Comparative spectroscopic characterization of ignitable liquid residues and fire debris using FTIR and XRD

Ignitable liquid residues (ILRs) and combustion-derived fire debris are critical evidence in arson investigations, yet substrate-derived pyrolysis products often complicate accelerant identification. This study comparatively characterized ignitable liquid residues and representative fire debris substrates using Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffractometry (XRD) to generate preliminary spectroscopic information relevant to fire investigations in Ghana. Gasoline, diesel, kerosene, turpentine, and paint thinner, together with biomass-based, polymeric, and electrical substrates, were combusted under controlled laboratory conditions. FTIR analyses revealed characteristic absorptions at approximately 1701 cm−1 (C = O stretching), 1578–1509 cm−1 (aromatic C = C vibrations), 2950–2850 cm−1 (aliphatic C–H stretching), and 1000–1100 cm−1 (C–O stretching associated with cellulose-derived products). Nylon and electrical materials exhibited additional absorptions near 3345–3353 cm−1 attributable to N–H/O–H vibrations. XRD analyses indicated predominantly amorphous carbonaceous soot with additional crystalline diffraction features. The results demonstrate significant substrate-induced spectral interference and provide preliminary spectroscopic information that may support future nondestructive fire debris characterization and arson investigations in resource-limited forensic laboratories.