Investigation on synthesis of spheres-on-sphere silica particles and their assessment for high performance liquid chromatography applications

There is a continuing challenge in improving the separation speed while keeping both the resolution high and the back pressure low in high performance liquid chromatography (HPLC). The recent renaissance of core–shell (or fused-core) silica particles has shown great promise in this respect. However, the fused-core silica particles are typically synthesized by the time-consuming multiple-step layer-by-layer technique. An one-pot synthesis of spheres-on-sphere (SOS) silica microspheres is presented here. The preparation parameters including Si precursors, mixing methods (magnetic stirring, mechanical stirring and homogenization), heating (microwave heating and conventional heating), and reaction temperature are investigated in order to control the morphology and improve the size distribution of the SOS particles. The improvement and influence on SOS morphology, particle size and particle size distribution are discussed. Furthermore, the calcined and modified SOS particles are packed into stainless steel columns, which are then assessed for the separation of various test mixtures containing small molecules and proteins under normal phase, reversed phase, and HILIC conditions. The HPLC tests demonstrate fast and efficient separation with very low back pressure, suggesting that SOS particles are a type of new and highly promising packing materials for liquid chromatography.