The invention discloses a separation matrix for purification of biological particles, comprising a plurality of particles having a porous core entity and a porous shell entity covering the core entity, wherein the core entity comprises at least 50 micromole/ml primary amines present on covalently attached ligands displaying at least two primary amines per ligand and the shell entity comprises less than 20 micromole/ml primary amines The invention further discloses a method of purifying biological particles and a method of manufacturing a separation matrix.