Far-Infrared Absorption Properties of Bone-Related Calcium Phosphates

Phase identification in bones is necessary in understanding the complex bone mineralization process. One technique that is employed in bone classification is infrared spectroscopy. However, most previous reports have focused on the mid-infrared region. It is then interesting to investigate bone components at far-infrared frequencies to find possible unique characteristics that could be useful in bone classification. In this study, we present the far-infrared/terahertz absorption properties of synthetic forms of the principal compounds involved in bone mineralization—hydroxyapatite (HAp) and octacalcium phosphate (OCP)—measured by Fourier transform infrared spectroscopy. We found unique absorption peaks of HAp and OCP at 2.9 and 3.3 THz, respectively. These findings could be useful in bone composition analysis using far-infrared/terahertz spectroscopy that can complement other methods.