The use of Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) Spectroscopy in Identifying Trace Amounts of Body Fluids on Varying Surfaces

HILLARY MULLINGS-WILLIAMS

Forensic Biology is a branch of forensics encompassing both serological and DNA analyses. These analyses require biological samples that can be defined as any physical material obtained from any living or deceased subject, including but not limited to blood, saliva, urine, semen. The amount and quality of biological material found at crime scenes may be limited. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) Spectroscopy is a non-destructive method of analyzing and identifying compounds, including in forensic cases. This research also aims to use the nondestructive technique of ATR-FTIR to determine if varying concentrations of body fluids on varying substrates can be accurately identified. Sample of blood and saliva were collected, and serial dilutions of both were placed on coloured and white cotton, linen, and polyester fabrics and coloured and colourless plastic surfaces. The stains were analyzed using the Thermo ScientificTM Nicolet TM iS TM 10 FTIR Spectrometer. The resulting interferograms were interpreted using peak assignment. Substrate studies showed that blood and saliva can be identified, producing unique peaks and spectra, making it possible to differentiate between them. Dilution studies concluded that diluting the body fluids slightly affects the absorbance through a proportional relationship - the lower the concentration, the lower the absorbance. Subtraction of the coloured substrate from the sample containing the bodily fluid can quickly isolate the body fluid, and the presence of colourants and dyes could interfere in identifying blood and saliva on substrates.

Keywords: Attenuated total reflectance Fourier Transform infrared spectroscopy (ATR-FTIR); spectral peaks; body fluids; blood; saliva.