ATR FT-IR Spectroscopy: A Novel and Non-Destructive Approach for the Detection of Blood on a Single Fiber

Abstract

Blood is often encountered on different types of substrates in criminal investigations. Among such substrates, blood stained fabrics are one of the most commonly encountered evidence. Analysis of bloodstains on fabrics is restricted due to interference of fabric dyes, color of fabric which hampers visual identification, and limited sample quantity. Over the years, a plethora of research has been conducted to analyze recovered blood traces, however, the methods employed are limited by factors such as sample destructibility, chronophagus processing, and vulnerability to false positive results. To circumvent the aforementioned limitations, use of ATR FT-IR spectroscopy has surged as a non-destructive and reliable tool for the detection of traces of blood and other body fluids on fibers. In the present study, an attempt has been made to detect traces of blood in fibers of different types and colors using ATR FT-IR spectroscopy. The obtained results unequivocally concluded that by using ATR FT-IR spectroscopy blood can be successfully detected even on a single fiber through characteristic peaks positioned at 1650 cm-1 and 1543 cm-1 corresponding to amide I and amide II. On the basis of the IR marked protein region (1700-1500 cm-1) bloodstains could easily be discriminated from the blank fibers (except human hair, which overlapped with the peaks of bloodstained fibers) by using PCA chemometric tool. Although, further investigations are needed to be conducted, this proof-of-concept study establishes the potential use of ATR FT-IR spectroscopy for the non-destructive, rapid, eco-friendly, and reliable identification of blood traces from a single fiber due to its inherent surface sensitivity and smaller penetration depth.