A preliminary investigation into the comparison of dissolution/digestion techniques for the chemical characterization of polyurethane foam.

Due to their widespread use in domestic and commercial premises, polyurethane foams, as either fragmented or bulk foam, are types of evidence commonly found at crime scenes. The traditional approach to determining the evidential value of polyurethane foam (PF) involves comparing recovered and control fragments under low and high magnification, under various lighting conditions, as well as the comparison of their respective dye spectra. As with most forms of trace evidence, chemical comparison is also desirable. In this work, two approaches to chemically comparing foam fragments were investigated, i.e. inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis of the Tin (Sn) content in different foam types; and gas chromatography-flame ionization detection (GC-FID) analysis of soluble components in PFs mobilized by dichloromethane. Seven different foam types were studied and their Sn content was found to be different. They also produced characteristic GC-FID chromatographic profiles whose compounds were identified with gas chromatography-mass spectrometry (GC-MS) analysis. This study suggests that incorporating chemical data obtained from GC-FID/GC-MS and ICP-OES into a case involving PF could be advantageous, as this will enable the forensic scientist to broaden the comparison between control and recovered fragments, and further assess the strength of the evidence. However, ICP-OES analysis is a destructive technique with a relatively short sample turnaround time, whilst GC-FID analysis is more time-consuming and non-destructive, requiring corroboration with GC-MS data. The values of these two analytical techniques in the forensic chemical characterization of PFs are discussed.

Investigating polyurethane foam as a form of trace evidence.

The aim of this study was to determine whether polyurethane (PU) foam fragments from different sources could be discriminated from each other. Low and high power microscopy was used to determine whether or not foam fragments were distinguishable from each other under various lighting conditions. Once similar foam fragments were declared microscopically indistinguishable, the visible range microspectrophotometer was highly competent in further distinguishing the spectral characteristics in various fragments from each other. Foam fragments from the same source were shown to display no microscopical or chemical variation. Conversely, it was possible to make clear distinctions between foam fragments from different sources.