Reports of the Death of Fully Porous Particles are Greatly Exaggerated

The use of superficially porous silica particles in liquid chromatography dates back to the 1960s. Recently, there has been renewed interest in these particles due to several reports of their lower reduced plate heights as compared to conventional fully porous particles [1-5]. The performance claims of superficially porous particles are briefly reviewed. We demonstrate that the efficiencies and backpressures of 2.1 x 50mm columns packed with 2.6/2.7µm superficially porous particles are very similar to those of columns packed with 2.5µm fully porous particles. We also show that the efficiency of a representative 2.1 x 50mm column packed with 2.7µm superficially porous particles is significantly lower than that of the same size column packed with 1.7µm fully porous particles. We demonstrate the range of selectivities currently available for columns containing fully porous particles, as well as the ability of hybrid organic/inorganic particles (currently only available as fully porous particles) to operate with a wide mobile phase pH range, enabling dramatic changes in selectivity for ionisable compounds. We discuss the benefits of fully porous particles for purification applications and for retaining polar compounds by reversed-phase chromatography. We also demonstrate the excellent performance of columns containing 1.7µm fully porous particles for size exclusion chromatography. These results show that there are several chromatographic goals that may currently only be achieved using modern, fully porous particles.