Thesis (Ph. D.)--University of Wisconsin--Madison, 1930. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 100-104.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1961. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 43).

Until recently, evaluation of the effectiveness of preservatives in emulsified systems has depended largely on time-consuming microbiological techniques. Mathematical models have now been developed which enable the amount of preservative necessary for adequate preservation to be calculated. Determination of the physico-chemical parameters for these models is again a time-consuming process, especially where complex emulsions are involved. In the present work a three-chambered dialysis method has been investigated. Using this method it is possible to determine the concentration of preservative in the various phases of an emulsion and thus the total concentration required for adequate preservation. Various factors affecting the distribution of preservatives between oil and water and the interaction between preservatives and surfactant are discussed. These factors are then related to the problem of the distribution of a preservative in an oil in water emulsion system. Methodology used to evaluate the various physico-chemical parameters is reviewed and equations for representing the results are discussed. The distribution of benzoic acid between peanut oil and water and mineral oil and water systems was studied over a wide concentration range. The interaction of benzoic acid with aqueous solutions of the nonionic surfactant cetomacrogol was studied using solubility and equilibrium dialysis techniques. The interaction of various other preservatives with aqueous solutions of the nonionic surfactant cetomacrogol was examined. A comparison was made of various methods of expressing this interaction. It is suggested that the Scatchard equation is the most satisfactory equation for describing the binding data. Binding parameters determined from a Scatchard plot in the concentration range of free preservative appropriate for antimicrobial activity were used to calculate the total concentration of preservative required in the surfactant solution. A three-chambered dialysis cell was used to estimate the distribution of benzoic acid between the oil phase and the aqueous phase of oil in water emulsions containing peanut oil or mineral oil. The method also differentiates between preservative bound, or solubilized, by the surfactant and free in the aqueous phase. The distribution data was plotted on a three-dimensional graph from which the total concentration of preservative needed to provide a given free concentration in the aqueous phase can be determined. Results from the dialysis method agree closely with those calculated using mathematical models for preservative distribution. Hence the three-chambered dialysis method provides a relatively simple direct method of determining the required preservative concentration without recourse to mathematical models. / Pharmaceutical Sciences, Faculty of / Graduate

No description available.

Typescript, etc. / Digitized by Kansas State University Libraries

Thesis (MSc (Biochemistry))--University of Limpopo, 2011. / The purpose of this study was to investigate the effects of bovine serum albumin (BSA), lipase and glutaraldehyde on the surface of polydimethylsiloxane (PDMS). PDMS blocks of 15 by 15mm were fabricated using replica micromolding. To determine the effects of BSA, clean PDMS blocks were immersed in 20, 50 and 100mg/ml BSA, respectively. For the effect of lipase, the concentration was 20, 50 and 70mg/ml. To determine the effect of glutaraldehyde, 5, 10, 20, 30, 40 and 50% concentration was used. All the PDMS blocks were immersed for 10, 20 and 30 minutes. The water contact angle was measured on all the PDMS surfaces, including a clean surface as a control. This analysis was done using a drop shape analyzer, DSA 100 machine. The PDMS surfaces were further analyzed by Fourier Transform InfraRed (FTIR spectroscopy), using a Pelkin-Elmer FT-IR spectrometer. PDMS blocks which were pre-immersed in 5% glutaraldehyde and then in BSA and lipase solutions, respectively, were also added for FTIR analysis. The water surface tension was measured for both BSA and lipase and interfacial tension was measured for glutaraldehyde, using the DSA 100. The results indicated that the water contact angle decreases after the PDMS surface has been immersed in all the solutions prepared. FTIR analysis showed new peaks on the PDMS surface immersed in BSA, and in BSA and glutaraldehyde; however, there were no peaks formed on the PDMS surface immersed in lipase and washed, in glutaraldehyde, and in lipase and glutaraldehyde together. Surface tension measurements showed that BSA and lipase decreases the surface tension of water. Interfacial tension measurements also showed that glutaraldehyde decreases the interfacial tension of oil. BSA, lipase and glutaraldehyde therefore decrease the hydrophobicity of the PDMS surface. BSA adsorbs on the PDMS surface and the adsorption is irreversible. The adsorption of lipase on the PDMS surface is reversible. Glutaraldehyde does not adsorb on the surface or the adsorption is not detectable. BSA, lipase and glutaraldehyde all have surface active properties. The CMC value of BSA is 50mg/ml and of lipase is 15mg/ml.

The fabrication, motion and behavior of small droplets are subjects under considerable current study. The possible applications include using droplets as actuators to enhance mixing, as chemical reactors and the formation of emulsions. Microfluidics provides a convenient means of producing droplets at the micro scale. The study is currently dominated by spherical systems where droplets are consistently spherical in nature. Various methods and geometries have been tested for fabricating these droplets but little research has been conducted towards producing non-circular droplets. While the fabrication of non-spherical droplets has been reported before control over their shape remains difficult to achieve. In this thesis, we present a method to fabricate droplets using shear focusing in an oil medium alternatively from two channels facing each other. The droplets produced are non-circular in shape, and their shape dynamically alters as they travel in the microfluidic channel. The size of the droplets can be controlled by the ratio of oil and water flow rates. Microscopic images have been presented that show the non-spherical shape of the droplets at the point of fabrication. Images taken at two points further along the microfluidic channel show how the shapes of these droplets change as they travel in the channel. There were three regimes of droplet shapes, circular, triangular and rectangular shapes that were determined by the packing ratio of water droplet in oil phase in microfluidic channels. All droplets formed in this experiment were monodispersed.

No description available.