Ultra High Retentivity Ideal for Separation of Basic Molecules & its Related Substances, Process Impurities. The GL Sciences High-Density Bonding of C18 Phase Delivers Alternative Selectivity to conventional C18 Columns. Physical Properties: Silica: 3 Series High Purity Silica Gel Particle Size: 3 μm, 5 μm Surface Area: 450 m2/g Pore Size: 100 Å (10 nm) Pore Volume: 1.05 mL/g Bonded Phase: Octadecyl Groups End-capping Yes Carbon Loading: 23 % pH Range: 2~7.5 USP Code: L1 More information is available on the GL Sciences website.