Ancient bone collagen assessment by hand-held vibrational spectroscopy

Radiometric, isotopic, proteomic, and genetic studies of bone collagen are mainstays of archaeometric analysis. All four techniques are destructive and require substantial laboratory, temporal, and financial commitments. Because such analyses are predicated on the presence of a sufficient quantity of unaltered proteins (i.e. collagen), the development and validation of tools for the rapid, non-destructive, in situ analysis of collagen content could yield measurable benefits. In the present work, the results of a preliminary, proof-of-concept study on the utility of four hand-held vibrational spectroscopic instruments, one Fourier-Transform Infrared (FTIR) spectrometer and three Raman spectrometers (two with an excitation wavelength of 785 nm, and one with an excitation wavelength of 1030 nm), for analyzing the collagen content of archaeological bones are described. While the FTIR and 785 nm Raman devices showed little or no ability to discriminate between well- and poorly-preserved bone, the application of hand-held 1030 nm Raman spectroscopy appears to be well-suited for such a task. The ability to detect a measurable and characteristic spectroscopic peak associated with the δCH2 scissoring of Type I collagen in high-yielding, raw bone samples opens the door to the utilization of this technology in field research environments.