共查询到20条相似文献,搜索用时 15 毫秒
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The solvation parameter model is used to characterize the separation properties of the polar stationary phases EC-Wax and PAG with a poly(ethylene oxide) backbone (substituted with propylene oxide in the case of PAG) and the cyanopropyl-substituted polysilphenylene-siloxane stationary phase BPX90 at five equally spaced temperatures between 60 and 140 degrees C. The separation characteristics of these stationary phases are compared to four PEG and two poly(cyanopropylsiloxane) stationary phases (HP-20M, HP-Innowax, SolGel-Wax, DB-WAXetr, HP-88, and SP-2340) characterized in the same way. The database of system constants for these polar stationary phases is used to provide insight into the separation mechanism for fatty acid methyl esters and to determine selectivity differences that can be expected for generically similar stationary phase types. The discussion is not structured to indicate which stationary phase should be used for a particular separation but to provide a general framework to demonstrate the relationship between the retention mechanism and stationary phase chemistry. 相似文献
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J. E. Knox H. P. Hratchian N. Trease J. Struble H. B. Schlegel H. L. S. Holmes 《Chromatographia》2004,59(5-6):329-334
The utility of electronic structure methods for studying and predicting interactions in gas chromatography is explored using a simplified model of polyethylene glycol with a homologous series of normal alcohols. Relative interaction energies were determined using stabilization energies taken at stationary points on the analyte/stationary phase potential energy surfaces using semi-empirical, ab initio, and density functional theory. Second order Mø
øller-Plesset electronic structure method produced good qualitative agreement with experiment, clearly indicating the need for a model that includes weak dispersion forces. 相似文献
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The solvation parameter model was applied in the development of a method for the analysis of residual solvents in pharmaceuticals. The interactions between organic solvents and six different stationary phases were studied using gas chromatography. The retention times of the organic solvents on these columns could be predicted under isothermal or temperature-programmed conditions using the established solvation parameter models. The predicted retention times helped in column selection and in optimizing chromatographic conditions during method development, and will form the basis for the development of a computer-aided method. 相似文献
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The problem of the calculation and interpretation of the net retention volume with a real gas as carrier is revisited. The properties of the carrier are described by a first order virial equation of state. The net retention volume of a solute is related to the mean flow rate of the carrier, therefore determination of the mean flow rate of a real gas carrier is reviewed. It is shown that the mean flow rate cannot be calculated from the mean column pressure. With a real gas carrier the local capacity factor depends on the local pressure of the real gas. The basic relationship between the net retention volume and the function describing this pressure dependence is also reviewed. Precise formulae as well as practical approximations are presented for the calculation of the mean flow rate, of the mean column pressure, and of a representative pressure related to the mean capacity factor. 相似文献
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建立了气相色谱过程的动态数学模型,给出了模型的实用算法,并据此对各种操作条件下的色谱流出曲线进行了动态模拟计算。模拟计算结果表明该模型是有效的,能够用于各种程序控制的色谱过程,可得到色谱分离的优化条件。 相似文献
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This article provides a summary of the development of ionic liquids as stationary phases for gas chromatography beginning with early work on packed columns that established details of the retention mechanism and established working methods to characterize selectivity differences compared with molecular stationary phases through the modern development of multi-centered cation and cross-linked ionic liquids for high-temperature applications in capillary gas chromatography. Since there are many reviews on ionic liquids dealing with all aspects of their chemical and physical properties, the emphasis in this article is placed on the role of gas chromatography played in the design of ionic liquids of low melting point, high thermal stability, high viscosity, and variable selectivity for separations. Ionic liquids provide unprecedented opportunities for extending the selectivity range and temperature-operating range of columns for gas chromatography, an area of separation science that has otherwise been almost stagnant for over a decade. 相似文献
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Retention properties of a cyanopropylsiloxane-bonded silica-based sorbent for solid-phase extraction
The characteristic kinetic and retention properties of a silica-based cyanopropylsiloxane-bonded sorbent for solid-phase extraction are described. Abraham′s solvation parameter model is used to characterize the contribution of individual intermolecular interactions to retention under liquid chromatographic and sample processing conditions with aqueous methanol mixtures as the mobile phase. The main features governing retention by the sorbent are the solute's size and hydrogen-bond basicity; interactions of a dipole type are not significant when aqueous methanol solutions are employed as the mobile phase. Compared to typical silica-based octadecylsioxane-bonded sorbents the greater difficulty of forming a cavity in the solvated cyanopropylsiloxane-bonded sorbent more than offsets the more favorable dipole-type and solute hydrogenbond base interactions of the cyanopropylsiloxane-bonded sorbent. It is shown that there are no practical circumstances for which a cyanopropylsiloxane-bonded sorbent would be more useful than a typical ODS sorbent for the isolation of organic non-electrolytes from water by solid-phase extraction. 相似文献
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Summary A global LSER model that relates HPLC retention to mobile phase composition and pH is tested for a varied group of solutes,
both neutral and ionizable, in a polymeric column and methanol-water mobile phases. It is compared to the local LSER model
developed only for a given mobile phase, i.e., a fixed organic modifier content, and to the global LSER model set only for
neutral solutes. The global LSER model for neutral and ionizable solutes requires a few supplementary parameters over the
other models tested, but it accounts for retention under any experimental conditions for a given column and methanol-water
mobile phases, describing properly the interactions established in the HPLC system (hydrophobicity, hydrogen-bond acidity
and basicity, dipolarity/polarizability…).
This paper is number 13 of a series with the same general title: “Retention of Ionizable Compounds on HPLC” published in various
journals. 相似文献
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二茂铁衍生物在四氢呋喃-甲醇-水三元溶剂系统中的保留符合Kowalska所提出的物理化学保留模型1。但由于模型1没有考虑到化学计量问题,故其结果不够精确。本文在模型1中引入粘度系数来定量表示化学计量关系,得到明显优于模型1的模型2。鉴于HPLC系统中常以logK’表示保留值,本文以logK代替模型1,2中的Rf值,简化了计算。 相似文献
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BIANLiu-jiao YANGXiao-yan 《高等学校化学研究》2004,20(3):281-284
In consideration of the adsorption of solvent, diluent and solute molecules on the surface of a stationaryphase, a new equation for solute retention in liquid chromatography is presented. This equation includesthree parameters: the displacement equilibrium constant (Ksd) between the solvent and diluent molecules onthe surface of the stationary phase, the total number(N) of the solvent and diluent molecules released fromthe stationary phase after one solute molecule being adsorbed, and the parameter (I) related to the thermody-namic equilibrium constant for the solute adsorption on the stationary phase. Over the whole concentrationrange of the solvent in the mobile phase, the experimental retention data can be well described by this equa-tion, parameters K~, N and I can be obtained by the regression analysis of the experimental retention data,and consequently the number of the solvent and the diluent molecules displaced by one solute molecule fromthe stationary phase can also be derived at different solvent concentrations in the mobile phase, 相似文献
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毒鼠强的气相色谱法快速检验 总被引:5,自引:0,他引:5
介绍了采用气相色谱法测定生物检材中的毒鼠强含量的方法。采用氮磷检测器 ,使用HP-1,HP-5石英毛细管柱 ,检出限可达1ng。用苯作为提取溶剂 ,胃组织中毒鼠强回收率为82.8%。方法简便、快速、准确。 相似文献
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The selectivity of a compilation of single, mixed, and modified EKC pseudostationary phases, described in the literature and characterized through the solvation parameter model, is analyzed. Not only have micellar systems of different nature been included but also microemulsions, polymeric, and liposomial phases. In order to compare the systems, a principal component analysis of the coefficients of the solvation equation is performed. From this analysis, direct information of the system properties, differences in selectivity, as well as evidence of lack of accuracy in some system characterizations are obtained. These results become a very useful tool to perform separations with mixtures of surfactants, since it is possible to know which mixtures will provide a greater selectivity variation by changing only the composition of the pseudostationary phases. Furthermore, the variation of the selectivity of some mixtures, as well as the effect of the addition of organic solvents on selectivity, is also discussed. 相似文献
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通过气相色谱、红外光谱分析和量子化学计算,探究溶于二甲基亚砜(DMSO)中乙酸保留时间发生波动的原因。 结果显示,乙酸保留时间变化与DMSO体积等量递增呈线性关系,R2=0.99301;根据红外光谱分析得出,DMSO和乙酸之间生成了氢键,以DMSO-乙酸分子的形式通过色谱柱;根据Gaussian09程序计算结果,DMSO电子密度大的部分给予电子,与乙酸之间形成了氢键,而DMSO电子密度小的部分容易获得电子与具有强偶极矩的色谱柱固定液聚乙二醇产生作用力,吸附在固定液上。因此,在上述一系列复杂的分子间作用力的共同影响下,乙酸保留时间发生了波动,且随着溶剂DMSO体积比增加,乙酸保留时间不断延长。 相似文献