X-ray diffraction of calcined bone tissue: a reliable method for the determination of bone Ca/P molar ratio.

A method is proposed which allows direct measurement by X-ray diffraction of the Ca/P molar ratio in bone tissue after calcination at 900 degrees C. It is based on the construction of a standard curve from known mixtures of hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TP), since these are the only two crystallized mineral phases in the bone ash after its calcination at 900 degrees C. This method, based on physical analysis, may also be used to calculate the respective proportions of calcium and phosphorus after the Ca/P molar ratio has been obtained. It is more sensitive than and at least as accurate as the usual chemical techniques, even though it can be applied to minute samples of bone tissue. Furthermore, the method permits simultaneous determination of lattice parameters and provides additional information about bone mineral structure.