Control of Synthesis Conditions to Improve Zirconia Microspheres for Ultrafast Chromatography

Although it has been known for some time that monodisperse, micrometer-scale spherical zirconia particles can be synthesized by the hydrolysis of zirconium alkoxides, the particles so made are frequently aggregated. Moreover, it is not clear whether they can be made nonporous without suffering aggregation; this would limit their usefulness in applications like ultrafast chromatography, which require that the particles be spherical and unaggregated (which we term "microspheres") and that they be nonporous. Here we report that when using an alkoxide hydrolysis synthesis process, critical washing steps can eliminate irreversible aggregation and so enable reliable production of microspheres. We clarify important but practical precautions that easily ensure the reproducibility of the synthesis method. Finally, we demonstrate that the microspheres can be made nonporous with a suitable heating schedule.