Gelatin-based hydrogels as a novel medium for efficient recovery of organic explosives from post-blast residues: A...

Post-blast residue analysis is critical for forensic investigations, enabling the identification of organic explosives like Trinitrotoluene (TNT), Pentaerythritol tetranitrate (PETN), and 2-Nitrotoluene (2-NT) to reconstruct crime scenes and link perpetrators to illicit activities. Efficient collection of residues from diverse surfaces is essential for accurate forensic analysis, and ensuring justice. Traditional methods, such as cotton swabbing or solvent washing, recover only 50-70 % of residues and are prone to contamination, sample loss, and inefficiency on porous or irregular surfaces. A versatile, eco-friendly medium that enhances recovery across varied substrates is urgently needed. This study explores gelatin-based hydrogels (GHs) as an innovative, biocompatible medium for post-blast residue collection, leveraging their unique adsorbent/absorbent properties for improved surface contact and sampling efficiency in contaminated environments. The research evaluates GHs for recovering TNT, PETN, and 2-NT from ten surfaces spiked with explosive solutions to mimic post-blast residues (e.g., metals, plastics, wood, cloth) using Gas Chromatography-Mass Spectrometry (GC-MS) for qualitative identification. Triplicate experiments demonstrated recovery rates of 80-95 % (mean ± 5 % SD) on non-porous surfaces, and 60-70 % on porous surfaces, including non-precleaned surfaces with contaminants (e.g., dust, soil, oil), validated via ANOVA (p < 0.05). GC-MS confirmed distinct m/z peaks for each explosive (TNT: 210, 193, 180; PETN: 240, 194, 149; 2-NT: 137, 120, 91) with limits of detection of 0.1-0.5 µg/mL and signal-to-noise ratios > 3:1, indicating high sensitivity. Preliminary data suggest GHs may offer cost-effectiveness (∼USD $ 0.50/sample vs. ∼USD $ 2.00 for swabs) and potential field applicability for transport to laboratory settings, significantly improving residue recovery and analytical reliability. This approach enhances forensic capabilities in post-blast investigations and has potential applications in environmental monitoring and homeland security. Future research should validate GHs under real-world conditions and expand their use to other explosives, broadening their forensic utility.