Analysis of gunshot residues produced by .38 caliber handguns using inductively coupled plasma-optical emission spectroscopy (ICP OES)

A new analytical method is proposed for the collection and quantification of gunshot residues (GSRs) from firearms using inductively coupled plasma optical emission spectrometry (ICP OES). Lead (Pb), barium (Ba) and antimony (Sb) concentrations in GSR from .38 caliber Taurus® handguns were monitored, and three important methodologies were evaluated such as: i) the collection region of the hand of the shooter; ii) tape-type versus swab collectors; and iii) GSR quantification from the right and left hands. Pb, Ba and Sb were found in four of the hand regions analyzed (palm, back, thumb and forefinger palm (TF-palm), and thumb and forefinger back (TF-back)), with their concentrations increasing as a function of the number of shots (one, three and five). Lead was found to be the most abundant species present. In terms of relative analytical sensitivity, higher concentrations of these three elements are mainly found in the back, TF-palm and TF-back regions. The effect of hand washing was also evaluated, which the TF-palm and the TF-back regions maintained sensitivity for the detection of three elements (concentrations higher than 4.56 μg L− 1) for only three and five shots. Among the collection devices analyzed, swab collectors (dry, moistened with EDTA, and moistened with water) presented higher sensitivity than tape-type collectors (adhesive, double-sided and adhesive-plaster). Additionally, swabs are a more economical collection device, providing a simple and fast collection method that does not require microwave digestion. Pb, Ba and Sb concentrations were also evaluated on the left and right hands. It was observed that Pb is mainly found on the right hand, whereas Ba and Sb concentrations are similar on both hands. ICP OES is therefore a powerful tool for GSR analysis, providing multielemental quantification of Pb, Ba and Sb.