Using fluorescence analysis to find traces of accelerants in the thermal decomposition products of laminates

Introduction. To enhance combustion in arson attacks, arsonists often use accelerants, or easily accessible petrochemicals, such as gasoline, diesel fuel, as well as their mixtures. As a rule, accelerants are submitted for investigation as traces left on the surface or inside objects of evidence. If objects of evidence are damaged by the fire heat, thermal decomposition products may be formed, and their composition is similar to the one of petrochemicals.

Goals and objectives. The goal of the study is to use fluorescence spectroscopy to study extractive components of the burnt laminate, as one of the most common types of floor coverings, and identify their influence on detec- tion of accelerants.

Methods. The study is focused on extracted samples of the Tarkett laminate, having physical dimensions of 50 × 50 mm2, exposed to the thermal impact in a muffle furnace at the temperatures of 300, 400 and 500°C for 2–10 minutes. The samples were studied using fluorescence spectroscopy at the fluorescence excitation wavelength of 255 nm.

Discussion. The fluorescence spectra of the laminate samples, showing signs of minor thermal damage (color change), include a single wide peak of 300–410 nm with a maximum in the area of 340 – 370 nm. The shift of the fluorescence maximum and the emergence of peaks in other areas of the spectrum are typical for laminate samples, on the surface of which a carbonized layer is formed at the temperature of 300°C (600 s) and 400°C (240, 360 s). An increase in the thermal damage of samples, accompanied by the destruction of the carbonized residue, leads to the decrease in the fluorescence intensity of their extractive components to background values. 

Conclusion. The fluorescence spectra of the laminate samples, obtained by means of burning at 400°C for 240–360 s, have peaks in the area of bicyclic and tricyclic aromatic hydrocarbons, which impede the identifiability of accelerant traces that may be present as heavy oil fractions (oils, lubricants, fuel oil), highly burnt diesel fuels.

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