by Kenneth Ujevich
False positives due to the presence of antimony in vehicle seat fabrics are a problem in gunshot residue (GSR) analysis, in particular, when graphite furnace atomic absorption spectrometry (GFAAS) is employed. This experiment was performed to determine the reason for the false positive results and to propose a new approach for the analysis of GSR on vehicle seats. GFAAS was used to examine adhesive tape swabs collected from 100 seats of 50 different automobiles. Characterization of seat fabrics was carried out by using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy with energy dispersive X-ray specteoscopy (SEM/EDX). The results of FTIR analysis showed that all seat covers containing antimony were composed of polyester. Experimental results obtained by SEM/EDX analysis revealed that the fabrics in these seat covers contained evenly distributed antimony within the structure of the polyester fibers. This study shows that the type of seat fabric should be determined by FTIR spectroscopy before elemental GSR analysis. In this way, most of the false positives caused by polyester fibers in GSR analysis can be prevented, or at least accounted for.
Çağdaş Aksoy, Taner Bora, Nilgün Şenocak, Fırat Aydın. “A new method to reduce false positives due to antimony in detection of gunshot residues.” Forensic Science International, Volume 250, May 2015, Pages 87-90, ISSN 0379-0738, http://dx.doi.org/10.1016/j.forsciint.2015.03.006.