Nitrite amperometric sensor for gunshot residue screening

A novel electrochemical sensor comprising a glassy carbon electrode modified with a composite of palladium (Pd) particles and glassy carbon microspheres (GCMs), has been developed to detect gunshot residue via nitrite determination. Pd-GCMs was synthesized through a simple electroless deposition method and characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The electrocatalytic response of nitrite on the Pd-GCMs/GCE is greatly enhanced relative to that on a GCMs/GCE and bare GCE. The applied potential, flow rate and sample volume of flow injection amperometric detection were optimized. The sensor displayed a linear response to nitrite between 0.10 mmol L-1 and 4.0 mmol L-1, with a limit of detection and quantification of 0.030 and 0.11 mmol L-1, respectively. It exhibited very good performance with excellent electrocatalytic activity and high sensitivity (500 +/- 5 mA mM(-1) cm(-2)). In addition, the electrochemical sensor presented good repeatability (RSD < 1.5%, n = 20), reproducibility (RSD = 1.4%, n = 6), and operational stability (RSD = 2.8%, n = 268), along with high sample throughput (165 samples h(-1)). The results of detecting nitrite in gunshot residue with this sensor were in good agreement with those obtained by the Griess method (P>0.05). With its good performance this sensor could be a viable alternative method for detecting nitrite to identify gunshot residue in forensic evaluations via nitrite detection. (c) 2019 Elsevier Ltd. All rights reserved.