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Frontal Analysis (frontal + analysis)
Selected AbstractsDetermination of adsorption isotherms by means of HPLC: Adsorption mechanism elucidation and separation optimizationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 5-6 2009Nicola Marchetti Abstract The purpose of this review is to illustrate the most important techniques for isotherm determination by means of HPLC. Starting on the traditional Frontal Analysis approach, Frontal Analysis by Characteristic Point, Elution by Characteristic Point, Perturbation Method in its different applications will be considered to conclude with the most recent Inverse Method approach. Since many of these techniques are based on the fundamentals of nonlinear chromatography, a short overview of the theory of nonlinear chromatography is presented. Emphasis is given to the most recent applications of these techniques for pharmaceutical applications, characterization of binding mechanisms, bioaffinity studies, molecular and chiral recognition processes. [source] Prediction of Band Profiles of Mixtures of Bradykinin and Kallidin from Data Acquired by Competitive Frontal AnalysisBIOTECHNOLOGY PROGRESS, Issue 3 2003Dongmei Zhou The competitive adsorption isotherms of two closely related peptides, bradykinin and kallidin, were measured by frontal analysis on a Zorbax SB-C18 microbore column. An aqueous soluton at 20% acetonitrile (0.1% TFA) was used as the mobile phase. The competitive isotherm data were fitted to four different models: Langmuir, Bilangmuir, Langmuir-Freundlich, and Toth. These data fitted best to a Bilangmuir isotherm model. The influence of the pressure on the retention factors of the two peptides was found to be small and was not investigated in detail. The band profiles of large samples of the single components and of their mixtures were recorded. The overloaded profiles calculated using either the equilibrium-dispersive or POR model are in excellent agreement with the experimental profiles in all cases. Our results confirm that the competitive isotherm data derived from mixtures may suffice for a reasonably accurate prediction of the band profiles of all mixtures of the two components, provided their composition is close to 1/1. [source] Small molecule adsorption on to polyester capillary-channeled polymer fibers: Frontal analysis of naphthalene and naphthol (naphthalene and naphthol adsorption on capillary-channeled polymer fibers)JOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2010Christine M. Straut Abstract Frontal analysis was carried out employing poly(ethylene-terephthalate) capillary-channeled polymer fibers as the stationary phase for the immobilization of low-molecular-weight polycyclic aromatic hydrocarbon compounds (naphthol and naphthalene) from 2% methanol/water solutions. The effects of several experimental parameters on the frontal profile, the breakthrough volume, and the equilibrium parameters were determined for each solute. The amount adsorbed at exhaustion of naphthalene and naphthol was also compared. The kinetics and thermodynamics were maintained at relatively fast flow rates/linear velocities (,6,18,mm/s). Comparisons of dynamic capacity revealed that naphthalene was more retained than naphthol, in most situations more than five times that of the naphthol adsorption. This increase in capacity is most likely due to the multilayering of naphthalene on the surface of the fibers through ,,, interactions between the solute and the fiber surface and successive layering of solute molecules. The extent of layering is a function of the flow, with faster flow rates (and subsequent shear forces) reducing the extent of adsorbate,adsorbate interactions. Although the overall loading capacity of the capillary-channeled polymer fibers is far below porous phases, there are a number of attractive attributes that support further development. [source] Drug,liposome distribution phenomena studied by capillary electrophoresis-frontal analysisELECTROPHORESIS, Issue 16 2008Jesper Østergaard Professor Abstract The potential of using CE frontal analysis (CE-FA) for the study of low-molecular-weight drug,liposome interactions was assessed. The interaction of bupivacaine, brompheniramine, chlorpromazine, imipramine, and ropivacaine with net negatively charged 80/20,mol% 1-oleoyl-2-palmitoyl- sn -glycero-3-phosphocholine/egg yolk phosphatidic acid liposome suspensions in HEPES buffer at pH,7.4 was investigated. The fraction of free drug as a function of lipid concentration was measured and apparent liposome , buffer distribution coefficients were determined for the basic drug substances. The distribution coefficients increased in the order ropivacaine, bupivacaine, brompheniramine, imipramine, and chlorpromazine. The developed CE method was relatively fast allowing estimates of drug,liposome affinity to be obtained within 15,min. CE-FA may have the potential to become a valuable tool for the characterization of drug,liposome interactions in relation to estimation of drug lipophilicity and for the evaluation of drug distribution in liposomal drug delivery systems. [source] CE frontal analysis based on simultaneous UV and contactless conductivity detection: A general setup for studying noncovalent interactionsELECTROPHORESIS, Issue 3 2007Henrik Jensen Dr. Abstract CE frontal analysis (CE-FA) has been established as a powerful tool to study noncovalent interactions between macromolecules and small molecules such as drug substances or pharmaceutical excipients. However, when using traditional commercial CE instrumentation, a serious drawback is related to the fact that only UV-active compounds can be studied. In recent years, contactless conductivity detection has become an attractive alternative to UV detection in CE due to its high versatility. In this study, we combine contactless conductivity detection and UV detection in a highly versatile setup for profiling noncovalent interactions between low-molecular-weight molecules and macromolecules. In the case of molecules having a chromophore the setup allows determination of binding constants using two independent detectors. The new contactless conductivity detection cell is compatible with commercial CE instrumentation and is therefore easily implemented in any analysis laboratory with CE expertise. [source] Biporous polymeric beads fabricated by double emulsification for high-speed protein chromatographyJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Guo-Yong Sun Abstract Rigid biporous beads (BiPB) were fabricated by double emulsification. An aqueous suspension of superfine calcium carbonate granules and organic solvent were used as porogenic agents to create superpores and micropores, respectively. The polymerization of monomers, glycidyl methacrylate, and ethylene glycol dimethacrylate was initiated with benzoin ethyl ether by ultraviolet irradiation. Modified with diethylamine (DEA), the BiPB were derivatized into an anion-exchange medium (which is denoted as DEA,BiPB). The DEA,BiPB with an average diameter of 46.3 ,m was characterized to possess two types of pores, that is, micropores (20,200 nm) and superpores (500,5300 nm). Flow hydrodynamic experiments showed that the DEA,BiPB column had a smaller backpressure than that of the conventional microporous beads column at a given flow rate. The static adsorption capacity of the DEA,BiPB was close to that of the DEA,MiPB for bovine serum albumin. However, frontal analysis demonstrated that the dynamic binding capacity of the DEA,BiPB column was two times higher than that of the DEA,MiPB at a flow rate of 1800 cm/h. Moreover, the purification of the molecular chaperone GroEL was carried out with the DEA,BiPB column at two flow rates (150 and 1500 cm/h). This showed that the GroEL purification was nearly the same at the two flow rates tested. These results indicate that the DEA,BiPB column is promising for high-speed protein chromatography. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 17,23, 2007 [source] Separation of chiral mixtures in real SMB units: The FlexSMB-LSRE®AICHE JOURNAL, Issue 1 2010Pedro Sá Gomes Abstract In this work, a procedure for the separation of a racemic mixture of guaifenesin onto a chiral stationary phase (Chiralpak AD), by means of Simulated Moving Bed (SMB) technology, is presented in four major steps: (1) search for the suitable stationary and mobile phases; (2) determination of sorption parameters and validation by frontal analysis; (3) modeling and design of the SMB unit; and (4) operation and demonstration. A major emphasis is given to the common deviations that "real" SMB units present when compared with the theoretical apparatus (due to tubing and equipment dead volumes, switching time asymmetries and delays, pumps flow rates variations). These deviations are analyzed before and after the design and construction of the FlexSMB-LSRE® unit, a new flexible unit, hereby presented. A detailed model that takes into account tubing and equipment dead volumes, as well as switching time asymmetries and delay, was used to study and compare different dead volumes design and compensating strategies. It is shown that all these approaches can be converged into a switching time compensating strategy. This approach served to predict the experimental operating conditions and run a classical SMB experiment, which afterwards was compared with the simulated profiles obtained for the FlexSMB-LSRE® unit. The result of the separation was guaifenesin enantiomers with purities above 98% and a productivity value of 23 genantiomer/(dm3 CSP day). © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Single run measurements of drug-protein binding by high-performance frontal analysis capillary electrophoresis and mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2005Hong Wan A novel drug-protein binding measurement method based on high-performance frontal analysis and capillary electrophoresis (HPFA/CE) is presented. A single run measurement approach is proposed to circumvent utilization of a calibration curve that is often performed with HPFA. A sensitive mass spectrometer is applied as a detector enabling the measurement of in vitro protein binding at lower drug concentrations. Unbound free fraction and binding constants can be determined by a single run measurement by consecutive injections of an internal drug standard, a buffer plug and a drug-protein mixture. Effects of injection volumes on peak height and plateau profile were investigated in two different separation systems, non-volatile buffer and volatile buffer, with UV and mass spectrometry detection, respectively. A simplified one-to-one binding model is employed to evaluate the proposed method by using both single and multiple drug concentrations to measure the unbound free fraction and calculate the binding constants of some selected compounds. The method is suitable for rapid and direct screening of the binding of a drug to a specific protein or drug-plasma protein binding. Copyright © 2005 John Wiley & Sons, Ltd. [source] Study of nobiletin binding to bovine serum albumin by capillary electrophoresis,frontal analysis and circular dichroismBIOMEDICAL CHROMATOGRAPHY, Issue 9 2010Lian Yi Abstract A very recent epidemiological study provided strong support for nobiletin (NOB) as a potential candidate chemopreventive agent against cancer. From the pharmacology point of view, drug,protein interactions are determining factors in therapeutic, pharmacodynamic and toxicological drug properties. In this work, for the first time, detection of NOB at near-physiological conditions was accomplished by means of capillary electrophoresis,frontal analysis (CE-FA), and then the binding constants of NOB with bovine serum albumin (BSA) at the same conditions were determined. Complexation of NOB,BSA led to a decrease of the height for free NOB with increasing concentration of BSA. These results revealed the presence of a single class of binding site on BSA, and provided the binding constant of 103/m, showing the strong affinity of NOB for BSA. Furthermore, circular dichroism spectra showed that, when the molar ratio of NOB to BSA was up to 2:1, NOB did not affect the overall protein conformation significantly and the protein thus retained a native-like structure. These results may provide important information for preclinical studies of nobiletin in pharmaceutical research. Copyright © 2010 John Wiley & Sons, Ltd. [source] Prediction of Band Profiles of Mixtures of Bradykinin and Kallidin from Data Acquired by Competitive Frontal AnalysisBIOTECHNOLOGY PROGRESS, Issue 3 2003Dongmei Zhou The competitive adsorption isotherms of two closely related peptides, bradykinin and kallidin, were measured by frontal analysis on a Zorbax SB-C18 microbore column. An aqueous soluton at 20% acetonitrile (0.1% TFA) was used as the mobile phase. The competitive isotherm data were fitted to four different models: Langmuir, Bilangmuir, Langmuir-Freundlich, and Toth. These data fitted best to a Bilangmuir isotherm model. The influence of the pressure on the retention factors of the two peptides was found to be small and was not investigated in detail. The band profiles of large samples of the single components and of their mixtures were recorded. The overloaded profiles calculated using either the equilibrium-dispersive or POR model are in excellent agreement with the experimental profiles in all cases. Our results confirm that the competitive isotherm data derived from mixtures may suffice for a reasonably accurate prediction of the band profiles of all mixtures of the two components, provided their composition is close to 1/1. [source] Immobilized Metal Affinity Chromatography without Chelating Ligands: Purification of Soybean Trypsin Inhibitor on Zinc Alginate BeadsBIOTECHNOLOGY PROGRESS, Issue 1 2002Munishwar N. Gupta Immobilized metal affinity chromatography (IMAC) is a widely used technique for bioseparation of proteins in general and recombinant proteins with polyhistidine fusion tags in particular. An expensive and critical step in this process is coupling of a chelating ligand to the chromatographic matrix. This chelating ligand coordinates metal ions such as Cu2+, Zn2+, and Ni2+, which in turn bind proteins. The toxicity of chemicals required for coupling and their slow release during the separation process are of considerable concern. This is an important issue in the context of purification of proteins/enzymes which are used in food processing or pharmaceutical purposes. In this work, a simpler IMAC design is described which should lead to a paradigm shift in the application of IMAC in separation. It is shown that zinc alginate beads (formed by chelating alginate with Zn2+ directly) can be used for IMAC. As "proof of concept", soybean trypsin inhibitor was purified 18-fold from its crude extract with 90% recovery of biological activity. The dynamic binding capacity of the packed bed was 3919 U mL -1, as determined by frontal analysis. The media could be regenerated with 8 M urea and reused five times without any appreciable loss in its binding capacity. [source] | |||||||||||||