Multicommutated Anodic Stripping Voltammetry at Tubular Bismuth Film Electrode for Lead Determination in Gunshot Residues

This work describes the construction of a miniaturized flow-through electrochemical cell and its application to the determination of lead in gunshot residues (GSR) by differential-pulse anodic stripping voltammetry at bismuth films co-deposited on-line on a tubular carbon paste electrode. The developed detector was coupled to a multicommutated flow system which was designed to allow medium exchange prior to the stripping step thus reducing interferences from the analytical matrix, and to implement the standard additions method in an automatic way, using only one standard solution. For a deposition time of 60 s at −1.5 V at a flow rate of 0.5 mL min−1 without oxygen removal, the detection limit of the method was 0.2 mg L−1. Under these conditions the linear dynamic range was 0.3–10.0 mg L−1 with a sampling rate of 15.0 samples h−1. Repeatability of lead concentration was 3% (n=3). The method was applied to the analysis of lead in GSR on hands of shooters and concentrations up to 16.5 μg and 6.7 μg were found in palms and backs, respectively. No statistically significant differences between the results obtained by the proposed and the comparative method (F-AAS) were found, at a 95% confidence level.