Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectral prediction of postmortem interval from vitreous humor samples
- 193 Downloads
Evaluation of postmortem interval (PMI) is of paramount importance to guide criminal investigations, especially when witnesses are not found. However, accurate PMI estimation is a challenging task in the forensic community due to the limitations of existing methods. The study aims to investigate the potential of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy for predicting PMI based on vitreous humor (VH). VH samples were collected from 72 rabbits in the range of 0–48 h postmortem at a 6-h interval. Their FTIR spectra were normalized by the extended multiplicative signal correction (RMSC) and divided into calibration and validation sets. After analysis of the absorption bands, the Bayesian ridge regression (BRR), support vector regression (SVR), and artificial neural network (ANN) methods were established by the calibration set using a 10-fold cross-validation that was further used to predict the PMI in the validation set. The validity of the models was assessed by a permutation test. The current study demonstrated that multiple macromolecules in the VH samples were reflected in a FTIR spectrum, and the spectral absorption bands at 1313 and 925 cm−1 were highly correlated with PMI. The three models allowed generalization to the validation set due to similar R2 and errors between the calibration and validation tests. The highest accuracy with R2 = 0.983 and error = 2.018 h was achieved by the ANN model in the validation test. The results suggest that ATR-FTIR spectroscopy may be useful for VH analysis in order to predict PMI in the future.
KeywordsForensic medicine Postmortem interval Fourier transform infrared spectroscopy Machine learning Vitreous humor
Compliance with ethical standards
The research does not contain any experiments with human participants. All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. The study has been approved by the Ethics Committee of Xi’an Jiaotong University.
Conflict of interest
The authors declare that there are no conflicts of interest.
- 3.Gadzuric SB, Kuzmanovic SOP, Jokic AI, Vranes MB, Ajdukovic N, Kovacevic SZ. Chemometric estimation of post-mortem interval based on Na+ and K+ concentrations from human vitreous humour by linear least squares and artificial neural networks modelling. Aust J Forensic Sci. 2014;46:166–79.CrossRefGoogle Scholar
- 11.Zhang J, Liu L, Mu J, Yang T, Zheng N, Dong H. Chemical analysis in the corpus callosum following traumatic axonal injury using Fourier transform infrared microspectroscopy: a pilot study. J Forensic Sci. 2015;55:3268–75.Google Scholar
- 25.Valderrama P, Braga JW, Poppi RJ. Variable selection, outlier detection, and figures of merit estimation in a partial least-squares regression multivariate calibration model. A case study for the determination of quality parameters in the alcohol industry by near-infrared spectroscopy. J Agric Food Chem. 2007;55:8331–8.CrossRefGoogle Scholar