Transport phenomena in continuous stationary phases
Abstract
The transport properties of a new chromatographic support recently developed in this laboratory were experimentally evaluated and correlated with a modified van Deemter equation. Experimental techniques for reproducibly packing columns with cylindrical rolls of woven cellulosic fabrics, also called rolled stationary phases, were a key step in investigating the properties of this material. Over 40 columns were packed and found to consistently give stable operating pressure for interstitial flow velocities up to 100 cm/min and plate heights of 2 to 20 mm. Retention behavior of molecular probes ranging in molecular weights from 18 to 2 million showed a sharp molecular cut-off at molecular weights equal to or greater than 3350. Improved plate heights were also obtained by detergent scouring and mild enzyme based surface cleaning methods, which decreased plate height by 50% or more. These results suggest that opening the yarn up may reduce flow impedances in a manner which reduces dispersion. Most importantly, the solute dispersion was found to be independent of flow rate for interstitial velocities greater than 20 cm/min. This is consistent with earlier observations of a flat plate height curve for other types of rolled stationary phases, and gives an indication that mobile phase flow occurs in the spaces between the fibers as well as the yarns of the textile fabric. An analysis of the theory of hydrodynamic chromatography in packed beds on non-porous spherical particles showed that this behavior is expected when convective flow dominates the solute transport process in the void volume between the nonporous particles. This concept was extended to the rolled stationary phases where fibers are the smallest structures in a macroporous assembly of yarns. Convective transport was shown to dominate over diffusive transport for probes whose molecular weight exceeded 3350. The rapid separation of protein, bovine serum albumin (MW = 66,000) from a small solute, NaCl, in 90 seconds or less indicated the potential usefulness of this type of stationary phase for rapid size exclusion chromatography. The utility of the approach was further illustrated by the rapid separation and partial removal of denaturants from a recombinant protein, secretory leukocyte protease inhibitor, which improved its processing into the renatured form.
Degree
Ph.D.
Advisors
Ladisch, Purdue University.
Subject Area
Agricultural engineering|Chemical engineering
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