Investigation of Dynamically Coated Alumina Stationary Phases for Reversed Phase High Performance Liquid Chromatography PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Investigation of Dynamically Coated Alumina Stationary Phases for Reversed Phase High Performance Liquid Chromatography PDF full book. Access full book title Investigation of Dynamically Coated Alumina Stationary Phases for Reversed Phase High Performance Liquid Chromatography by Veronica Ferguson. Download full books in PDF and EPUB format.
Author: Veronica Ferguson
Publisher:
ISBN:
Category : High performance liquid chromatography
Languages : en
Pages : 120
Get Book Here
Book Description
Author: Veronica Ferguson
Publisher:
ISBN:
Category : High performance liquid chromatography
Languages : en
Pages : 120
Get Book Here
Book Description
Author: Tina M. Mannschreck
Publisher:
ISBN:
Category : Chromatographic analysis
Languages : en
Pages : 136
Get Book Here
Book Description
Author: Anil R. Raghani
Publisher:
ISBN:
Category : Proteins
Languages : en
Pages : 166
Get Book Here
Book Description
Author: Abdul-Wahab El-Rjoob
Publisher:
ISBN:
Category : Chemistry, Analytic
Languages : en
Pages : 256
Get Book Here
Book Description
In this research, sulfoxides and sulfones were used as mobile phase additives and the effects of these additives on the retention behavior of some non-polar, polar, and chelate analytes were studied. The results of these experiments showed that dibutyl sulfoxide has a large effect on the reduction of the retention volumes of caffeine and Cr(acac)$\sb3.$ The effect of dibutyl sulfone on the retention behavior of analytes was similar to the effect of dibutyl sulfoxide. Additives such as dibutyl sulfoxide can be used to reduce the amounts of organic modifiers needed in some HPLC separations and to reduce problem of solvent storage and disposal. Loading capacity studies of dibutyl sulfoxide on the C18 stationary phase proved that dibutyl sulfoxide is dynamically modify the C18 stationary phase in HPLC. Also, these studies showed that there was a simple linear relationship between the amounts of mmoles of dibutyl sulfoxide actually taken up by the stationary phase and the logarithm of the corrected retention volumes for caffeine, theophylline, and the Cr(acac)$\sb3$ chelate.
Author: Monika Johansson
Publisher:
ISBN:
Category : Ion exchange chromatography
Languages : en
Pages : 30
Get Book Here
Book Description
Author: Omar Abubaker Rbeida
Publisher:
ISBN:
Category :
Languages : en
Pages : 123
Get Book Here
Book Description
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 ....
Author: Brian Charles Trammell
Publisher:
ISBN:
Category :
Languages : en
Pages : 370
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 726
Get Book Here
Book Description
Investigation and control of alkylsilane stationary phase structure in reversed phase liquid chromatography is presented. Raman spectroscopy is used to probe thealkyl chain conformational order and interchain coupling as a function of various chromatographic conditions. A new method is further developed to fabricate alkylsilane stationary phases with controlled surface coverage. The alkyl chain conformational order and interchain coupling of a series of high-density docosylsilane (C22) bonded stationary phases is shown as a function of temperature, surface coverage, polymerization method, common solvents and solutes. The conformational order of C22 stationary phases is compared to that of octadecylsilane (C18) stationary phases to understand the chain length effect on stationary phase structure. The conformational order information as indicated by Raman spectral order indicators for a C22 phase are correlated with the capacity factor and separation efficiency for each solute studied to gain insight into the retention mechanism. These studies help to understand the origin of stationary phase shape selectivity and the separation process in general. Based on these results, the molecular pictures at the stationary phase/solvent interface are proposed. The effect of pressurized solvent environments on two C18 phases is studied to obtain direct evidence for changes in stationary phase structure due to pressure. These changes are compared to effects of solvation relative to air in the same solvents. In addition, Raman spectral order indicators are identified for perdeuterated alkyl-containing system. This study provides a foundation for studying stationary phase structure in complex systems comprised of long alkyl-containing solutes. A further development of a new method is presented as well for synthesizing alkylsilane stationary phases with precisely controlled surface coverage by using a displaceable surface template monolayer of n-alcohol. A mechanism for this process is proposed based on the studies of n-alcohol concentration and chain length effect on the stationary phase surface coverage. The utility of these new stationary phases as chromatographic support is demonstrated. The shape selectivity for these new phases is comparable to or better than similar phases prepared by conventional methods.
Author: Asanka Wijekoon
Publisher:
ISBN:
Category : High performance liquid chromatography
Languages : en
Pages : 274
Get Book Here
Book Description
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.
Author: Michael David Bair
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages :
Get Book Here
Book Description
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 (
