SizeSep - X is a phase coated with hydrophilic and neutral standing-up monolayer films which chemically bond on porous silica. The bonding chemistry leads to negligible non-specific interactions with great stability. Particle sizes of 3µm and 5µm and pore sizes of 100, 150, 300, 500, 1000, and 2000Å provide typical particle size selection and widest pore size selection for separation and analysis of biological molecules and water soluble polymers in aqueous and water/organic buffers.