This article describes methods for dissociation of aggregates and antibody-contaminant complexes on hydroxyapatite. The application of decomplexing washes weakens complex stability. Because of its high affinity for apatite calcium, the DNA component of complexes is attracted more strongly to apatite calcium than it is to the antibody. The combination of weakened complexation and strong attraction to apatite calcium apparently allows the apatite to actively extract DNA from the complexes. Once bound to the apatite, DNA cannot rejoin the antibody so that when the antibody is eluted, the DNA remains behind. Whereas conventional application of hydroxyapatite supports effective aggregate removal, the present method dissociates non-covalent aggregates into native antibody. Non-product contaminant complexes are also dissociated and removed more effectively. The method works with both IgG and IgM. Data suggest that host cell DNA fragments are the nucleation centers for antibody aggregate formation…