Download or read book High Performance Micellar Liquid Chromatography with Silica based Stationary Phase Having Surface bound Cationic Surfactant written by Ying Zhang and published by . This book was released on 1995 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Micellar Liquid Chromatography written by Alain Berthod and published by CRC Press. This book was released on 2000-03-30 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: Micellar Liquid Chromatography reviews the use of surfactant solutions at or above the critical micelle concentration as mobile phases in liquid chromatography. It employs a computer-assisted optimization methodology and integrates micellar liquid chromatography (MLC) with other chromatographic and electrophoretic techniques using surfactants. It also includes the MICHROM software package on CD-ROM to facilitate the application of equations and optimize efficiency of MLC systems.

Download or read book Investigating Reaction Schemes for Improving Silica Based Monomeric Bonded Stationary Phases for Reversed Phase Liquid Chromatography written by Michael David Bair and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Central to the advancement of reversed-phase high-performance liquid chromatography (RPLC) is to develop new synthetic strategies for manufacturing stationary phase materials. Methods to improve the efficiency, retention properties, and chemical stability of stationary phases are always being investigated. The work presented focuses on two new synthesis schemes aimed at improving monomeric silica-based stationary phases in these respects. The first study involves "pre-capping" Type-B silica. Previous work showed that monomeric stationary phases made by pre-treating the silica surface with small amounts of trimethylsilane (TMS) reagents prior to C18 silanization showed vast improvements in the chromatographic efficiency, phase loading, and retention with a maximum at approx. 5% pre-capping. It was concluded that this pre-capping step improved efficiency by selectively neutralizing the most reactive highly-acidic silanol sites, so-called silanol "hot spots," producing a more energetically-homogenous surface prior to exhaustive C18 derivatization that subsequently yielded a more evenly-distributed alkyl bonding arrangement. These previous studies were performed on Type-A silica, an older variety of silica gel material containing higher levels of metal impurities than the Type-B silica used today. It has since been argued that metallic impurities are the primary cause of silanol hot-spots, and that pre-capping Type-B silica would have little or no effect, however the experimental evidence has yet to be produced, and there exists the potential for heterogeneous silanol reactivity inherent in the amorphous silica gel regardless of purity. The purpose of the work presented here is to determine the effects of TMS pre-capping on Type-B silica as compared to the previous Type-A results, with the goal of establishing pre-capping protocol for Type-B silica and to form a better understanding of its chemistry. The current work performed on three Type-B silica substrates of various physical and chemical properties demonstrated optimal TMS pre-capping at approximately 2.5%. The results at this level show only a slight improvement in efficiency for non-polar compounds ( 25%) was observed for some drug compounds and bases under buffered conditions, with the magnitude of the improved efficiencies correlating with metal impurity content and physical parameters of the silica substrate. Pre-capping also resulted in a slight decrease in retention and hydrolytic stability due to a decrease in bonded phase density. The results lend supporting evidence that metal impurities are the primary source of highly acidic silanols, but they also suggest a means to improve efficiency of basic analytes on certain Type-B silica substrates. It was concluded that TMS pre-capping Type-B silica is best done at low levels (

Download or read book The Essence of Chromatography written by C. F. Poole and published by Elsevier. This book was released on 2003 with total page 940 pages. Available in PDF, EPUB and Kindle. Book excerpt: General concepts in column chromatography -- The column in gas chromatography -- Instrumental aspects of gas chromatography -- The column in liquid chromatography -- Instrumental aspects of liquid chromatography -- Thin-layer chromatography -- Supercritical fluid chromatography -- Capillary-electromigration separation techniques -- Spectroscopic detectors for identification and quantification -- Separation of stereoisomers -- Laboratory-scale preparative chromatography.

Download or read book Liquid Chromatography written by K.K. Unger and published by Elsevier Inc. Chapters. This book was released on 2013-01-08 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: This chapter deals with the most important part of the LC system: the column enabling the efficient and fast resolution of complex mixtures. It is divided into seven sections under the overall aspects of manufacture, operation, and evaluation of analytical columns for the user. The first three sections highlight the column design and hardware, followed by a thorough treatment of the properties of microparticulate silica adsorbents as packing material, stationary phases performed by surface functionalization, and the column filling process. Then, the implementation of the column into the LC system is discussed, leading into chromatographic column testing as a C18 bonded reversed silica column and its maintenance. Section 3.7 is devoted to today’s column market, focusing on the three main types of silica columns: fully porous microparticulate silica columns , columns with core–shell silica particles, and monolithic silica columns. Within a period of 40 years, analytical HPLC has generated high-resolution, robust, and rugged reversed-phase silica columns, which enable efficient, highly sensitive, and fast separations of low-molecular-weight substances based on validated methods.

Download or read book Evaluation of a Silica Hydride based Undecynoic Acid Stationary Phase for High Performance Liquid Chromatography written by Veena Menon Kozhikote and published by . This book was released on 2016 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Undecynoic acid (UDA) attached to a silica hydride surface has been found to exhibit weak cationic exchange properties and an aqueous normal phase (ANP) type of retention. ANP is a mechanism similar to normal phase chromatographic retention, except for the use of a polar solvent such as water in the mobile phase. In ANP, the retention of a polar molecule is increased with a higher concentration of the non-polar mobile phase solvent (usually acetonitrile). Non-polar molecules exhibit retention behavior as in reverse phase (RP) chromatography. The goal of this research was to characterize the chromatographic retention pattern of an undecynoic based silica hydride column by studying various polar and nonpolar analytes. Also investigated were the effects of varying the buffer concentrations -formic acid and ammonium acetate and the effect of temperature on the retention of selected compounds. It has been established from the current work that a silica hydride based UDA column can be used for separation and analysis of nucleotides and nucleosides as well as phenolic acid components in pomegranate peel samples. A phenyl hydride column was additionally used to complete the study on the peel samples since the UDA column was not effective in separating isobaric compounds found in the peels. In conclusion, silica hydride based UDA column has been found to exhibit dual retention capabilities for polar and non-polar molecules.

Download or read book The Synthesis and Characterization of Reversed Phase Stationary Phases for High Performance Liquid Chromatography written by Karen Wink Barnes and published by . This book was released on 1986 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reversed phase liquid chromatography (RPLC) is a widely used separation technique today. The stationary phase, composed of hydrocarbon moieties chemically bound to a silica support, is commonly prepared by refluxing the silica with a reactive silane in an appropriate solvent. Siloxane bonds, Si-O-Si, are formed. There are limitations to RPLC in that nonhomogeneous surface coverages, detrimental to efficient separations, result from the bonding process, and because the reaction is never complete due to steric restrictions. Also, silica is soluble at high pH values, and the Si-C bond binding the hydrocarbon to the silica is labile at low pH ranges. Thus, the usable pH range for silica stationary phases is 2.5 to 7.5, and often this range is too narrow to allow the separation of a mixture. The use of ultrasonic cavitation to catalyze silane bonding was investigated to dtermine whether the vigorous ultrasonic process would drive reagents into the surface pores and better distribute the hydrocar bonaceous reagent, thereby producing a more efficient stationary phase. Tandem reactions proved that ultrasonic bonding procedures are as effective as the refluxed, and that the chromatographic efficiency of the ultrasonic phases was comparable, if not superior, to the refluxed. Chromatographic tests also indicated the ultrasonic phases were comparable to commercially available phases. The reproducibility of the reactions and the effect of acoustic power and heat were also investigated. A second set of experiments investigated substitution of alumina for silica because the alumina crystalline structure remains intact over a pH range of 2 to 12. A trifunctional modification scheme generating a thick cross-linked hydrocarbon matte was used because the Al-0 bond is susceptible to hydrolysis, which strips the bound hydrocarbons, by polar RP solvents. Five aluminas were bonded and tested for chromatographic utility. Reaction conditions were optimized, and ultrasonic bonding was investigated. It was found that alumina with a sufficiently active surface is modifiable, and that the modified surface is remarkably stable for use with acidic and basic buffers and in neutral, polar solvent mixtures. The chromatographic utility of alumina phases was demonstrated and compared with the silica results.

Download or read book Micellar Chromatography Optimization and Use written by Pter Cege Nganga and published by . This book was released on 1985 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Efficiency Enhancements in Micellar Liquid Chromatography Through Selection of Stationary Phase and Mobile Phase Organic Modifier written by David Paul Thomas and published by . This book was released on 2009 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of a Silica Hydride Based Diol Stationary Phase for High Pressue Liquid Chromatogrphy written by Kathleen Talbott and published by . This book was released on 2016 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: The impact of chromatography across many scientific fields and applications is limitless. It is a vital everyday separation, characterization, and purification tool for many scientists worldwide. Innovations in high performance liquid chromatography (HPLC) stationary phases have led to more diverse separations essential to many fields including the pharmaceutical industry and research. Silica hydride based stationary phases have been shown to display both reverse phase (RP) and aqueous normal phase (ANP) chromatographic behavior. This is a result of both the silica hydride surface and the bonded phase. The goal of this work was to characterize silica hydride based diol stationary phases for HPLC. A wide range of compounds with varying polarities were analyzed. Retention was observed under ANP and RP conditions. Two representative silica hydride based diol stationary phases were compared to demonstrate the effect that the length of the bonded phase has on the separation capabilities of the column. The diol bonded phase with a longer carbon chain retained analytes with more hydrophobic (or non-polar) characteristics longer than analytes with more hydrophilic properties. As part of a larger study the effect of buffer concentration on the ANP retention of model compounds was investigated. Retention dramatically decreased when the concentration of some buffers was increased. This trend is opposite of what has been observed in hydrophilic interaction liquid chromatography (HILLIC), indicating a clear distinction in the retention mecahism for HILLIC and ANP.

Download or read book Preparation and Characterization of Multifunctional Stationary Phases for Multimode Separations written by Asanka Wijekoon and published by . This book was released on 2010 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: High performance liquid chromatography is a powerful analytical technique employed to separate analyte mixtures. Since biomedical sample mixtures contain a very diverse range of compounds; one chromatographic mode is usually unable to separate all components of the mixture. Therefore, there is an increasing need for faster and efficient separations with a broad range of selectivity. To attain better selectivity and efficient separation, and to improve the versatility of the chromatographic column, a new way of preparation of multifunctional stationary phases, suitable for use in multiple chromatographic separation modes, is described. The preparation of multifunctional stationary phases takes advantage of Schiff base chemistry in two different synthetic routes. The first route involves reductive coupling of amino bonded silica with aldehyde containing ligands. The coupling of aldehyde bonded silica with amine containing ligands is the other reaction route. Aldehyde terminated silica is a versatile reactive platform that enables the synthesis of a wide range of stationary phases by attaching amine containing ligands that have diverse functionality. Here the preparation of aldehyde terminated silica was achieved by bonding aldehyde silane to the silica surface. Preparation of aldehyde silane is a novel approach and a successful synthetic scheme of making acetalated aromatic aldehyde silane (AAS- Aldehyde group in the silane has been protected by acetalation) and aromatic aldehyde silane (AS) is invented. The studies confirmed that the synthesized multifunctional chromatographic stationary phases were capable of operating in ion exchange mode, reversed phase mode and hydrophilic interaction liquid chromatographic mode. The studies further concluded that those surfaces have good selectivity for the separation of small polar and charge molecules. The application of the well established Schiff base reaction allowed the incorporation 2H to the bonded phases and is utilized to study the motional dynamics of the bonded ligands in the surface at different temperatures in the presence of a broad range of solvent systems by using 2H wide line NMR spectroscopy. The investigation provides information about the motional dynamic heterogeneity of the bonded ligands, which reflects the existence of surface heterogeneity of the surface.

Download or read book High Performance Liquid Chromatography written by Mary T. Gilbert and published by Elsevier. This book was released on 2013-10-22 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: High Performance Liquid Chromatography focuses on the developments, operating techniques, practices, equipment, and packing materials involved in High Performance Liquid Chromatography (HPLC). The book first offers information on basic chromatographic theory, equipment, and the column. Topics include resolution, efficiency, pumps and gradient systems, connectors, detectors, injectors, column packing and testing, packing materials, and coupling of columns. The text also ponders on sample treatment and separation methods, as well as trace analysis, reversed phase chromatography, and selection/optimization conditions. The publication examines adjustment of selectivity by the use of eluent additives and preparative liquid chromatography. Discussions focus on chromatography on dynamically modified oxide gels, metal complexation, crown ethers, ion pair chromatography, materials for preparative chromatography, and separation strategy. The text also reviews the trends in the practice of HPLC and chiral chromatography. The book is a dependable reference for readers interested in High Performance Liquid Chromatography.

Download or read book Quantitative Structure written by Roman Kaliszan and published by Wiley-Interscience. This book was released on 1987-10-14 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of computers in numerical characterization of molecular structures has given chemists fundamentally new information on chemical structures, leading to major developments in physical, analytical, and medicinal chemistry. This book, written by a pioneer in the field, extends and updates research on quantitative structure retention relationships (QSRR) by consolidating and critically reviewing the extensive literature on the subject while providing basic theoretical and practical information required in all investigations involving chromatography, analytical chemistry, biochemistry, and pharmaceutical research. Coverage includes detailed discussions of the general theories and mechanisms of chromatographic separations, prediction of retention coefficients, statistical techniques and formal requirements of QSRR studies, specific applications of chromatographic data, and much more. Also provides several carefully selected figures and tables plus extensive bibliographies.

Download or read book Application of NOVEL Stationary Phases in High Performance Liquid Chromatography written by Omar Abubaker Rbeida and published by . This book was released on 1995 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: The reversed-phase-silica bonded packing materials have been the most regularly used phases for the analysis of drugs and related substances for 3 decades. During that time they have been used in assay procedures and stability indicating assay method in dosage forms and in the biological fluids. However, these phases have continued to display disadvantages which effect their efficient operation which includes the solubility of the silica matrix and the detachment of the bonded layer at high and low pH ranges respectively, the difficulty to reproduce the same bonded stationary phases, and the major detrimental contribution of the silanol groups on the silica surface have affected also retention behaviour and stability of the assay. Therefore in this work the introduction of alternative stationary phases to substituted silica is considered. Alumina-bonded C,18, a Buckyclutcher column and a carbon fiber column have all been examined for their stability under aggressive conditions, and their retention behaviour and their capability to retain and resolve compounds better than silica bonded phases was studied. By using alumina C,18 stationary phase it was possible to resolve the amino alcohol, atenolol from its widely chemically different related substances and assay it in a tablet dosage form with good precision ....

Download or read book Green Analytical Chemistry written by Miguel de la Guardia and published by Elsevier. This book was released on 2010-10-27 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides basic coverage of the fundamentals and principles of green chemistry as it applies to chemical analysis. The main goal of Green Analytical Chemistry is to avoid or reduce the undesirable environmental side effects of chemical analysis, while preserving the classic analytical parameters of accuracy, sensitivity, selectivity, and precision. The authors review the main strategies for greening analytical methods, concentrating on minimizing sample preparation and handling, reducing solvent and reagent consumption, reducing energy consumption, minimizing of waste, operator safety and the economic savings that this approach offers. Suggestions are made to educators and editors to standardize terminology in order to facilitate the identification of analytical studies on green alternatives in the literature because there is not a wide and generalized use of a common term that can group efforts to prevent waste, avoid the use of potentially toxic reagents or solvents and those involving the decontamination of wastes. provides environmentally-friendly alternatives to established analytical practice focuses on the cost-saving opportunities offered emphasis on laboratory personnel safety

Download or read book Synthesis and Characterization of Surface confined Ionic Liquid Stationary Phases for High Performance Liquid Chromatography written by David S. Van Meter (III.) and published by . This book was released on 2008 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Exploration in Analytical Separations Using High Performance Liquid Chromatography written by Yaqin Sun and published by . This book was released on 2006 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique solvation properties of ionic liquids (ILs) are being used to advantage in the dissolution of a wide range of organic and inorganic substances, including both neutral and charged species. Investigations of the physicochemical properties of ILs and solute/stationary-phase interactions in GC suggest that ILs may be useful as multimodal media in chromatographic separations. In this work, a butylimidazolium cation with a Br- counter-ion was immobilized on porous silica particles and examined as a stationary phase for LC. In chromatography, the LSER methodology has been used to correlate retention with fundamental solute/mobile-phase and solute/stationary-phase properties. The present study has established a relationship between the system constants and properties of an IL-type stationary phase by the LSER approach. It focuses on characterizing solute retention using methanol-water and acetonitrile-water binary mobile phases. Results are discussed in terms of the chemical meaning of the magnitude of the coefficient as well as its sign and the effect of mobile-phase composition. These results and further comparisons with conventional systems confirm the presence of the hydrophobic retention property and the importance of the ion-dipole/dipole-dipole retention mechanism for two stationary phases (the butylimidazolium-based and a commercial anion exchange). The impact of organic modifiers on separation of selected compounds is also discussed. In addition, the primary results of the LSER extension for modeling retentions of some ionizable compounds, as well as error propagations in retention, are presented. The preliminary application of IL-based stationary phase on polyphenol separation will be examined.