High Retentivity, Lower Column Back Pressure. Widely used octadecyl bonded silica gel enables the Shimpack GIS C18 to have strong hydrophobic interaction and low absorption of ionic compounds. In addition, highly uniform particles ensure stable mobile phase delivery and outstanding low pressure. Shim-pack GIS C18 is ideal for preparative separations. Higher surface area silica and strong retentivity provide high preparative loading capacity without sacrificing peak shape. Bonded Phase: Octadecyl Groups, Particle Size: 2?m, 3?m, 4?m, 5?m, 10?m, Pore Size: 10 nm, Surface Area: 450 m2/g, Carbon Loading: 15%, End-capping: Yes, pH Range: 2 to 7.5, USP Code: L1.