Heat-induced Bone Diagenesis Probed by Vibrational Spectroscopy

Complementary vibrational spectroscopic techniques – infrared, Raman and inelastic neutron scattering (INS) – were applied to the study of human bone burned under controlled conditions (400 to 1000 °C). This is an innovative way of tackling bone diagenesis upon burning, aiming at a quantitative evaluation of heat-induced dimensional changes allowing a reliable estimation of pre-burning skeletal dimensions. INS results allowed the concomitant observation of the hydroxyl libration (OH(libration)), hydroxyl stretching (ν(OH)) and (OH(libration) + ν(OH)) combination modes, leading to an unambiguous assignment of these INS features to bioapatite and confirming hydroxylation of bone’s inorganic matrix. The OH(lib), ν(OH) and ν(4)(PO(4)(3−)) bands were identified as spectral biomarkers, which displayed clear quantitative relationships with temperature revealing heat-induced changes in bone’s H-bonding pattern during the burning process. These results will enable the routine use of FTIR-ATR (Fourier Transform Infrared-Attenuated Total Reflectance) for the analysis of burned skeletal remains, which will be of the utmost significance in forensic, bioanthropological and archaeological contexts.