EFFECT OF INITIAL PH ON HYDROLYSIS OF ALPHA-TRICALCIUM BIS(PHOSPHATE) IN SOLUBILIZED COLLAGEN SOLUTION

The hydrolyzed products of alpha-tricalcium bis(phosphate) (alpha-TCP) formed in solubilized collagen solution for several initial pH's (pH 4 to 8) at 30-degrees-C for 24h were investigated by X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), chemical analysis and so on. For initial pH4 the formation of calcium hydrogenphosphate dihydrate (DCPD) and for initial pH over 5 the formation of hydroxyapatite (HAp) were detected by XRD. Further, it was found from the results of FT-IR that for initial pH 4 a small amount of HAp and octacalcium dihydrogen hexakis (phosphate) (OCP) were formed as hydrolyzed product, and for initial pH over 5 the formation of OCP were observed in addition to HAp. The formation of HAp was at the maximum for initial pH 5, and the amount of HAp in hydrolyzed product obtained in 0.1 mol dm-3 acetic acid-ammonia buff er solution with solubilized collagen was higher than that without collagen. Ca/P molar ratios of the products calculated from the results of chemical analysis were varied from 1.3 to 1.5, which were lower than that of stoichiometric hydroxyapatite (Ca/P=1.67). The processes of the hydrolysis of alpha-TCP, which were suggested by the chemical equations, were explained reasonably by the results of XRD, FT-IR and chemical analysis.