The chromatographic behaviour of a new column packing for high performance size exclusion chromatography based on crosslinked polyacrylamide particles was studied. Experimental retention data for poly(ethylene glycol)and poly(ethylene oxide) standards in water and water-methanol mixtures showed that the separation mechanism is size exclusion, since a universal calibration plot based on hydrodynamic volume was obtained. For polysaccharide standards in water and water-methanol (80/20), the universal calibration was valid for molecular weights above 4 * 10~. Below this value, secondary mechanisms appear to be taking part in the separation since water-methanol (80/20) is a poor solvent for polysaccharides. Crosslinked polyacrylamide packings showed an interactive behaviour with tetrahydrofuran and dimethylformamide as eluents with polystyrene and poly( ethylene glycol )/poly(ethylene oxide) standards and the universal calibration was not valid.

M.Sc. (Chemistry) / Please refer to full text to view abstract

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The recent discovery of a number of metabolites of estrogens has necessitated the development of new methods for their analysis. The available methods of proven merit fall short of determining these newer fractions. Moreover, these methods are too time consuming to determine the daily excretion of estrogenic steroids. The development of a relatively rapid and highly sensitive methodfor the estimation of several estrogens was, therefore, undertaken. The procedure involves hydrolysis, extraction, preliminary purification and separation, acetylation and gas chromatography of the steroids. Simultaneous separation and quantification by gas-liquid chromatography (GLC) not only allows a more rapid analysis but sensitivity is also increased by the use of ionization detectors. Determination of the optimal flow rate of hydrogen, air and carrier gas was found necessary for obtaining maximum detection response. Detector linearity for seven estrogens over an adequate range was established. Since free estrogens suffer severe adsorption on the gas chromatographic column and generally do not separate well, the steroids were analyzed as suitable derivatives. After examining several such derivatives (acetates, formate, trifluoroacetate, trimethylsilyl ethers) the acetates were found to be most suitable for the specific purpose. Optimal conditions for the acetylation of steroids in submicrogram quantities were established. The effect of the solid support, stationary phase, priming of the column with estrogens and solvent impurity in quantitative analysis by gas chromatography was also investigated. Preliminary separation of estrogens into separate groups was necessary because of poor resolution and long retention times resulting in poor detector response. Moreover, in a crude urine extract, the large number of contaminants obscuring the peaks of the lesser estrogen components, mandated preliminary purification. Thin-layer chromatography crtc) was found to be a versatile tool for this purpose. Among several solvent systems developed, three were found to be eminently suitable. TLC in System I (benzene:ethyl acetate 1:1) separates the estrogens into four fractions: (a) estrone and 2-methoxyestrone, (b) ring-D-alpha-ketols and estradiol, (c) 16-epiestriol, and (d) estriol. Further TLC of fraction (b) in System II (pet. ether:dichloromethane:ethanol 10:9:1) was found necessary to separate these estrogens from the neutral 17-ketosteroid. An alternate method of preliminary purification and separation for the measurement of the three classical estrogens in low titer urine, involving alumina chromatography, has been developed. Following these preliminary procedures GLC permitted rapid separation and highly sensitive quantification of the individual fractions [TRUNCATED] / 2031-01-01

by Cheung Yiu-ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1990. / Includes bibliographies. / ACKNOWLEDGMENT / ABSTRACT / Chapter CHAPTER 1 --- GENERAL INTRODUCTION --- p.1 / Chapter 1.1 --- REVIEW OF GAS-LIQUID CHROMATOGRAPHY --- p.1 / Chapter 1.2 --- APPLICATION OF GAS-LIQUID CHROMATOGRAPHY IN DRUG ANALYSIS --- p.8 / Chapter 1.3 --- AIMS OF THE PRESENT WORK --- p.9 / REFERENCES --- p.11 / Chapter CHAPTER 2 --- GAS-LIQUID CHROMATOGRAPHIC DETERMINATION OF ACTIVE INGREDIENTS IN COUGH-COLD SYRUP FORMULATIONS --- p.12 / Chapter 2.1 --- INTRODUCTION --- p.12 / Chapter 2.2 --- EXPERIMENTAL --- p.16 / Chapter 2.3 --- RESULTS AND DISCUSSION --- p.22 / Chapter 2.4 --- CONCLUSION --- p.73 / REFERENCES --- p.74 / Chapter CHAPTER 3 --- "GAS-LIQUID CHROMATOGRAPHIC DETERMINATION OF ATROPINE SULFATE/HYOSCYAMINE SULFATE, HOMATROPINE HYDROBROMIDE AND HYOSCINE HYDROBROMIDE IN PHARMACEUTICAL PREPARATIONS" --- p.75 / Chapter 3.1 --- INTRODUCTION --- p.75 / Chapter 3.2 --- EXPERIMENTAL --- p.79 / Chapter 3.3 --- RESULTS AND DISCUSSION --- p.85 / Chapter 3.4 --- CONCLUSION --- p.126 / REFERENCES --- p.127 / APPENDIX --- p.128 / Chapter A.1 --- INTRODUCTION --- p.128 / Chapter A.2 --- EXPERIMENTAL --- p.129 / Chapter A.3 --- RESULTS AND DISCUSSION --- p.132 / Chapter A.4 --- CONCLUSION --- p.147 / REFERENCE --- p.147 / LEGENDS FOR FIGURES / LEGENDS FOR TABLES

No description available.

Separations depend on the molecular interactions occurring on retentive surfaces. Much time and effort is paid in the design and manufacture of chromatographic surfaces that enhance separation capability. This thesis explores some of the design concepts currently available in the market place, and while doing so, investigates the mode of retention on a range of solute species. The information gained from the investigation of the retention and thermodynamic retention behaviour of stationary phases, along with molecular modelling carried out on their stationary phase ligand conformation assists in the design of stationary phase materials that enhance separations. Results from this study indicate that the aromatic functionality on the Synergi-polar-RP column may be diminished, due to the orientation of the phenyl ring on the stationary phase surface. / Doctor of Philosophy (PhD)

Graduation date: 2005

For a number of reasons, miniaturization of chromatographic columns has been a general trend over the past three decades. Methods designed to enhance selectivity and efficiency can offer improved separation power and speed, expanding on the advantages of miniaturized columns. This dissertation describes novel approaches in this direction, focusing on two areas: the development of affinity-type sorbents for capillary HPLC derived from molecular imprinted polymers (MIPs) and the study of perfusive electroosmosotic flow (EOF) and its effect on efficiency in capillary electrochromatography (CEC). MIPs are synthetic polymers capable of selectively binding a template molecule incorporated prior to polymerization. MIPs prepared using nortripyline, a tricyclic antidepressant drug, were employed to screen a simulated chemical library, consisting of a series of structural analogs and related compounds. A parameter was introduced to quantify the selective retention of the analytes. Library compounds containing the major structural features of the template (ring structure and pendant 2�� amine) exhibited the highest affinity for the MIP. The use of macroporous packings under conditions of electroosmotic perfusion can result in improved chromatographic efficiencies. In this work, the performance of CEC columns packed with particles having different nominal pore diameters was investigated. The results indicate that perfusive EOF can yield significant gains in efficiency and speed, especially when wide pore packings and dilute buffers are employed. A model was developed that estimates the extent of perfusive EOF expressed as an effective particle diameter, d[subscript p,eff] The results suggest that the observed efficiency gains are not entirely due to smaller d[subscript p,eff] values and could perhaps be due to a decreased A term in the wide pore packings. The electrical conductivity of CEC columns was used to assess intraparticle flow permeability under conditions of perfusion. Results for the narrow pore (100 ��) column were in agreement with theory for nonporous spheres, indicating intraparticle current was negligible, while the wide pore (1000 and 4000��) columns exceeded theoretical values by a factor of two. These results provide evidence of the existence of "through-pores" and that intraparticle flow permeability (and potential for improved efficiency with perfusion) is greatest with wide pore packings. / Graduation date: 2001

The distribution of hydrophobic ionogenic organic compounds (HIOC's) between aqueous and nonaqueous phases has been investigated. The HIOC's are aniline and methyl substituted anilines. The aqueous phases are methanol-water mixed solvents with varying pH and ionic strength. The nonaqueous phases are silica and alkyl derivatized silica with ethyl- (C-2), octyl- (C-8), and octadecyl- (C-18) silanes. A gas-liquid equilibration method has been developed to determine the Henry's law constants and the activity coefficients of methyl anilines in methanol-water mixed solvents. The logarithm of the Henry's law constants vary quadratically with the volume fraction of methanol. The chromatographic study has been performed to investigate the effect of three mobile phase factors, fraction of methanol, pH, and ionic strength, on the retention of methyl anilines on different stationary phases. The logarithm of mass distribution ratios, log k's, of methyl anilines vary linearly with the volume fraction of methanol. The ratios of H / k' of methyl anilines increase with increase in methanol in the mobile phase, indicating an increase in the activity coefficients in the stationary phases. This observation is found to be true for different methyl anilines in different stationary phases. A partition model is presented to describe the effect of pH and ionic strength on the retention of HIOC's in the mobile phase. The variation in log k' among neutral and ionic methyl anilines can be explained by linear free energy relationships. Equations are established to predict retention of neutral or ionized methyl anilines from their octanol-water partition coefficients at any methanol content in the mobile phase. Acid dissociation constants of methyl anilines determined from the dependence of log k' on pH are in close agrement with those determined by potentiometric titrations. The effect of ionic strength on the retention of both neutral and ionic species of methyl anilines is negligible. That is, the contribution from electrostatic energy and salting out effect are not significant. The chromatographic study is extended to study the retention of methyl anilines on silica as a function of pH and methanol at a constant ionic strength. The dependence of retention on pH is qualitatively interpreted from an ion exchange reaction between the dissociated silanol groups in the surface and the ionized methyl anilines. The effect of methanol on the retention of methyl anilines and of pyridine on silica is described by a quadratic relationship between the log k' and volume fraction of methanol. / Graduation date: 1990

Caryolanemagnolol and clovanemagnolol promote neuronal regeneration in various cell and animal based assays. The protein targets of these natural products are not currently known. Derivatives of caryolanemagnolol and clovanemagnolol were synthesized for the purpose of affinity chromatography. The derivatives are accessed rapidly through optimized procedures. / text