Behavior of Dopant Ions in the Solution Synthesis of Substituted Calcium Phosphates

The dependence of (Zn, Cu, Co, Ni, Mn)-substituted calcium phosphates on the synthesis method was studied. The phosphates were synthesized by precipitation from aqueous solution and by mechanoactivation-assisted heterophase synthesis. Phosphates with metal : phosphorus ratios of 1.5 and 1.67 were obtained, which are precursors of tricalcium phosphate and hydroxyapatite, respectively. The obtained samples were studied by AES-ICP and flame AAS. The contents of Zn, Cu, Co, Ni, and Mn in the samples and the mother liquors were quantitatively determined. It was found that the contents of Cu 2+ , Zn 2+ , Co 2+ , and Ni 2+ ions in the phosphates are greatly underestimated in comparison with the calculated amounts introduced in the synthesis. Meanwhile, for tricalcium phosphate, precipitation from solution and the heterophase synthesis gave comparable values of the contents of the dopant ions. At the same time, the heterophase synthesis of substituted hydroxyapatites increases the content of the dopant ion in the product by ~48%.