Experimental Analysis and Reconstruction of the Morphology of Particulate and Monolithic Chromatographic Beds

This dissertation is concerned with the acquisition of three-dimensional image data of chromatography columns in capillary format using confocal laser scanning microscopy as well as with the reconstruction and analysis of the acquired image data in view of the dispersive properties of the separation column. Key aspect in the characterization are radial heterogeneities because in UHPLC these heterogeneities contribute in large part to dispersive band broadening. Therefore, radial heterogeneities carry a particular significance in the development of chromatography columns of improved separation efficiency. Consecutively, the topics that are covered in the individual chapters of this work are being summarized: - Chapter 1 and 2 deal with the development of a sample setup for the aberration free optical imaging of capillary chromatography columns via confocal laser scanning microscopy. Additionally, image processing methods are presented that enable image restoration, particle detection, and segmentation of acquired image data. The image data were analyzed using chord length distributions and radial porosity profiles. Subsequent chapters are concerned with the application of the presented method. Herein, focus lies on a characterization of local structural density on the length scales used in J.C. Giddings’ eddy dispersion theory. - In Chapter 3 the separation efficiencies of eleven MTMS-hybrid monoliths were correlated with pore size distribution and wall attachment which outlines a fundamental problem that accompanies the preparation of capillary monoliths. - A first study on the influence of packing parameters on separation efficiency and bed morphology of packed beds was performed in Chapter 4. Six capillary columns of varying inner diameter from 10 µm to 75 µm were packed with 1.7 µm Acquity BEH particles and evaluated for their chromatographic and morphological properties. It was observed that separation efficiency would drop with increasing capillary i.d.. This could be explained by a lower packing density in the wall region of these capillaries. Furthermore, size segregation of particles was observed. - Chapter 5 discusses morphological differences between capillaries packed with core–shell particles and capillaries packed with fully porous particles. Owed to their differing production process the former do have a particle size distribution that is much narrower than the particle size distribution of fully porous particles, which yields a substantially different ordering of the particles in the wall region of the capillaries. - Chapter 6 compares a silica monolith and a sub-2 µm packing in 20 µm i.d. capillaries. The study discusses the microstructure of these columns with regard to transchannel, short-range interchannel, and transcolumn dispersion using the already established descriptors and discusses the potential of each kind of bed structure. - Chapter 7 picks up the results of Chapter 4 and shows how bed microstructure is affected by the slurry concentration used in the slurry packing process. The study showed that the previously observed size segregation of particles can be suppressed by increasing the slurry concentration yielding improved separation efficiency. The trade-off with higher slurry concentrations was an increased number of packing gaps, both in fully porous and core–shell packed beds. Once again, the chapter highlights the potential of using microscopic reconstruction and an analysis of macroscopic separation efficiency comprehensively and illustrates that the packing of beds of increasing inner diameter requires higher slurry concentrations. The concentrations should be chosen to suppress particle size segregation while keeping the amount of packing gaps as small as possible

Bibliography of Lewis Research Center technical publications announced in 1989

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1989. All the publications were announced in the 1989 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Microgravity Science and Applications: Program Tasks and Bibliography for Fiscal Year 1996

NASA's Microgravity Science and Applications Division (MSAD) sponsors a program that expands the use of space as a laboratory for the study of important physical, chemical, and biochemical processes. The primary objective of the program is to broaden the value and capabilities of human presence in space by exploiting the unique characteristics of the space environment for research. However, since flight opportunities are rare and flight research development is expensive, a vigorous ground-based research program, from which only the best experiments evolve, is critical to the continuing strength of the program. The microgravity environment affords unique characteristics that allow the investigation of phenomena and processes that are difficult or impossible to study an Earth. The ability to control gravitational effects such as buoyancy driven convection, sedimentation, and hydrostatic pressures make it possible to isolate phenomena and make measurements that have significantly greater accuracy than can be achieved in normal gravity. Space flight gives scientists the opportunity to study the fundamental states of physical matter-solids, liquids and gasses-and the forces that affect those states. Because the orbital environment allows the treatment of gravity as a variable, research in microgravity leads to a greater fundamental understanding of the influence of gravity on the world around us. With appropriate emphasis, the results of space experiments lead to both knowledge and technological advances that have direct applications on Earth. Microgravity research also provides the practical knowledge essential to the development of future space systems. The Office of Life and Microgravity Sciences and Applications (OLMSA) is responsible for planning and executing research stimulated by the Agency's broad scientific goals. OLMSA's Microgravity Science and Applications Division (MSAD) is responsible for guiding and focusing a comprehensive program, and currently manages its research and development tasks through five major scientific areas: biotechnology, combustion science, fluid physics, fundamental physics, and materials science. FY 1996 was an important year for MSAD. NASA continued to build a solid research community for the coming space station era. During FY 1996, the NASA Microgravity Research Program continued investigations selected from the 1994 combustion science, fluid physics, and materials science NRAS. MSAD also released a NASA Research Announcement in microgravity biotechnology, with more than 130 proposals received in response. Selection of research for funding is expected in early 1997. The principal investigators chosen from these NRAs will form the core of the MSAD research program at the beginning of the space station era. The third United States Microgravity Payload (USMP-3) and the Life and Microgravity Spacelab (LMS) missions yielded a wealth of microgravity data in FY 1996. The USMP-3 mission included a fluids facility and three solidification furnaces, each designed to examine a different type of crystal growth