Post-detonation recovery of chemical warfare agent simulants using wet swabbing and bulk fragment extraction

Abstract

Reliable, targeted sampling and detection of chemical warfare agent (CWA) residues following explosive dissemination remains a critical challenge in forensic chemistry and chemical incident response. This study integrates controlled detonation experiments with quantitative residue and statistical analysis, demonstrating the importance of matrix-specific and complementary sampling approaches for accurate residue detection. Two physicochemically diverse CWA simulants, methyl salicylate and malathion, as analogues for sulfur mustard (HD) and VX, were applied to steel ball bearings using cotton-polyester fabric or cotton wool across three deposition methods to evaluate their influence on simulant retention following detonation. Residues were quantified by high-performance liquid chromatography (HPLC) to assess both retention and secondary transfer. Results show matrix-dependent residue behaviour, with fabric consistently exhibiting the highest retention of methyl salicylate (up to 6 mg/L), while non-porous materials such as ball bearings and plastic fragments generally retained minimal residues. Container fragments selectively retained malathion more effectively, consistent with differences in physicochemical properties. Secondary transfer was confirmed by the detection of residues on initially uncontaminated fragments. Statistical significance of retention and transfer trends was evaluated using binary logistic regression. Findings demonstrate that matrix characteristics, deposition method, and simulant physicochemistry strongly govern post-blast residue patterns of CWAs. Importantly, residual contamination on fragments remained sufficient to pose transdermal and/or inhalation hazards, given the extreme acute toxicity of VX, which exhibits an oral LD₅₀ of 0.04 mg/kg. Overall, the study provides novel, quantitative insight into post-detonation behaviour, informing forensic sampling strategies, hazard management, and chemical, biological, radiological, and nuclear (CBRN) incident response.