Download or read book The Synthesis and Characterization of Bonded Zwitterionic Stationary Phases for High Performance Liquid Chromatography written by Louis W. Yu and published by . This book was released on 1987 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Synthesis and Characterization of Bonded Stationary Phases in High Performance Liquid Chromatography written by Steven Douglas Fazio and published by . This book was released on 1985 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 The Synthesis and Characterization of Homopolypeptide Bonded Stationary Phases for Liquid Chromatography written by Barbara Ann Siles and published by . This book was released on 1993 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Liquid Crystal like Stationary Phases for High Performance Liquid Chromatography written by Zhuxu Wang and published by . This book was released on 1995 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Synthesis and Characterization of New Bonded Stationary Phases for HPLC written by Deepika Janga and published by . This book was released on 2004 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of C8 Bonded Stationary Phases for HPLC written by Xiaofang Pan and published by . This book was released on 2002 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Synthesis and Characterization of Reversed Phase Stationery Phases for High Performance Liquid Chromatography written by Karen Wink Barnes and published by . This book was released on with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Stationary Phases for Reversed phase Liquid Chromatography written by Dale Allen Shoemaker and published by . This book was released on 1992 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Characterization of Bonded Phases for High Performance Liquid Chromatography written by Klaus John Stetzenbach and published by . This book was released on 1980 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Preparation and Characterization of Well defined Chemically Bonded Stationary Phases for High Pressure Liquid Chromatography written by Gerrit Engbertus Berendsen and published by . This book was released on 1980 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 THE CHARACTERIZATION OF BONDED PHASES FOR HIGH PERFORMANCE LIQUID CHROMATOGRAPHY written by and published by . This book was released on 1980 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The physical and chemical nature of chemically bonded phases used in high performance liquid chromatography have been studied. These bonded phases were characterized by a variety of chromotographic and non-chromatographic experiments. The non-chromatographic techniques included 13C NMR and batch extraction methods. The role played by the bonded phase as well as the mobile phase in determining the retention characteristics of the "stationary phase" were determined. The retention of solute molecules on bonded phases was found to be a function of the chain length of the bonded phase, the chemical nature of the bonded molecule, and the type of organic modifier used in the mobile phase. The energetics of the solute-stationary phase interactions was determined by the differential enthalpy and was found to be indicative of a partitioning process between two liquid phases. The retention process was also affected by the surface coverage of the bonded molecule. Optimum retention and separation characteristics were obtained with a hydrocarbon bonded phase of high surface coverage when used with a mobile phase containing a very polar organic modifier. The efficiency of these bonded phases was found to be independent of chain length as well as surface coverage of the bonded molecule. Some bonded phases which have specific functionalities incorporated into the bonded molecule are not true reversed phases. The selectivity of the bonded phases towards polar solute molecules was found to be affected by the type of organic modifier used in the mobile phase. The major accomplishment of this work shows that the stationary phase consists of the bonded molecule as well as trapped mobile phase. The composition of this ternary mixture is a function of the type and amount of bonded material and the type and amount of organic modifier used in the mobile phase

Download or read book Preparation and characterization of well defined chemically bonded stationary phase for high pressure liquid chromatography written by Gerrit Engbertus Berendsen and published by . This book was released on 1980 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development and Characterization of New Stationary Phases for Hydrophilic Interaction Liquid Chromatography written by Mohammed Elsayed Abdelatif Ibrahim and published by . This book was released on 2014 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrophilic interaction liquid chromatography (HILIC) has gained high popularity among separation scientists in the last two decades due to its ability to retain polar analytes. Many new HILIC stationary phases with different selectivities have appeared in the recent literature. Such developments require tools which can classify and compare the selectivity of these HILIC columns. In this thesis, straightforward and simple selectivity plots were constructed and used to classify HILIC stationary phases into bare silica, zwitterionic, neutral and amine-based phases. Silica monoliths show weak retention under HILIC conditions. In this thesis, the HILIC retention characteristics of silica monoliths were enhanced through surface modification with hydrophilic cationic latex nanoparticles. High efficiency (H ~ 25-110 μm) separations of carboxylic acids, amino acids and nucleotides were achieved. Due to their positive charge, the latex nanoparticles introduce anion exchange as another source of interaction. Consequently, these latex coated silica monoliths should exhibit mixed mode (HILIC/anion exchange) retention. Herein, the mixed mode retention of three different latex coated silica monoliths was studied. The AS9-SC latex coated silica monolith possessing the highest ion exchange capacity (44.1 μeq/column) separated six chaotropic and kosmotropic anions in less than 2.5 min. Silica is chemically unstable under extreme pH conditions. On the other hand, porous graphitic carbon (PGC) has high pH stability. Being a hydrophobic material, typically usage of PGC is restricted to reversed phase chromatography. In the presented thesis, a carbon-based HILIC stationary phase was developed as a new class of HILIC stationary phases via diazonium chemistry. The potential of this phase (carboxylate-PGC) as a HILIC phase was demonstrated by separation of carboxylic acids, phenols, amino acids and nucleotides. Carboxylate-PGC phase showed different selectivity than 35 columns. The efficiency of carbon-based phases is lower than silica due to slow mass transfer kinetics. Herein, we developed a hybrid phase comprising of 5 μm core-shell silica particles coated with 50 nm anionic carbon nanoparticles. This hybrid phase exhibited the unique selectivity of carbon and the high efficiency of core-shell silica particles. Fast and high efficiency HILIC separations of carboxylates and pharmaceuticals were achieved with efficiencies up to 85,000 plates/m.

Download or read book Synthesis and Characterization of Silica Hydride based Pentynoic Acid Stationary Phase written by Nasrin Syed and published by . This book was released on 2016 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: High performance liquid chromatography is an important analytical technique used for the separation and identification of components in a mixture. The aim of this research project was to synthesize and characterize a silica hydride-based pentynoic acid stationary phase. Analytical techniques like elemental analysis and diffuse reflectance infrared fourier transform spectroscopy (DRIFT) were used to confirm the success of bonding between silica hydride and pentynoic acid moiety. The pentynoic acid Si-H column allows for retention of both polar and non-polar compounds by carefully selecting the concentration ratio of organic solvent to water in the mobile phase. The characterization of the column was done using a series of polar and nonpolar compounds by studying their aqueous normal-phase and reversed-phase chromatographic behavior. The interactions between the stationary phase and the analyte include both hydrophobic and ionic/electrostatic interactions. The effect of varying the pH of the mobile phase on retention time was examined. The column's ability to run under reverse and aqueous normal phase conditions provides unmatched versatility compared to type-B silica columns.