反相液相色谱中动力学因素对肽谱影响规律研究

研究了用反相色谱模式, 在不同流动相流速条件下所得到的细胞色素C的肽谱图. 发现在低流速时, 保留弱的肽谱峰增多, 而在高流速时保留强的肽谱峰增多, 未发现溶质分子质量与溶质相对保留值(RRT)之间存在有特定的变化关系. 然而却发现了两种变化规律, 即溶质相对保留值(RRT)与流动相流速之间的双对数线性关系(1) log RRT＝a＋blog ν, 及所得该二线性参数, a与b之间的线性关系(2) a＝c＋db. 预计该结果可能会在液相色谱指纹图谱研究和蛋白质组学中分离低丰度蛋白时有潜在的应用价值.     

论电荷转移相互作用对色谱过程的影响

]本文从溶质分子间的电荷转移相互作用,讨论了溶质浓度对色谱过程的影响。由于溶质分子间的相互作用,在一定的浓度范围内改变了固定相的表面吸附状态,改变色谱分离效果,两相邻色谱峰的分辨率随溶质浓度而变化。文中以液体色谱为例,着重从理论上进行阐述,力图得出一些清新的概念。这些概念同时也适合于气相色谱,只不过在方程式的表达上略有不同。     

《毛细管电色谱理论基础》

毛细管电色谱作为一种新型微分离分析技术,其分离过程具有多种机理协同作用的特征。对于毛细管电色谱的理论研究不仅要考虑系统的电属性,还要兼顾溶质的两相分配特征。该书系统地阐述了毛细管电色谱的基本理论,讨论了分离过程中影响峰展宽的因素及其规律。基于作者发展的弛豫理论和唯象的输运过程处理方法,阐述了毛细管电色谱中的动力学和热力学问题,分别就不同的分离模式的选择性规律和柱内富集理论与技术、梯度洗脱的溶质输运特征加以说明。该书可作为从事色谱及毛细管电泳、毛细管电色谱理论及应用研究的科技人员和分析化学专业研究生的…     

《毛细管电色谱理论基础》

毛细管电色谱作为一种新型微分离分析技术,其分离过程具有多种机理协同作用的特征。对于毛细管电色谱的理论研究不仅要考虑系统的电属性,还要兼顾溶质的两相分配特征。该书系统地阐述了毛细管电色谱的基本理论,讨论了分离过程中影响峰展宽的因素及其规律。基于作者发展的弛豫理论和唯象的输运过程处理方法,阐述了毛细管电色谱中的动力学和热力学问题,分别就不同的分离模式的选择性规律和柱内富集理论与技术、梯度洗脱的溶质输运特征加以说明。该书可作为从事色谱及毛细管电泳、毛细管电色谱理论及应用研究的科技人员和分析化学专业研究生的…     

径向色谱中溶质的输运特征

基于溶质在径向色谱柱内输运的质量平衡方程, 在线性分配条件下, 得到了描述分离柱效和流出曲线形状各参数的理论表达式, 也对柱效和流出曲线对称性的变化趋势加以系统讨论. 结果表明: 径向色谱中, 柱效与体积流速之间的关系与轴向色谱中柱效与流动相线速度的关系在趋势上相同; 在较高流速下运行时, 径向色谱仍可以得到高柱效. 随着溶质容量因子、进样时间的增加, 柱效单调降低. 柱直径和柱长对柱效的影响存在交叉, 设计半径较大而长度较短的色谱柱将更有利于提高分离柱效. 径向色谱适宜于大分子样品的稳定分离方法建立, 也预示其对于蛋白、DNA等样品的制备分离具有明显优势.     

磷脂微乳电动色谱的定量结构保留关系研究

以大豆磷脂为主要的表面活性剂,制备适合毛细管电动色谱使用的不同构成比的微乳体系, 应用溶剂化参数模型研究了中性溶质在其中的定量结构保留关系.使用动态涂层毛细管, 以二甲基亚砜和十二烷基苯分别作为电渗流和微乳液滴迁移的标记物, 测定了26个具有不同结构小分子中性化合物在17种微乳电动色谱体系下的保留因子, 建立了线性溶剂化能量关系(LSER)方程.通过比较两体系的LSER方程系数比较体系相似性.结果表明, 本研究建立的磷脂微乳电动色谱体系在线性溶剂化特征上和其它构成的微乳电动色谱体系相似.对溶质保留贡献较大的是溶质体积和有效氢键碱度, 油相种类及浓度对溶质的保留选择性无明显影响.     

小鼠血清IgG的蛋白G灌注亲和色谱行为的研究

通过实验考察了小鼠血清ＩｇＧ的蛋白Ｇ灌注亲和色谱行为,虽然未发现非特异性吸附,但在通常情况下对ＩｇＧ存在不可逆性吸附。洗脱液组成及ｐＨ的不同决定ＩｇＧ在灌注亲和色谱柱上具有不同的解离常数ＫＤ,产生不同的色谱行为。流动相的流速对ＩｇＧ与蛋白Ｇ的结合／解离动力学过程产生一定的影响。结果表明,对于小鼠血清中的ＩｇＧ灌注亲和色谱的分离,由于解离速率影响到传质过程,使之在高流速下的分离受到一定的限制。     

多组分液相色谱体系中溶质保留的计量置换模型

本文全面地考虑了液相色谱体系中溶质和溶剂、溶质和固定相,溶剂和固定相分子之间的各种相互作用和不同种类溶剂分子在固定相表面上的竞争吸咐,提出了一个具有四组参数的溶质在液相色谱中的计量置换保留模型。以文献及实验数据对此模型进行了验证。结果表明,对不同的流动相和不同的固定相体系,在多组分全浓度范围内,此模型都能良好地描述实验事实。     

色谱柱分离过程弛豫理论——流出曲线的动力学本质

在分析型线性色谱中,流出曲线一般表现为拖尾的形式,这种现象可以采用多种机理加以解释。模仿动力学弛豫理论的假设条件,认为溶质在柱过程中的迁移以跃迁形式完成,得到了浓度分布曲线的数学表达式。分别探讨跃迁次数、两相间跃迁速率及溶质在流动相中的轴向跃迁对峰形的影响,进一步说明了色谱流出曲线的动力学本质     

《毛细管电色谱理论基础》

毛细管电色谱作为一种新型微分离分析技术，其分离过程具有多种机理协同作用的特征。对于毛细管电色谱的理论研究不仅要考虑系统的电属性，还要兼顾溶质的两相分配特征。该书系统地阐述了毛细管电色谱的基本理论，讨论了分离过程中影响峰展宽的因素及其规律。基于作者发展的弛豫理论和唯象的输运过程处理方法，阐述了毛细管电色谱中的动力学和热力学问题，分别就不同的分离模式的选择性规律和柱内富集理论与技术、梯度洗脱的溶质输运特征加以说明。     

线性参数logI对反相液相色谱中的非极性小分子溶质体系的表征

从理论上阐明了计量置换平衡常数的对数ｌｏｇＫａ对液相色谱中计量置换保留模型的线性参数ｌｏｇＩ起着主导作用。ｌｏｇＩ表示溶质对固定相的亲合势，且具有热力学平衡常数的性质。     

Micellar bile salt mobile phases for the liquid chromatographic separation of routine compounds and optical, geometrical, and structural isomers

Aqueous solutions of bile salts, i.e. sodium cholate (NaC), sodium deoxycholate (NaDC), and sodium taurocholate (NaTC), are characterized and evaluated as reversed-phase liquid chromatographic (RPLC) mobile phases. The separation of the ASTM-recommended RPLC test mix in addition to more than 50 other compounds on a C18 column demonstrates the viability of these bile salts as HPLC mobile phases. The Armstrong-Nome theory was applied and found to adequately describe the partitioning behavior of solutes eluted with these bile salts at low surfactant concentrations. The effect of alcohol additives on chromatographic retention and efficiency was also assessed. Not only are the bile salt molecules rigid and chiral, but they form helical micellar aggregates as well. Consequently, many isomeric compounds can be easily resolved with this mobile phase additive. The base-line resolution of some binaphthyl-type enantiomers with a standard C18 column and the bile salt micellar mobile phases is also demonstrated. In addition, these bile salt mobile phases may be preferable to conventional hydroorganic mobile phase systems for the separation of many classes of routine compounds. A brief prospectus on the future utilization of bile salts in liquid chromatography is presented.     

Enhancement of selectivity in reversed-phase liquid chromatography

In an effort to gain insight into the relationship between stationary phase solvation and selectivity, the use of short- and medium-chained-length alcohols (methanol, n-propanol, n-butanol, and n-pentanol) as mobile phase modifiers in reversed-phase liquid chromatography (RPLC) was investigated to determine their impact on chromatographic selectivity. A wide range of mobile phase compositions was evaluated because of the large effect exerted by solvent strength on selectivity. Employing a set of six vanillin compounds as retention probes, evidence is presented to support the view that an increase in the hydrophobicity of the organic modifier used in RPLC can increase the selectivity of the C18 alkyl bonded phase while simultaneously decreasing the retention time of the eluting solutes. Thus, we are presented with an interesting paradox: higher selectivity and shorter retention times, which can be attributed to changes in either solvent selectivity and/or stationary phase solvation by the organic modifier.     

Chromatographic selectivity triangles

2010 marked the 50th anniversary of the use of selectivity triangles to characterize chromatographic phases. Such plots ultimately identify and quantify the blend of intermolecular interactions that occur between solutes and solvents/phases. The first chromatographic triangle was proposed by Brown and applied to GC stationary phases. Snyder then developed the influential solvent selectivity triangle (SST) based on the gas-liquid partition data of Rohrschneider. The SST was combined with simplex experimental designs to optimize RPLC separations. Subsequent criticisms of the work revolved around the inaccurate predictions that resulted from the SST. These inaccuracies ultimately relate to the inability of the SST to account for the effects of water on the interaction ability of organic solvents. Other criticisms focused on the selection of the three probe solutes (ethanol, dioxane, and nitromethane) that were used to define the apices of the SST. Here, the concerns include the lack of explicit consideration of dispersion interactions and the fact that the three probes do not represent any single intermolecular interaction but rather reflect a blend of intermolecular interactions. The SST approach was modified for NPLC by redefining the triangle apices to reflect the localization, general adsorption, and basicity of NPLC mobile phase modifiers. Because water is generally absent in NPLC, the triangle approach leads to better predictions for NPLC than for RPLC. In subsequent modifications of selectivity triangles, Fu and Khaledi have created a micellar selectivity triangle (MST) based on linear solvation energy relationships (LSERs) and Zhang and Carr have used the Dolan-Snyder hydrophobic subtraction model to create RPLC column selectivity triangles. We end this review by highlighting more recent methods for comparing selectivities and by discussing a new 3D visualization tool for classifying chromatographic systems as having similar or different fundamental energetics of retention and hence having similar or different selectivities.     

Chiral discrimination of dansyl-amino-acid enantiomers on teicoplanin phase: sucrose-perchlorate anion dependence

The chiral recognition mechanism for a series of d,l-dansyl-amino-acids (test solutes) on a teicoplanin stationary phase was investigated in reversed phase liquid chromatography (RPLC). The effect of both a surface tension modifier (sucrose) and a chaotropic agent (perchlorate anion) on the enantiomeric separation was studied by varying their concentration, c, in the mobile phase. The thermodynamic data supported the fact that the sucrose molecule acted only on the hydrophobic part of the interaction teicoplanin/dansyl-amino-acid and not on the specific chiral part. It was demonstrated that the enhancement of the separation factor observed as the perchlorate salt concentration increased in the mobile phase was enthalpically controlled owing to stereoselective bonding interactions. Such behavior was used to optimize the chromatographic conditions for separation of dansyl-amino-acids on teicoplanin.     

Submicellar and micellar reversed-phase liquid chromatographic modes applied to the separation of β-blockers

The behaviour of a reversed-phase liquid chromatographic (RPLC) system (i.e. elution order, resolution and analysis time), used in the analysis of β-blockers with acetonitrile–water mobile phases, changes drastically upon addition of an anionic surfactant (sodium dodecyl sulphate, SDS). Surfactant monomers cover the alkyl-bonded phase in different extent depending on the concentration of both modifiers, in the ranges 1 × 10⁻³–0.15 M SDS and 5–50% acetonitrile. Meanwhile, the surfactant is dissolved in the mobile phase as free monomers, associated in small clusters or forming micelles. Four characteristic RPLC modes are yielded, with transition regions between them: hydro-organic, micellar, and low and high submicellar. The mobile phases in the two latter modes contain a concentration of SDS below or well above the critical micellar concentration (CMC) in water (i.e. 8 × 10⁻³ M), and more than 30% acetonitrile. High submicellar RPLC appeared as the most promising mode, as it allowed full resolution of the β-blockers in practical times, while these were unresolved or highly retained in the other RPLC modes. The strong attraction of the cationic solutes to the anionic SDS makes a direct transfer mechanism between surfactant molecules in the stationary and mobile phases likely.     

两种带有不同间隔臂的环糊精键合固定相保留行为的评价

选取14种模型化合物对两种带有不同间隔臂的环糊精键合固定相(Click Alkyl-CD、Click OEG-CD)进行了反相液相色谱模式下的保留行为评价。通过梯度洗脱条件下保留参数计算方法和CSASS软件,根据3次线性梯度的保留值数据,测出14种溶质分子在两种固定相上的保留参数,在此基础上考察流动相含乙腈浓度与保留因子的关系后发现,Click Alkyl-CD和Click OEG-CD在分离非极性和中等极性化合物时主要基于反相液相色谱模式,而某些化合物(如吲唑)在Click OEG-CD上的保留受多种作用力影响,并不基于反相液相色谱模式。疏水性评价结果表明,反相分离模式下Click Alkyl-CD的保留参数和正辛醇-水分配常数的相关性较好(R=0.7),说明其具有比较强的疏水性;而Click OEG-CD的相关性不高(R＜0.3),说明疏水作用力以外的其他作用力对化合物在反相模式下的保留影响较大。     

Retention mechanisms in micellar liquid chromatography

Micellar liquid chromatography (MLC) is a reversed-phase liquid chromatographic (RPLC) mode with mobile phases containing a surfactant (ionic or non-ionic) above its critical micellar concentration (CMC). In these conditions, the stationary phase is modified with an approximately constant amount of surfactant monomers, and the solubilising capability of the mobile phase is altered by the presence of micelles, giving rise to diverse interactions (hydrophobic, ionic and steric) with major implications in retention and selectivity. From its beginnings in 1980, the technique has evolved up to becoming a real alternative in some instances (and a complement in others) to classical RPLC with hydro-organic mixtures, owing to its peculiar features and unique advantages. This review is aimed to describe the retention mechanisms (i.e. solute interactions with both stationary and mobile phases) in an MLC system, revealed in diverse reports where the retention behaviour of solutes of different nature (ionic or neutral exhibiting a wide range of polarities) has been studied in a variety of conditions (with ionic and non-ionic surfactants, added salt and organic solvent, and varying pH). The theory is supported by several mechanistic models that describe satisfactorily the retention behaviour, and allow the measurement of the strength of solute-stationary phase and solute-micelle interactions. Suppression of silanol activity, steric effects in the packing pores, anti-binding behaviour, retention of ionisable compounds, compensating effect on polarity differences among solutes, and the contribution of the solvation parameter model to elucidate the interactions in MLC, are commented.