新型程序涂渍色谱柱程序效应的研究

新型程序涂渍色谱柱程序效应的研究许鸿生，洪辉（湘潭大学化学系，湘潭，４１１１０５）关键词新型程序柱，程序效应，气相色谱关于程序涂渍色谱柱的问题，国内外研究指数函数程序柱的较多［１～３］，色谱柱涂渍结构改变后，组分的保留行为及柱效能都发生较大变化．作者...     

气相色谱柱对分析时间最佳程序化的研究

本文从理论和实验两方面探讨了指数程序涂渍色谱柱对分析时间的最优程序变化,实验结果和理论计算基本相符。同时考察了程序涂渍色谱柱对不同液载比的应用范围及其段数对程序化的影响。     

程序涂渍气相色谱柱的应用——微量有机物的定量分析

关于程序涂渍气相色谱柱理论研究已做了一系列的工作,其应用也已经引起了色谱工作者的关注。由于程序涂渍色谱柱具有分析速度快、分离效能高的特点,很适合于有机物中微量杂质的测定,尤其微量杂质在主组分之后出峰的情况下更能显示出程序柱的优越性。     

程序涂渍柱保留时间“程序效应”的研究

本文对程序涂渍色谱柱保留时间的“程序效应”做了进一步探讨,建立了“程序效应”概念,给出了函数关系式及色谱柱结构的计算公式,编制了计算机程序。     

单壁碳纳米管+SE-30毛细管柱的制备研究及对多种物质的拆分

使用单壁碳纳米管(SWNTs)作气相色谱的固定相, 并用静态涂渍法在单壁碳纳米管内壁涂渍浓度不同的SE-30固定液. 为考察固定液浓度不同的几根毛细管柱的柱性能, 对多种物质进行了拆分, 并将该拆分结构与直接涂渍SE-30柱的毛细管柱性能进行对照. 实验结果表明: 键合了SWNTS再涂渍SE-30的毛细管柱较之直接涂渍SE-30的毛细管柱拆分效果有所改进, 但存在一定的拖尾现象. 此外, 前者对气体有较好的拆分效果, 且其效果随SE-30浓度按一定规律变化. 从分离性能来看, 键合了SWNTS再涂渍SE-30的固定相对气体的分离具有较好的效果.     

超动态法快速制备毛细管色谱柱的研究

用超动态法快速制出了几种非极性毛细管柱,柱效、涂渍效率分别为3000～4500理论塔板/m和65～85%。研究了超动态法中涂渍压力、涂渍液浓度与容量因子的关系;考察了制柱重复性和液膜厚度均匀性;给出了涂渍一般口径和试涂大口径厚液膜毛细管柱的部分结果。     

指数程序薄涂色谱柱的性能及用于己二酸的分析

在气相色谱分析中,有关程序涂渍色谱柱的研究已有报道,这种色谱柱较适合于厚涂柱的分析。本文所研制的指数程序薄涂色谱柱及分析应用,尚未见报道。该色谱柱是将一根色谱柱分成几段,将每段的固定液涂渍量按指数函数y=m~i(i=1,2,3)变化,而每段固定液量都不超过1％,色谱柱选定为1m。由于固定液量少,且采用指数程序涂渍,因此,色谱操作柱温可较低,分离效能较高,组分的保留时间短,很适合较高沸点、易分解化合物的直接快速分析。 此色谱柱应用于实际样品中己二酸(沸点为330℃,近沸点时分解)的分析,己二酸于160℃下出峰快,保留时间短,峰形较对称,容易定量。其最小检测量为0.80μg,回收率为101.5％,相对标准偏差为±5.9％。 实验部分 (一)主要仪器与色谱条件 1.仪器 上海103气相色谱仪,热导池检测器,岛津C-R3A数据处理机。 2.色谱条件 色谱柱为1m×0.3mm不锈钢柱;固定液为QF-1按0.34％、0.49％、0.7％涂渍;载体为硅烷化玻璃微球(80～100目);载气(H_2)流速40ml/min;桥流150mA;汽化温度172℃;柱温160℃;检测温度170℃。 (二)试剂     

采用易挥发溶剂,静置、自然干燥法涂渍气相色谱固定液

在涂渍气相色谱固定液时,选用易挥发,低粘度溶剂(如正己烷,丙酮等)．担体与溶剂按一定比例混合,溶剂恰好湿润担体,无多余溶剂,涂渍过程不需搅拌、加热等程序,不需旋转蒸发器、水浴、红外灯等设备．此方法具有操作简单,涂渍快速,操作人员中毒少,担体破碎少等优点,而且保证固定液涂渍均匀．本文给出了常用固定液所用易挥发溶剂及常用担体在用本方法涂渍时固定液与溶剂的比例．     

超动态法快速制备毛细管色谱柱研究

涂渍毛细管柱常用的方法有静态法和动态法。恒温下自由蒸发溶剂和以液化的气体作固定液溶剂的静态法虽改进了静态法的涂渍速度,涂渍条件却要求苛刻。最近V.G.Berezkin和A.A.Korolev报道了超动态法制柱的方法,它比经典动态法有明显的改进。例如具有制柱速度快、柱效高、方法简便和重复性好等优点。本文用甲基乙烯基聚硅氧烷固定液     

C_1～C_8醇气相色谱分离固定相及操作条件的选择

前言低级脂肪族一元醇的气相色谱分离和测定,国外报导较多。本文研究了C_1～C_8醇类在10种色谱柱上的保留行为,并以新戊二醇己二酸聚酯柱为例,进行了固定涂渍量,担体,柱温,载气和柱内径的选择条件实验。在选择条件下,可显著提高分析速度,不用程序升温控制,     

Prediction of elution bandwidth for purine compounds by a retention model in reversed-phase HPLC with linear-gradient elution

In reversed-phase liquid chromatography, the retention mechanism of solute has been studied under linearly programmed gradient mobile-phase conditions. The separation of a mixture of four purine compounds (purine, theobromine, theophylline, and caffeine) was considered as a practical case in two binary mobile phase systems, water/methanol and water/acetonitrile. The retention model which describes how the retention factor is related to the mobile-phase composition has been developed in various mathematical forms to predict the retention time in both linear and gradient elutions. For a pulse injection of sample, two important factors, the retention time and the bandwidth of solute, might be computable to predict the elution profiles estimated by the distribution function, such as the Gaussian distribution function. In this work, a prediction method based on the analogue of the retention model was proposed to calculate the bandwidth in linear gradient elutions. Band broadening was caused by the different migration velocities of the front and rear ends of the solute band in a chromatographic column. Therefore, the migration behaviors of the front and rear ends of the solute band were explained with the same retention model which had been used to predict the retention time of solute. For the well retained solutes, theophylline and caffeine, the predicted bandwidth and experimentally obtained bandwidth showed good agreement in both isocratic and gradient elutions.     

Oil-In-Water Microemulsion LC Determination of Pharmaceuticals Using Gradient Elution

Efficient and novel oil-in-water microemulsion HPLC (MELC) separations of a range of solutes have been performed on conventional reversed-phase HPLC columns using gradient elution. This work follows previous successful separations using isocratic oil-in-water MELC [1]. It was found that by changing certain variables, peak-peak resolution, separation selectivity, efficiency and solute retention could be manipulated. The method was compatible with very low UV detection wavelengths. A robust separation method was developed for the quantitative analysis of 2 steroids in a combination-inhaled product for asthma. The method offered similar chromatography and run time when compared with conventional HPLC modes, thus demonstrating its potential for routine use. Stability-indicating methods were developed to separate synthetic and degradative impurities from the main component peaks in 4 pharmaceutical products. The methods offered quicker analysis times and equivalent selectivity to conventional HPLC modes. In developing the separations the effect on the chromatography of varying the operating parameters was studied.     

A Study of Retention Time Gradient Effect of Gradientally Loaded Columns

In this work, the "retention time gradient effect" of gradient GC columns is intensively studied to establish some equations and formulas for structure calculation of chromatographic columns. In addition, the relevant computer programs are designed.     

Contributions to reversed-phase column selectivity. II. Cation exchange

The contribution of cation exchange to solute retention for type-B alkylsilica columns (made from high-purity silica) has been examined in terms of the hydrophobic-subtraction (H-S) model of reversed-phase column selectivity. The relative importance of cation exchange in the separation of ionized bases by reversed-phase chromatography (RPC) varies with (a) column acidity (values of the column cation-exchange capacity C), (b) mobile-phase pH and buffer concentration, and (c) the nature of the buffer cation. The effects of each of these separation variables on cation retention were examined. The contribution of cation exchange (and other ionic interactions) to solute retention is represented in the H-S model by properties of the solute (κ') and column (C), respectively. Values of κ' for 87 solutes have been examined as a function of solute molecular structure, and values of C for 167 type-B alkylsilica columns have been related to various column properties: ligand length (e.g., C(8) vs. C(18)) and concentration (μmol/m(2)), pore diameter (nm), and end-capping. These results contribute to a more detailed picture of the retention of cationic solutes in RPC as a function of separation conditions. While previous work suggests that the ionization of type-B alkylsilica columns is generally negligible with mobile-phase pH<7 (as a result of which cation exchange then becomes insignificant), the present study provides evidence for cation exchange (and presumably silanol ionization) at a pH as low as 3 for most columns.     

Retention time and effective separation factor in series-coupled columns with different stationary phases

Basic expressions are derived for both the retention time and the effective separation factor in serially coupled GC columns. The retention time is determined by two main parameters. The first is the fractional time spent by an unretarded solute in each column which, in turn, is determined by the relative column lengths and flow velocities through each column. The second parameter is the relative mass distribution coefficient of a particular solute in each column; a variable that can be adjusted by changing the relative temperatures of the columns. The expression for the effective separation factor relates the measured separation factor for the series combination to the separation factors on the individual columns, the fractional time spent by an unretarded peak in each column, as well as the relative values of the mass distribution coefficients of a particular solute on the different columns.     

Capillary electrochromatography with monolithic silica column: I. Preparation of silica monoliths having surface-bound octadecyl moieties and their chromatographic characterization and applications to the separation of neutral and charged species

Monolithic silica columns with surface-bound octadecyl (C18) moieties have been prepared by a sol-gel process in 100 microm ID fused-silica capillaries for reversed-phase capillary electrochromatography of neutral and charged species. The reaction conditions for the preparation of the C18-silica monoliths were optimized for maximum surface coverage with octadecyl moieties in order to maximize retention and selectivity toward neutral and charged solutes with a sufficiently strong electroosmotic flow (> 2 mm/s) to yield rapid analysis time. Furthermore, the effect of the pore-tailoring process on the silica monoliths was performed over a wide range of treatment time with 0.010 M ammonium hydroxide solution in order to determine the optimum time and conditions that yield mesopores of narrow pore size distribution that result in high separation efficiency. Under optimum column fabrication conditions and optimum mobile phase composition and flow velocity, the average separation efficiency reached 160 000 plates/m, a value comparable to that obtained on columns packed with 3 microm C18-silica particles with the advantages of high permeability and virtually no bubble formation. The optimized monolithic C18-silica columns were evaluated for their retention properties toward neutral and charged analytes over a wide range of mobile phase compositions. A series of dimensionless retention parameters were evaluated and correlated to solute polarity and electromigration property. A dimensionless mobility modulus was introduced to describe charged solute migration and interaction behavior with the monolithic C18-silica in a counterflow regime during capillary electrochromatography (CEC )separations. The mobility moduli correlated well with the solute hydrophobic character and its charge-to-mass ratio.     

梯度液相色谱保留时间公式在梯形梯度洗脱研究中的应用

根据前期得到的梯度液相色谱保留时间计算公式,在不指定溶剂强度模型形式的前提下,探讨了梯形梯度洗脱的一些特点。对于溶质在梯形梯度坡度上流出时的情形,推导得到溶质流出色谱柱所对应的流动相组成(φ_R)随梯度斜率(B)变化的表达式。该公式表明,在该情形中φ_R将会随着B值的增加而增加。对于溶质在梯形梯度最后一个等度区间流出时的情形,如果初始和终止流动相组成保持不变而仅有梯度的斜率发生变化时,从理论上证明了溶质保留时间(t_R)与梯度斜率的倒数(1/B)之间呈线性关系。实验中以C18色谱柱为固定相,甲醇-水为流动相,联苯为样品,测定了不同流动相组成以及梯形梯度条件下的保留时间,所得到的实验值与理论值吻合,从而验证了理论方法的正确性。     

Deformation of gradient shape as a result of preferential adsorption of solvents in mixed mobile phases

Gradient elution has been studied in typical normal and reversed-phase systems. Deformations of gradient profiles have been evidenced as a result of preferential adsorption of modifiers of the mobile phase. This phenomenon was pronounced in the normal-phase system, for which gradient profiles deviated significantly from those programmed. This influenced the retention and shapes of band profiles of the eluting solute. Hence, in order to predict gradient propagation correctly the adsorption equilibrium of modifiers has been quantified. Moreover, at low modifier content, deformations of band profiles of the solute has been registered as a result of the competitive adsorption in the system solute-modifier. This effect has been predicted by a competitive adsorption model. For the reversed-phase systems the influence of the modifier adsorption on gradient propagation was insignificant for typical mobile phases investigated. Therefore, the work has been focused on gradient predictions in the normal-phase system.     

The effects of the column pressure drop on retention and efficiency in packed and open tubular supercritical fluid chromatography

The effects of the pressure drop across the column on retention and efficiency in SFC have been studied. Numerical methods are described which enable the prediction of hold-up time and pressure drop in both packed and open tubular columns. Predictions of both hold-up time and pressure drop are in good agreement with experimental data. The density gradient along the column can be calculated using the numerical methods and a procedure is described which enables the calculation of the overall capacity factors of the solutes from the density profile in the column. Significant variations of the capacity factor are observed along the column. The effect of the density gradient along the column on local diffusivity and dispersion is studied. The column efficiency in systems with significant pressure drops is affected by changes in: the linear velocity of the mobile phase; the diffusion coefficients; and the capacity factors of the solutes along the column. The overall efficiency of the chromatographic system can be calculated if, as is the case for open tubular columns, adequate plate height equations are available.