Control of synthesis conditions to improve zirconia microspheres for ultrafast chromatography

Although it has been known for some time that monodisperse, micrometer-scal e spherical zirconia particles can be synthesized by the hydrolysis of zirc onium alkoxides, the particles so made are frequently aggregated. Moreover, it is not clear whether they can be made nonporous without suffering aggre gation; this would limit their usefulness in applications like ultrafast ch romatography, which require that the particles be spherical and unaggregate d (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 produc tion of microspheres. We clarify important but practical precautions that e asily ensure the reproducibility of the synthesis method. Finally, we demon strate that the microspheres can be made nonporous with a suitable heating schedule.