Evaluation of Instrumental Parameters for Automated Scanning Electron Microscopy/Gunshot Residue Particle Analysis

Computer-controlled analytical scanning electron microscope (SEM) parameters such as the minimum particle size, video threshold, digital clectron beam point spacing, video dwell time, X-ray counting time, and analysis mode, affect the time and accuracy of automated gunshot residue (GSR) particle analysis. The effects of these parameters on automated analysis of a GSR sample are described. This study was performed using custom-written software which includes several features, such as simultaneous energy and wavelength-dispersive X-ray analysis, that are not available in commercial packages. Proper setting of the backscattered electron (BSE) video threshold is critical for automated SEM/GSR particle analysis. Use of a calibrated BSE detector facilitates reproducible setting of the BSE video threshold. With the results from this and similar studies using different GSR samples, it should be possible to develop standard procedures for automated SEM/GSR particle analysis.