| Two main objectives were achieved as a result of the work presented in this dissertation: (1) Expand the base of applicability of flow field-flow fractionation (flow FFF) and (2) Conduct theoretical and experimental studies to examine the completeness of the standard FFF model. Since flow FFF can, in principle, be used with any carrier liquid and because it is applicable to a broad range of macromolecular or particulate material, a flow FFF channel was fabricated that was capable of separating with aqueous or nonaqueous carriers.; In developing this system, perturbations that may alter standard FFF retention were carefully examined. In particular, correlation of silica particle retention and ionic strength demonstrated the necessity of special electrolyte conditions to minimize the effect of particle-wall interactions in tetrahyrdrofuran (THF). Various samples, particulate and macromolecular, and different types of carriers, aqueous and nonaqueous, were used to determine the separative capability of this flow FFF channel. Results indicate that this unique flow FFF channel has the ability of being utilized for a wide variety of different types of samples.; Furthermore, a temperature-controlled flow FFF system was developed that was capable of separating and characterizing particles and polymers dispersed in various media at elevated operating temperatures. This development enabled flow FFF to study samples which require increased temperatures to dissolve and to examine the effect of using temperature as a parameter in optimizing separation performance. In addition, this study analyzed the fundamental importance of precisely controlling channel operating temperatures. The influence of ambient temperature fluctuations was theoretically predicted using the standard FFF equation.; The effect of using asymmetrical electroosmotic flow was theoretically examined and compared to normal parabolic flow. It was shown that the electroosmotic velocity profile is more controllable than parabolic flow. In addition, it was revealed that electroosmotic flow has the ability to maintain a relatively high selectivity into the low diameter range and thus extend the lower limit of separable species where field-induced forces are small. Experimentally, a sed FFF system was constructed that was capable of utilizing electroosmotic flow. The differential separation of a latex bead mixture indicated the viability of using this type of flow. |
