A chromatography medium comprising porous beads having an inner porous core and an outer porous shell is used for chromatographic separation of enveloped or membranous biological particles from impurities such as contaminant DNA and/or protein. The core is capable of binding molecules via hydrophobic interactions; however, the pore size of the shell does not allow particles having a size of 20 nm and larger to permeate into the bead and interact with the core. The separation is performed at a pH of less than 7.4. The enveloped or membranous biological particles may have been subjected to a prior chromatographic capture step. When used for purification of enveloped virus particles the inventive process was found to yield a remarkably high rate of infectious virus particles.

A chromatography medium comprising porous beads having an inner porous core and an outer porous shell is used for chromatographic separation of enveloped or membranous biological particles from impurities such as contaminant DNA and/or protein. The core is capable of binding molecules via hydrophobic interactions; however, the pore size of the shell does not allow particles having a size of 20 nm and larger to permeate into the bead and interact with the core. The separation is performed at a pH of less than 7.4. The enveloped or membranous biological particles may have been subjected to a prior chromatographic capture step. When used for purification of enveloped virus particles the inventive process was found to yield a remarkably high rate of infectious virus particles.