Multivariate optimisation of ICP OES instrumental parameters for Pb/Ba/Sb measurement in gunshot residues

Abstract

Inductively coupled plasma-optical emission spectrometry (ICP OES) is a powerful analytical tool for the determination of metals. It is simple, fast and inexpensive due to its high sensitivity and versatility, and it can be used to analyse multiple elements. However, its use in forensic chemistry remains underexplored. This study aims to optimise the analysis of gunshot residues (GSRs) by ICP OES using the concentrations of Pb, Ba and Sb released during the firing of ammunition. In this study, experiments were designed using multivariate optimisation to establish the best operating conditions for ICP OES in GSR samples generated from a .38 revolver. Three variables were studied (radio frequency power, nebuliser gas flow and aspiration rate), and the interactions between those variables were investigated using a central composite design to establish the best analysis parameters. The nebuliser gas flow was the most important parameter in the optimization of the signal intensities, and the interactions between the variables were not significant. The optimum values determined for radio frequency power, nebuliser gas flow and aspiration rate were 1300W, 1.2Lmin−1, and 1.0mLmin−1, respectively. After optimisation of the parameters, the performance characteristics of the proposed method were established: linearity, detection and quantification limits, and accuracy (recovery percentage), with and without addition of an internal standard.