A feasibility study of chromatographic methods with mass spectrometry, flame ionization detector ( FID ), and micro electron capture detector ( μECD ) for laboratory adoption of organic gunshot residue analysis at trace levels

This study compares the feasibility of several chromatographic systems, including GC–MS/FID/μECD, GC–MS/MS, and LC–MS/MS for the forensic analysis of trace levels of organic gunshot residue (OGSR). Implementing new methods in forensic laboratories is a complex process fraught with challenges, but it is crucial for keeping pace with technological progress and enhancing the scientific reliability of the evidence. A major obstacle is the significant financial investment required for new equipment, validation, and personnel training. The techniques evaluated here are commonly available in fire debris, explosives, controlled substances, or toxicology units, making the transition to new OGSR services more manageable. This article provides practitioners and laboratory managers with practical recommendations for utilizing popular chromatographic methods for detecting OGSR at trace levels recovered from skin matrices. Figures of merit are reported for six different instrumental configurations for seven analytes of interest: nitroglycerin, 2,4‐dinitrotoluene, diphenylamine, ethyl centralite, 2‐nitrodiphenylamine, Akardite II, and 4‐nitrodiphenylamine. The limits of detection range from 0.3 to 130 ppb, depending on the analyte and method used. Performance rates were calculated for datasets of 20 non‐shooters and 20 shooter samples using various ammunition brands. GC–MS/μECD exhibited superior performance rates, with an average accuracy of 94%, comparable to that of LC–MS/MS. Final reconstitution with hexane improved results when using GC–MS compared with methanol. GC–MS/MS performance rates were slightly lower, with an average accuracy of 87%. These results suggest that adding a secondary detector (μECD) to a GC–MS would allow for a more accessible and sensitive approach to OGSR analysis.