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Rapid and Nondestructive Forensic Identification of Tire Particles by Attenuated Total Reflectance – Fourier Transform Infrared Spectroscopy and Chemometrics

Abstract It is of great significance to realize the rapid, nondestructive and accurate identification of tire rubber particles in forensic science. However, there are no relevant reports. This study collected and tested infrared spectroscopy data of 240 samples from 15 brands. Baseline correction, multivariate scatter correction, standard normal variables and Savitzky-Golay smoothing were adopted to preprocess the infrared spectra. The comparison of the fingerprint region and full infrared spectrum was explored. The identification models were established by principal component analysis and discriminant analysis. The results showed that there is no significant discrimination in the peak position and shape; instead the peak intensity and relative height were slightly different. The cumulative variance contribution rate of principal components 1 through 12 reached 98.3690% demonstrating 98.3690% of the details in the original measurements. The 39-dimensional principal components of infrared fingerprint region accurately differentiated sample brands and employed computational complexity. Styrene butadiene samples from six brands were accurately identified based on the three discriminant functions Za1, Zb1, and Zc1. Butadiene samples from five brands were differentiated using discriminant functions Za2, Zb2, and Zc2. Isoprene samples from brands were separated using the discriminant functions Za3, Zb3, and Zc3. All samples were precisely identified by this rapid and nondestructive protocol. The results of this study demonstrate the potential of attenuated total reflectance-Fourier transform infrared spectroscopy in combination with principal component analysis and discriminant analysis as a new method for the identification of tire rubber particles.