Analysis of the Ex-vivo transformation of Semen, Saliva and Urine as they dry out using ATR-FTIR spectroscopy and chemometric Approach

The ex-vivo biochemical changes of different body fluids are potential marker for the estimation of TSD. Infrared spectroscopy has great potential to reveal the biochemical changes in these fluids as previously reported by several researchers. Present study is focused to analyze the spectral changes in the ATR-FTIR spectra of three body fluids, commonly encountered in violent crimes i.e., Semen, Saliva and Urine as they dry out. The whole analytical timeline is divided into relatively slow phase I due to major contribution of water and faster Phase II due significant evaporation of water. Two spectral regions i.e., 3200-3400 cm-1 and 1600-1000 cm-1 are the major contributor to the spectra of these fluids. Several peaks in the spectral region between 1600-1000 cm-1 showed highly significant regression equation with higher coefficient of determination values in the Phase II in contrary to the slow passing Phase I. Principal component and Partial Least Square Regression analysis are the two chemometric tool used to estimate the TSD of the aforesaid fluids as they dry out. This study potentially estimates the TSD of an offence at the early stages after is occurrence as well as work as the precursor for further studies on extended timeframe.