An octacalcium phosphate intermediate in the synthesis of chromatographic hydroxyapatite

In the laboratory synthesis of hydroxyapatite for liquid column chromatography different procedures give varying amounts of a transient intermediate, identified by X-ray diffraction as octacalcium phosphate. The intermediate is most abundant in a recently-developed method involving conversion from brushite at neutral pH; well-crystallized hydroxyapatite is then produced without the boiling previously found necessary. The results are relevant to hydroxyapatite biosynthesis, where a similar intermediate has been postulated. Methods are described for the laboratory synthesis of octacalcium phosphate.