A simple frontal analysis equation to determine the adsorption parameters of solute molecules on different adsorbents was presented. It gives the relationship between the average breakthrough time and the feed solute ...A simple frontal analysis equation to determine the adsorption parameters of solute molecules on different adsorbents was presented. It gives the relationship between the average breakthrough time and the feed solute concentration, and by using its linear form, two important parameters, the thermodynamic equilibrium constant KSL for solute adsorption on the surface of adsorbent and the number nt of total adsorption sites distributed on the surface of adsorbent, can be simultaneously determined. The frontal analyses for some aromatic hydrocarbons on RP-C18 reversed-phase medium, and some protein molecules on RP-C18 reversed-phase, WCX-1 cation-exchange, PEG-400 hydrophobic and Chelating Sepharose Fast-flow separately chelated with Zn^2＋ or Cu^2＋ media, were separately carried out to test this equation and their adsorption parameters KSL and nt were separately obtained. The results show that all these frontal analysis data can be well described by this frontal analysis equation. For all of these frontal analysis systems, their parameters nt can separately approximately keep constant and they are independent of solute molecules used, while their parameters KSL are dependent upon both of the media packed in frontal analysis column and the solute molecules used.展开更多
Adsorption isotherm is the most fundamental information related to chromatography. To calculate the parameters of Langmuir ad-sorption isotherm of thymidine, frontal analysis (FA) and elution-curve method (ECM) were a...Adsorption isotherm is the most fundamental information related to chromatography. To calculate the parameters of Langmuir ad-sorption isotherm of thymidine, frontal analysis (FA) and elution-curve method (ECM) were adopted in reversed-phase high performance liguid chromatography (RP-HPLC). In FA, the concentration of stationary phase was measured from the elution curves and the isotherm was deter-mined by regression analysis, while the parameters by ECM were obtained by parameter optimization. The adsorption isotherms of thymidine from the two methods were very similar. The superiority of ECM over FA was that the consumption of sample was less and only one or two in-jections of sample were required.展开更多
With frontal analysis (FA), the dependence of adsorption isotherms of insulin on the composition of mobile phase in reversed phase liquid chromatography (RPLC) has been investigated. This is also a good example to em...With frontal analysis (FA), the dependence of adsorption isotherms of insulin on the composition of mobile phase in reversed phase liquid chromatography (RPLC) has been investigated. This is also a good example to employ the stoichiometric displacement theory (SDT) for investigating solute adsorption in physical chemistry. Six kinds of mobile phase in RPLC were employed to study the effects on the elution curves and adsorption isotherms of insulin. The key points of this paper are: (1) The stability of insulin due to delay time after preparing, the organic solvent concentration, the kind and the concentration of ion pairing agent in mobile phase were found to affect both elution curve and adsorption isotherm very seriously. (2) To obtain a valid and comparable result, the composition of the mobile phase employed in FA must be as same as possible to that in usual RPLC of either analytical scale or preparative purpose. (3) Langmuir Equation and the SDT were employed to imitate these obtained adsorption isotherms. The expression for solute adsorption from solution of the SDT was found to have a better elucidation to the insulin adsorption from mobile phase in RPLC.展开更多
In previous paper a new adsorption isotherm which relates the amount of solute absorbed to the solvent concentration is proposed and simplified, and it only can be used at lower solute concentration. In this article t...In previous paper a new adsorption isotherm which relates the amount of solute absorbed to the solvent concentration is proposed and simplified, and it only can be used at lower solute concentration. In this article the scope of the new adsorption isotherm is extended and the expressions with three and four parameters are obtained. The equations with multi parameters are valid when the adsorbed amounts are larger and show non linear logarithmic relationships. Tests with a homologue of aromatic alcohols by frontal analysis in reversed phase liquid chromatography demonstrate that the experimental results fit those equations well. In addition, the predicted values by the multi parameters were found to fit the experimental values well also. The parameters have physical meaning only for the two parameter equation for the aromatic alcohols.展开更多
The determination of isotherm and prediction of retention values are the basis of the optimization of separation conditions of preparative chromatography.In this paper,the isotherms of ginsenoside Rg1 and Re from Pana...The determination of isotherm and prediction of retention values are the basis of the optimization of separation conditions of preparative chromatography.In this paper,the isotherms of ginsenoside Rg1 and Re from Panax ginseng were studied.Ginsenoside Rg1 and Re were prepared by chromatography column from Panax ginseng raw material,and the isotherms of ginsenoside Rg1 and Re were determined by frontal analysis(FA) on spherical C18 solid phase.The adsorption parameters G and b were set based on the competitive Langmuir model.In the mean time,the retention time of ginsenoside Re was obtained with the results of nonlinear chromatography theory.The calculated retention time were compared with that of experimental results with average relative error 3.68%.Additionally,some problems related to fitting based on the competitive Langmuir model were found and discussed.展开更多
With four kinds of mobile phases, methanol water, ethanol water, 2 propanol and acetonitrile water (all containing 0 1% triflu roacetic acid), the displacement between solute and solvent in RPLC was proved to be...With four kinds of mobile phases, methanol water, ethanol water, 2 propanol and acetonitrile water (all containing 0 1% triflu roacetic acid), the displacement between solute and solvent in RPLC was proved to be universal in frontal analysis (FA). Based on the measured Z value in usual RPLC to be a constant and the quantitative determination of methanol increment in mobile phase in FA, the stoichiometric displacement (SD) between insulin and methanol was directly proved by the experiment. The SD was also proved to occur only on about the one fourth of the maximum amount of adsorbed methanol in the bonded phase layer (BPL) without any dynamic problem of mass transfer, while in FA, the SD firstly occurs on the surface of the BPL and then gradually sinks into the deeper sites companied with a dynamic problem. Although the displaced solvent by the same solute is less in the former case, the SD is independent of how deep of the solute enters the BPL. In addition, the adsorbed amount of solute on an adsorbent not only depends on the numbers of the adsorbed layer on the adsorbent surface, but also on the extent of the complete removal of the displaceable solvent in the BPL. The physical fundamental of the SD and the methodology for investigation were also discussed.展开更多
基金Project supported by the Natural Science Foundation of Shaanxi Province （No. 2001K10-G3-3）.
文摘A simple frontal analysis equation to determine the adsorption parameters of solute molecules on different adsorbents was presented. It gives the relationship between the average breakthrough time and the feed solute concentration, and by using its linear form, two important parameters, the thermodynamic equilibrium constant KSL for solute adsorption on the surface of adsorbent and the number nt of total adsorption sites distributed on the surface of adsorbent, can be simultaneously determined. The frontal analyses for some aromatic hydrocarbons on RP-C18 reversed-phase medium, and some protein molecules on RP-C18 reversed-phase, WCX-1 cation-exchange, PEG-400 hydrophobic and Chelating Sepharose Fast-flow separately chelated with Zn^2＋ or Cu^2＋ media, were separately carried out to test this equation and their adsorption parameters KSL and nt were separately obtained. The results show that all these frontal analysis data can be well described by this frontal analysis equation. For all of these frontal analysis systems, their parameters nt can separately approximately keep constant and they are independent of solute molecules used, while their parameters KSL are dependent upon both of the media packed in frontal analysis column and the solute molecules used.
文摘Adsorption isotherm is the most fundamental information related to chromatography. To calculate the parameters of Langmuir ad-sorption isotherm of thymidine, frontal analysis (FA) and elution-curve method (ECM) were adopted in reversed-phase high performance liguid chromatography (RP-HPLC). In FA, the concentration of stationary phase was measured from the elution curves and the isotherm was deter-mined by regression analysis, while the parameters by ECM were obtained by parameter optimization. The adsorption isotherms of thymidine from the two methods were very similar. The superiority of ECM over FA was that the consumption of sample was less and only one or two in-jections of sample were required.
文摘With frontal analysis (FA), the dependence of adsorption isotherms of insulin on the composition of mobile phase in reversed phase liquid chromatography (RPLC) has been investigated. This is also a good example to employ the stoichiometric displacement theory (SDT) for investigating solute adsorption in physical chemistry. Six kinds of mobile phase in RPLC were employed to study the effects on the elution curves and adsorption isotherms of insulin. The key points of this paper are: (1) The stability of insulin due to delay time after preparing, the organic solvent concentration, the kind and the concentration of ion pairing agent in mobile phase were found to affect both elution curve and adsorption isotherm very seriously. (2) To obtain a valid and comparable result, the composition of the mobile phase employed in FA must be as same as possible to that in usual RPLC of either analytical scale or preparative purpose. (3) Langmuir Equation and the SDT were employed to imitate these obtained adsorption isotherms. The expression for solute adsorption from solution of the SDT was found to have a better elucidation to the insulin adsorption from mobile phase in RPLC.
基金ProjectsupportedbytheNationalNaturalScienceFoundationofChina (No .2 0 175 0 16)
文摘In previous paper a new adsorption isotherm which relates the amount of solute absorbed to the solvent concentration is proposed and simplified, and it only can be used at lower solute concentration. In this article the scope of the new adsorption isotherm is extended and the expressions with three and four parameters are obtained. The equations with multi parameters are valid when the adsorbed amounts are larger and show non linear logarithmic relationships. Tests with a homologue of aromatic alcohols by frontal analysis in reversed phase liquid chromatography demonstrate that the experimental results fit those equations well. In addition, the predicted values by the multi parameters were found to fit the experimental values well also. The parameters have physical meaning only for the two parameter equation for the aromatic alcohols.
文摘The determination of isotherm and prediction of retention values are the basis of the optimization of separation conditions of preparative chromatography.In this paper,the isotherms of ginsenoside Rg1 and Re from Panax ginseng were studied.Ginsenoside Rg1 and Re were prepared by chromatography column from Panax ginseng raw material,and the isotherms of ginsenoside Rg1 and Re were determined by frontal analysis(FA) on spherical C18 solid phase.The adsorption parameters G and b were set based on the competitive Langmuir model.In the mean time,the retention time of ginsenoside Re was obtained with the results of nonlinear chromatography theory.The calculated retention time were compared with that of experimental results with average relative error 3.68%.Additionally,some problems related to fitting based on the competitive Langmuir model were found and discussed.
文摘With four kinds of mobile phases, methanol water, ethanol water, 2 propanol and acetonitrile water (all containing 0 1% triflu roacetic acid), the displacement between solute and solvent in RPLC was proved to be universal in frontal analysis (FA). Based on the measured Z value in usual RPLC to be a constant and the quantitative determination of methanol increment in mobile phase in FA, the stoichiometric displacement (SD) between insulin and methanol was directly proved by the experiment. The SD was also proved to occur only on about the one fourth of the maximum amount of adsorbed methanol in the bonded phase layer (BPL) without any dynamic problem of mass transfer, while in FA, the SD firstly occurs on the surface of the BPL and then gradually sinks into the deeper sites companied with a dynamic problem. Although the displaced solvent by the same solute is less in the former case, the SD is independent of how deep of the solute enters the BPL. In addition, the adsorbed amount of solute on an adsorbent not only depends on the numbers of the adsorbed layer on the adsorbent surface, but also on the extent of the complete removal of the displaceable solvent in the BPL. The physical fundamental of the SD and the methodology for investigation were also discussed.
