Recent Research Developments

October 18, 2000
 

Monodisperse and Nonporous Zirconia Microspheres Designed for Ultrafast Chromatography

Professor Peter W. Carr of the Chemistry Department, Professor Alon V. McCormick, and a postdoctoral research associate Bingwen Yan of the Department of Chemical Engineering and Material Science (CEMS), in collaboration with ZirChrom Separations, Inc. (Anoka, MN), have developed a process to optimally and reproducibly synthesize monodisperse, nonporous zirconia microspheres (See Figure) by the hydrolysis of zirconium tetra-alkoxides in alcohol solutions in the presence of long-chain carboxylic acids. This invention has been disclosed to the Patent Office of University of Minnesota and a patent application is in progress. The challenge was to produce unaggregated, monodisperse 2 micron diameter spheres that can be used as ultrafast chromatographic materials and essential key developments were crucial. First, they discovered that the reactive gel layer on the particle surface must be removed to avoid the aggregation and polydispersity evident in the previous work (e. g. Lerot et al., J. Mater. Sci., 26 (1991) 2353). Second, they also found two important steps needed to ensure reproducibility: 1) agitation must stopped at a reproducible time, and 2) the reagents must be dry enough (or of reproducible, known dryness) to maintain good control of the particle "appearance" time. Finally, using scanning electron microscopy, confocal fluorescence microscopy and fluoride adsorption uptake measurements, they demonstrated that the microspheres can be sintered to full density thereby removing virtually all pores without inducing aggregation.

Based on the availability of the above nonporous zirconia microspheres, ZirChrom will manufacture a novel family of high performance liquid chromatographic stationary phases including normal phase, reversed phase, anion-exchange and cation-exchange chromatographic materials. These stationary phases will be used for high temperature, ultrafast liquid chromatography at temperatures over 200 °C. For example, silica-based stationary phases, which dominate in high performance liquid chromatography (HPLC), are unstable above 80 °C. Thanks to the fast mass transfer owing to the absence of intrapore diffusion and excellent flow dispersion characteristics, these new stationary phases will lead to 10-fold reduction in hazardous waste that is produced in HPLC. Columns packed with nonporous, carbon clad zirconia will be used to rapidly analyze mixtures including herbicides, insecticides, nitroaromatics, chlorinated phenols, and common caroxylate drugs such as salicylic acid, ibuprofen, and acetaminophen.

This invention will have a major impact on the chemical analysis of an extremely wide variety of materials including environmental toxicants and pharmaceuticals.

This research was supported by National Science Foundation (NSF) SBIR Phase II and National Institutes of Health.