The Changes of Fourier Transform Infrared Spectrum in Rat Brain

Estimation of the time since death (postmortem interval [PMI]) is one of the most difficult problems in forensic investigations, and many methods currently are utilized to estimate the PMI. The goal of this study was to investigate the changes of attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra of rat brain from postmortem time 0-144h. The intensity ratios of major absorbance bands were examined (I ₁₀₆₆/I ₁₃₉₂, I ₁₁₆₈/I ₁₃₉₂, I ₁₂₃₄/I ₁₄₅₄, I ₁₃₀₁/I ₁₃₉₂, I ₁₆₄₇/I ₂₉₅₆, I ₂₉₂₁/I ₂₈₅₀, and I ₁₆₄₇/I ₁₅₃₉). The spectra of rat brain displayed prominent changes with increasing PMI. The band at 2871 and 1737per cm became weak with the time increasing and even disappeared at postmortem 96 and 72h, respectively. A close linear correlation was shown between the relative absorption intensity and the PMI, and the I ₁₂₃₄/I ₁₄₅₄ offered a stronger correlation (r=0.973). Our results indicate that ATR-FTIR spectroscopy may be a useful technique for estimating the PMI.