Investigation of columns prepared with monodisperse, solid-core silica particles has shown that an important contribution to their surprising efficiency arises from a very low eddy diffusion (multipath) term in van Deemter plots. The narrow particle size distribution for Fused-Core® silica particles may simply create more uniform column beds and flow paths than particles with broader distribution. Uniform column beds may also preserve initial high efficiency by providing more resistance to voiding and channeling under variable flow and pressure conditions. If small porous silica particles can be made economically with a similar narrow size distribution, they may also allow preparation of columns with higher efficiency and greater bed stability.

Porous silica particles made by usual processes exhibit broad distribution and can be costly to size. A new process has been developed to create silica particles that are highly monodisperse and ready to use for UHPLC. The unique process allows monodisperse silica to be prepared in a range of porosities and sizes with <6% RSD without further sizing. Previously, a size range of 15-25% RSD has been more typical for porous silica particles, even after special sizing procedures have been applied. Results from studies investigating the impact of particle monodispersity in chromatographic processes will be presented. Columns prepared with monodisperse 1.9 µm C18 silica have exhibited more than 300,000 plates per meter for small molecules and greatly enhance the performance of UHPLC instruments.