BIOshell IgG 1000Å C4 is a high-speed, high-performance liquid chromatography column based on a new wide-pore (1000Å) Fused-Core® particle design. The Fused-Core particle provides a thin porous shell of high-purity silica surrounding a solid silica core. This particle design exhibits very high column efficiency due to the shallow diffusion paths in the 0.5-micron thin porous shell and the small overall particle size of 2.7-microns. The densely bonded, extensively endcapped dimethylbutyl stationary phase of BIOshell IgG 1000Å C4 provides a stable, reversed-phase packing that can be used for separating high molecular weight compounds such as proteins.