Atomic and molecular spectroscopic analysis of chemically treated pig shoulder bone: possible application in forensics

Abstract

Chemical treatment of pig shoulder bone by hydrochloric, hydrofluoric, and acetic acid (0.1 and 1 M) was monitored by FTIR, Raman and LIBS spectroscopy. Fourier deconvolution of FTIR spectra performed in the amide I (1700-1600 cm−1), phosphate (900-1200 cm−1), and carbonate (500-650 cm−1) region indicated the presence of different components in the bone sample, depending on the environment and its concentration. Based on FTIR and Raman spectral data bone samples were characterized by mineral-to-matrix ratio (MM), crystallinity index (CI), and carbonate-to-phosphate ratio. Intensities of calcium ionic-to-atomic spectral lines (364.441 nm and 370.603 nm respectively) obtained from LIBS spectra were used for the estimate of bone hardness. The intensity ratio of phosphorous-to-carbon (P/C) lines was correlated with MM ratios obtained from FTIR spectra. Comparison of FTIR, Raman and LIBS data were in rather good agreement. The results suggest that an increase in acid concentration primarily affects the intensity and the structure of the phosphate band as the phosphate content is more susceptible to demineralization. The highest level of demineralization (the lowest MM), for both concentrations, is obtained for hydrochloric acid, which indicates a greater ability of strong acids to demineralize the inorganic matrix. CI values obtained from Raman spectra (for 0.1 M acid solutions) are in accordance with Ca II/Ca I ratio values obtained from LIBS spectra. Also, MM values obtained from the FTIR spectra are in good agreement with the P/C ratio obtained from the LIBS spectra. These preliminary data motivate further experiments in the field of chemical modifications due to the effects of acids and implications of these processes in forensics.