0 values. The application to the specific separation of some amidic drugs is demonstrated.     

氧化锆及铈-锆复合氧化物的阴离子交换和配体交换色谱性能

高效液相色谱法;氧化锆及铈-锆复合氧化物的阴离子交换和配体交换色谱性能     

Effect of Buffer Constituents on Retention and Separation in Achiral and Chiral HPLC Systems with β-Cyclodextrin-Based Stationary Phase

In HPLC, cyclodextrin-based stationary phases allow separation of both achiral and chiral analytes. Complexation of analytes into the cyclodextrin cavity is a very important part of the interaction mechanism. However, possible complexation of buffer constituents must be also considered. This fact should not be overlooked in method development procedures. In this study, β-cyclodextrin-based stationary phase (CYCLOBOND I 2000) was used, and two different buffers, namely aqueous solutions composed of lithium hydroxide/benzoic acid 10.0/24.5 mM, pH 4.00 and lithium hydroxide/acetic acid 9.9/60.0 mM, pH 4.01 of the same ionic strength were compared. Methanol was added as organic modifier in a methanol/buffer volume ratio 40/60. The linear free energy relationship method was used for evaluation of interactions contributing to chromatographic performance of the separation system. Strong complexation of benzoic acid with cyclodextrin was obvious from the results. This effect was clearly reflected in reduced retention and restricted (enantio) separation ability of the separation system containing benzoic acid in the buffer. On the other hand, complexing buffer constituents of mobile phases can offer a worthy alternative, to less “green”organic solvents, for reduction of the analysis time.

     

(4-环戊二烯基苯甲酸-铁-甲苯)六氟磷酸盐键合硅胶固定相的制备及色谱性能

基于二茂铁独特的分子结构及其作为新型液相色谱分离基质的潜质,制备了新型(4-环戊二烯基苯甲酸-铁-甲苯)六氟磷酸盐键合硅胶固定相,利用红外光谱、元素分析、热重分析等手段对其进行了表征。分别选取多环芳烃、萘胺位置异构体、硝基苯胺位置异构体、硝基咪唑类化合物和有机磷化合物溶质作为探针,对其色谱性能进行了评价。结果表明,该色谱固定相能提供 π-电子转移、 π-π 作用、偶极-偶极作用及与底物的静电相互作用等多种作用力,并探讨了可能的分离机理。     

Enantioseparation of phenylalanine analogs on a quinine-based anion-exchanger chiral stationary phase: structure and temperature effects

Application of a cinchona alkaloid-based chiral anion-exchanger stationary phase for the direct high-performance liquid chromatographic enantioseparation of N-protected unusual phenylalanine analogs is reported. The N-benzyloxycarbonyl, N-3,5-dinitrobenzyloxycarbonyl, N-benzoyl and N-3,5-dinitrobenzoyl derivatives were well separable with high resolution. To achieve optimal separation of the enantiomers, the chromatographic conditions and temperature were varied. Linear van't Hoff plots were observed in the studied temperature range, 278-343 K, and the apparent changes in enthalpy, delta(deltaH degrees), entropy, delta(delta S degrees), and Gibbs free energy, delta(delta G degrees), were calculated. The values of the thermodynamic parameters depended on the nature of the N-acyl groups, on the structures of the compounds, and especially on the nature of the substituent on C3 of phenylalanine.     

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。     

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.