Digitized by Kansas Correctional Industries

Typescript. / Digitized by Kansas Correctional Industries

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)

Optimization of preparative nonlinear chromatography was carried out for the first time for a biomolecule mixture. Conventional wisdom on optimization, which roots from analytical chromatography, dictates optimizing resolution in an analytical column and obtaining similar separation in a large column for isolation. Such a method of optimization significantly under uses the capacity of the column and consumes large quantities of mobile phase. Hence, in preparative chromatography, the objective function is productivity, a measure of compromise between the amount of feed that can be loaded on to the column and time. Here, we report results from optimization studies carried out on a closely related binary peptide mixture on an analytical reversed-phase column. The goal is to optimize productivity under various chromatographic modes nonlinear isocratic elution, gradient elution, stepwise elution and displacement chromatography. In each mode, feed mixtures at highest possible concentration (limited by solubility), for increasing feed volumes was used. Productivity was monitored for increasing feed volumes, and loading was stopped as it went through a maximum. However, in some cases, solubility limitations from one of the feed components prevented further increase in loading. Even with this constraint, high productivities (5-10 g product/L stationary phase-h) were achieved. Separate experiments were carried out to measure the adsorption isotherms of these peptides over the range permitted by solubility. Separations under nonlinear chromatographic conditions were applied to isolate commercially significant two microcystins (microcystin LR and microcystin LA) from a cyanobacterial process waste. Milligram-level loading of microcystins was obtained on a solid-phase extraction cartridge packed with 0.5 g of C������ stationary phase. The separations were first carried out on an analytical column and then scaled-up to a preparative column. We also report simple and economical process to purify phycocyanins and allophycocyanins from a cyanobactenal process waste stream for two kinds of applications food colorant and biomedical marker. A detailed design for the large-scale production of biliproteins for both applications is also presented. Economic evaluation of the process resulted in comparable costs with the current market price for food-grade product and substantially lower cost for the biomedical grade product. / Graduation date: 2001

Gradient elution chromatography is frequently used for the preparative separation of peptides and proteins. Separations at high loadings are often avoided because peaks become asymmetrical and saturate the detector. However, non-linear interactions which become important at high loadings may actually improve the separation with greater concentrations of the product being extracted. In this study, the separation of a mixture of two chemotactic peptides N-formyl-met-phe (X~phe) and N-formyl-met-trp (X~trp) was considered using reversed-phase (RP) chromatography. These runs were limited by the solubility of the peptides. The effects of solubility and feed conditions on the chromatograms were examined. Because of the poor solubility of the peptides in low organic solvent concentration, runs where feed conditions are different from the column inlet conditions were examined. Since these two components exhibit low selectivity on the RP column, separation is difficult. Productivities were obtained and compared for the preparative purification of these compounds using isocratic, stepwise and gradient elution with acetonitrile/buffer and methanol/water mobile phase conditions. Selectivity reversal was present in methanol/water conditions. Selectivity reversal implies that the order of retention of the feed compound changes as the mobile phase composition varies. Curved gradient shapes were used in an attempt to improve the separation under selectivity reversal limitation. Using a combination of solubility methods and non-linear interactions at high loadings, simultaneous concentration and purification was achieved. / Graduation date: 1998

Thesis (Ph. D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references (leaves 240-242).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: zirconia; protein purification; anion exchange; chicken egg white; expanded bed chromatography. Includes bibliographical references (p. 83-86).

No description available.

D. Tech. Chemistry / The avocado oil contains compounds with potency against ailments caused by some bacteria, fungi, viruses as well as some insects and parasites. Present in the oil are long aliphatic hydrocarbons (acetogenins) documented to have a wide range of biological activities such as anticancer, antibacterial, antifungal, insecticidal and nematocidal properties and as a result the oil is fast gaining popularity amongst consumers. The demand and popularity of the oil makes it a target for contamination and adulteration of with cheaper oils. Chromatographic techniques such as Gas chromatography (GC) and High performance liquid chromatography (HPLC) are the frequently used methods of oil analysis to safe guard against adulteration. Derivatization of acetogenins uniquely found in avocado oil would provide derivatives which can be used as markers for authentication of the oil, an alternative method to fatty acid methyl ester analysis.

No description available.