Forensic Workflow for Residue Recovery from Oversized Post-Blast Exhibits in ANFO Detonations

Forensic Workflow for Residue Recovery from Oversized Post-Blast Exhibits in ANFO Detonations | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Forensic Workflow for Residue Recovery from Oversized Post-Blast Exhibits in ANFO Detonations D KUMAR, NIRANJAN BALIARSINGH, SOUJANYA GOWNENI This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8421591/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: Post-blast forensic investigations frequently involve oversized debris such as concrete and metallic fragments, where heterogeneous residue distribution and complex surface matrices complicate explosive residue recovery. Conventional extraction techniques optimized for small and homogeneous samples often prove inadequate for such exhibits, resulting in reduced sensitivity and interpretative uncertainty. This study addresses these challenges by developing and validating an integrated residue recovery workflow specifically tailored for oversized post-blast exhibits associated with ammonium nitrate fuel oil (ANFO) detonations. Results: Oversized exhibits were examined using a combined approach incorporating sequential solvent swabbing, spatial subsampling, and syringe filtration. Organic residues were analyzed by thin-layer chromatography (TLC) and gas chromatography–mass spectrometry (GC–MS), while inorganic residues were characterized using classical chemical spot tests and Fourier-transform infrared (FTIR) spectroscopy. GC–MS analysis confirmed the presence of high-boiling petroleum hydrocarbons consistent with diesel fuel fractions, and inorganic analyses identified nitrate-based oxidizers, including ammonium and potassium nitrate. Chlorates, perchlorates, and metallic additives were not detected. Spatial subsampling improved trace residue recovery from heterogeneous surfaces, while syringe filtration significantly reduced background interference and enhanced analytical clarity. Conclusion: The integrated workflow demonstrated reliable and reproducible recovery of both organic and inorganic ANFO residues from oversized post-blast debris. The combined application of spatial subsampling, sequential swabbing, and syringe filtration enhanced analytical sensitivity and forensic interpretability in complex detonation scenarios. This validated approach provides a practical and adaptable framework for forensic laboratories handling large, heterogeneous post-blast exhibits and strengthens the chemical basis for reconstructing ANFO-related explosive events. Post-blast analysis Oversized exhibits ANFO GC–MS FTIR Explosive residue analysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction The forensic investigation of explosive incidents plays a critical role in event reconstruction, identification of explosive formulations, and judicial proceedings. Ammonium nitrate fuel oil (ANFO) remains one of the most frequently encountered improvised explosives due to its widespread availability, low cost, and high detonation efficiency [ 1 , 2 ]. Following detonation, explosive residues are dispersed onto a wide range of substrates, including soil, metals, plastics, and concrete. Oversized and irregular debris presents additional analytical challenges because residue deposition is often uneven, resulting in pronounced surface contamination gradients [ 3 ]. Conventional residue recovery techniques, such as swabbing and solvent rinsing, are routinely applied in forensic casework. However, these methods are primarily optimized for small and relatively uniform exhibits and often yield poor recovery when applied directly to large, heterogeneous post-blast debris [ 4 ]. To address these limitations, adaptations such as spatially resolved subsampling, improved filtration, and optimized solvent extraction strategies have been proposed (Fig. 1 ) [ 5 ]. Analytical techniques remain central to post-blast residue characterization. Gas chromatography–mass spectrometry (GC–MS) provides reliable detection of organic explosive components and fuel oils, while Fourier-transform infrared (FTIR) spectroscopy and classical chemical spot tests are widely used for the identification of inorganic oxidizers and ions [ 6 , 7 ]. The effectiveness of these techniques, however, is strongly dependent on the efficiency of the initial sampling and extraction procedures. While recent advances in chemosensors and molecular frameworks have demonstrated high selectivity for nitroaromatic explosives under controlled conditions [ 12 , 13 ], such approaches are generally unsuitable for complex and contaminated post-blast debris. Comprehensive reviews, including the INTERPOL survey on explosives analysis, highlight the lack of validated workflows for heterogeneous and oversized exhibits and emphasize contamination control as a critical factor in forensic reliability [ 14 ]. The present study addresses this gap by developing and validating an integrated forensic workflow—combining sequential swabbing, solvent extraction, syringe filtration, and spatial subsampling with complementary analytical techniques—specifically tailored for oversized ANFO-related post-blast exhibits. 2. Materials and Methods 2.1. Exhibits Received for Examination Oversized metallic, plastic, and soil fragments were received for forensic examination from the investigating authority following a post-blast incident involving an ANFO detonation. The exhibits comprised large metal fragments measuring up to 29 inches in length, spades, metallic pots approximately 12 inches in height, a cardboard drum, and a deformed metallic cover (Fig. 2 ). Control soil samples were collected from unaffected areas in the vicinity of the blast site to serve as negative controls. All exhibits and control samples were packaged individually in clean, sealed containers to prevent cross-contamination during handling and transport [ 16 – 18 ]. 2.2. Residue Recovery and Spatial Subsampling Strategy Residues were recovered from oversized post-blast exhibits using a structured residue recovery approach based on sequential swabbing. Cotton applicators were moistened with analytical-grade solvents and applied in a defined sequence—diethyl ether, acetone, deionized water, sodium hydroxide solution, and pyridine—to preferentially extract non-polar organic residues followed by polar organic and inorganic components. Swabbing was performed systematically across all accessible surfaces of each exhibit to ensure comprehensive coverage. The collected swabs were extracted into clean glassware, and the combined extracts were filtered through 0.22 µm nylon syringe filters to remove particulate matter and minimize matrix-related interference. The filtrates were subsequently concentrated at room temperature to a final volume of approximately 2–5 mL prior to instrumental analysis [ 10 , 11 , 16 – 18 ]. Oversized post-blast exhibits frequently exhibit highly heterogeneous residue distribution as a result of uneven deposition, secondary fragmentation, and surface-specific adsorption processes. To address this variability, a spatial subsampling strategy was implemented in which large exhibits were systematically divided into discrete surface regions based on geometry, exposure orientation, and visible blast effects. Each region was independently swabbed and extracted rather than combined into a single composite sample, thereby reducing dilution of localized residue hotspots and increasing the probability of recovering trace-level explosive components from contaminated or weathered surfaces (Fig. 3 ). In addition, spatial subsampling enabled comparative assessment of residue distribution across different areas of the same exhibit, providing valuable contextual information for forensic interpretation. When integrated with sequential swabbing and syringe filtration, this approach significantly enhanced analytical sensitivity, reproducibility, and interpretative reliability for heterogeneous and oversized post-blast debris associated with ANFO detonations. 2.3. Analytical Workflow A schematic overview of the integrated analytical workflow is shown in Fig. 4 based on the standard laboratory protocols [ 9 ]. Organic residue analysis : Ether and acetone extracts were examined using thin-layer chromatography (TLC) on silica gel plates, employing chloroform/acetone (1:1, v/v) and toluene/cyclohexane (7:3, v/v) as mobile phases. Visualization was carried out under UV light (254 nm) and by chemical spraying. Confirmatory analysis was performed using GC–MS for the detection of fuel-oil hydrocarbons and high explosives [ 8 – 11 ]. Inorganic residue analysis Water and sodium hydroxide extracts were subjected to classical chemical spot tests for common anions and cations, including nitrate, nitrite, ammonium, and potassium. Selected extracts were further characterized using FTIR spectroscopy. Filtration assessment The effect of syringe filtration on analytical clarity and background interference was evaluated by comparing filtered and unfiltered extracts during GC–MS analysis [ 16 – 18 ]. 2.4. Instrumental Parameters GC–MS : Analyses were carried out with an electron ionization (EI) source at 70 eV, full-scan mode (m/z 40–500), on a 30 m × 0.25 mm × 0.25 µm capillary column. The oven program ramped from 100°C to 280°C with controlled heating rates. Compounds were identified by comparison with NIST library spectra. Table 1 briefs the parameters of the GC-MS method.[ 8 – 11 ] TLC : Developed plates were visualized under UV (254 nm) and by spraying with diphenylamine and sulfuric acid reagents. [ 8 – 11 ] FTIR : ATR-FTIR spectra were recorded from 4000–400 cm⁻¹ at 4 cm⁻¹ resolution; spectral matching was performed using instrument libraries. [ 8 – 11 ] Table 1 Parameters of the GC-MS Method MS transfer line temperature [°C] 250 Ion source temperature [°C] 250 Total Run time [min] 6.250 Inlet Temperature [°C] 230 Carrier Flow [ml/min] 1.000 GC Oven Temperature Nominal Start at 100.0°C hold for 0.2 min Ramp to 220°C at 30°C/min Hold for 0.3 min at 220°C Ramp to 280°C at 80°C/min Hold for 1 min at 280°C °C - degree Celsius, min-minutes 2.5. Quality Control Procedural blanks (blank swabs) and negative control samples (control soil) were processed concurrently with questioned exhibits to assess potential environmental and laboratory-derived contamination throughout all stages of the analytical process. Certified reference materials and laboratory standards of commonly encountered explosives and explosive components, including RDX, TNT, PETN, and ANFO constituents, were analyzed under identical instrumental and procedural conditions to support analytical verification and result interpretation. The inclusion of negative controls and reference materials as part of routine quality assurance and quality control measures is consistent with INTERPOL-recommended best practices and ASTM guidance for the forensic examination of explosives and explosive residues, which emphasize contamination monitoring, method validation, and interpretive reliability as essential elements of forensic reporting [ 14 ]. 2.6. Challenges in the Analysis of Oversized Exhibits Extraction from the exhibits of smaller sizes and their debris is possible by rinsing the exhibit with a minimum quantity of solvent in a beaker. In this method, the ingredients of the unexploded and exploded explosives can be easily collected from the exhibits by dissolution. In contrast, oversized exhibits cannot be conveniently immersed or rinsed, making swabbing the primary viable recovery method. Factors such as cotton quality, operator variability, solvent loss, and inefficient transfer of residues from the swab can affect recovery efficiency. Careful and systematic swabbing, combined with filtration and complementary analytical techniques, is therefore essential to minimize analytical uncertainty. 3. Observations 3.1. TLC and GC-MS Examinations GC–MS analysis of ether extracts revealed the presence of high-boiling petroleum hydrocarbons. Hexadecane was identified at a retention time of 14.02 min, with a similarity index (SI) of 792 and a reverse similarity index (RSI) of 929 based on NIST library matching. The corresponding total ion chromatogram (TIC) is shown in Fig. 5 . No high explosives were detected in acetone extracts by TLC or GC–MS. [ 16 – 18 ] The mass spectra of the forensic case sample obtained by analysis using the GC-MS method, along with the reference library of mass spectra, are shown in Fig. 6 . The x axis presents abundance and y axis presents m/z values.[ 16 – 18 ] 3.2. Chemical Examinations Chemical examination of water, alkaline, and pyridine extracts yielded positive results for nitrate, nitrite, ammonium, potassium, chloride, sulfate, and elemental sulfur in the questioned exhibits. Chlorate, perchlorate, and metallic additives such as aluminium and magnesium were not detected. Observations are summarized in Table 2 .[ 16 – 18 ] Table 2 Observations of the Chemical Examinations Sl.No Chemical Test Target Ion/Analyte Observation 1 Silver Nitrate Chloride Present 2 Griess Test Nitrite Present 3 Griess reagent + Zn dust Nitrate Present 4 Aniline sulphate Chlorate Absent 5 Methylene blue indicator Perchlorate Absent 6 Barium chloride Sulphate Present 7 Zinc Uranyl Acetate Sodium Absent 8 Sodium Cobaltinitrate Potassium Present 9 Nessler’s reagent Ammonium Present 10 Magneson-I Magnesium Absent 11 Sodium Rhodizonate Barium, Calcium, Strontium Absent 12 Sodium Nitroprusside Sulphide (NaOH Extract) Absent 13 Alizarine-S Metallic Aluminium (NaOH Extract) Absent 14 Gutzeit’s Test Arsenic (NaOH Extract) Absent 15 Pyridine + NaOH Elemental Sulphur Present 3.3. FTIR Analysis FTIR analysis of aqueous extracts confirmed the presence of nitrate-based oxidizers. Reference spectra of ammonium nitrate and potassium nitrate were used for comparison. Both oxidizers were detected across different extracts, indicating heterogeneous residue distribution on oversized exhibits. Representative spectra are shown in Figs. 7 and 8 .[ 16 – 18 ] 4. Results 4.1. Organic Residue Detection (GC–MS and TLC) GC–MS analysis of ether extracts confirmed the presence of high-boiling petroleum hydrocarbons, with hexadecane detected at a retention time of 14.02 min (Fig. 6 ). This compound is characteristic of diesel oil fractions and supports the presence of fuel oil components consistent with ANFO formulations. The mass spectral profile exhibited a high similarity match with the NIST library, indicating reliable compound identification (Fig. 6 ). No high-explosive compounds were detected in acetone extracts by either TLC or GC–MS analysis, suggesting the absence of secondary high-explosive admixtures within the recovered residues. 4.2. Inorganic Residue Detection by Chemical Tests Chemical spot tests yielded positive responses for nitrite, nitrate, ammonium, chloride, potassium, sulphate ions, and elemental sulphur across multiple post-blast exhibits (Table 2 ). Tests for chlorate, perchlorate, and metallic additives such as aluminium and magnesium were negative. These results are consistent with nitrate-based low explosive residues typically associated with ANFO formulations. 4.3. FTIR Characterization of Post-Blast Inorganic Oxidizer Residues FTIR spectroscopy was employed to characterize inorganic oxidizer residues recovered from oversized post-blast exhibits. Spectra obtained from questioned samples were compared with laboratory reference spectra of ammonium nitrate and potassium nitrate. This variation reflects spatial heterogeneity, with ammonium nitrate detected in some subsamples and potassium nitrate predominating in others The ammonium nitrate reference spectrum exhibited a broad N–H stretching band at approximately 3392 cm⁻¹, along with characteristic absorptions at ~ 1636 cm⁻¹ (ammonium bending) and a strong nitrate asymmetric stretching band at ~ 1322 cm⁻¹. Additional nitrate-related absorptions were observed at ~ 1045 cm⁻¹ and ~ 820 cm⁻¹, with lattice vibration bands below 600 cm⁻¹. In contrast, the questioned post-blast samples lacked the ammonium N–H stretching feature near 3400 cm⁻¹ and displayed a dominant absorption at ~ 1364 cm⁻¹, characteristic of nitrate asymmetric stretching in alkali metal nitrates. Additional absorptions at ~ 953 cm⁻¹, ~ 823 cm⁻¹, and multiple bands within the 730–560 cm⁻¹ region were consistent with potassium nitrate. The absence of ammonium-specific bands supported exclusion of ammonium nitrate as the primary oxidizer in these subsamples. 4.4. Workflow Performance in Oversized Exhibits Sequential swabbing followed by solvent extraction and syringe filtration resulted in improved extract clarity and enhanced analytical performance. Syringe filtration effectively reduced particulate interference and background noise during GC–MS analysis, as reflected by improved chromatographic resolution (Fig. 6 ), facilitating reliable detection of trace-level residues [ 4 ]. Spatially resolved subsampling (Fig. 3 ) further contributed to improved recovery from heterogeneous surfaces, minimizing dilution of localized residue hotspots. 5. Discussion 5.1. Forensic Interpretation of Analytical Findings The combined recovery of petroleum hydrocarbons and nitrate salts confirms the ANFO origin of the post-blast residues and is consistent with molecular fingerprints reported for ANFO detonations in technical reference studies [ 15 ]. The identification of diesel-range hydrocarbons by GC–MS (Fig. 6 ), together with nitrate-based inorganic residues detected by chemical tests (Table 2 ) and FTIR spectroscopy (Fig. 7 ), provides complementary and mutually reinforcing evidence supporting device composition and formulation. Compared with prior studies employing molecular frameworks and chemosensors for selective detection of nitroaromatic explosives [ 12 , 13 ], the present workflow directly addresses the analytical challenges posed by large-scale, heterogeneous, and environmentally contaminated post-blast debris. While sensor-based approaches demonstrate high selectivity under controlled laboratory conditions, their applicability to mixed and contaminated post-blast matrices remains limited. In contrast, the integrated methodology described here—incorporating spatial subsampling (Fig. 3 ), sequential solvent swabbing, syringe filtration, and complementary analytical techniques—provides a robust and adaptable framework for forensic examination of oversized exhibits. FTIR spectroscopy proved particularly valuable as a rapid screening tool for differentiating between ammonium-based oxidizers and alkali metal nitrates (Fig. 7 ), thereby guiding subsequent confirmatory analyses and contextual interpretation. Overall, the workflow enhances analytical sensitivity, improves reproducibility, and strengthens evidentiary reliability, extending forensic capability in the investigation of complex ANFO-related detonation scenarios involving oversized post-blast debris. 6. Conclusion This study demonstrates that tailored forensic workflows are essential for the reliable analysis of oversized post-blast exhibits. By integrating sequential swabbing, solvent extraction, syringe filtration, and spatial subsampling with complementary analytical techniques, both organic (fuel oil hydrocarbons) and inorganic (nitrate-based) residues were detected with high confidence. Syringe filtration was particularly effective in maximizing recovery and reducing analytical interference, while multi-method corroboration strengthened evidentiary interpretation. These findings confirm the exclusive use of ANFO in the investigated detonation and highlight the broader significance of adapting forensic protocols to heterogeneous, large-scale evidence. Beyond the present case, the validated workflow provides a generalizable framework that enhances evidentiary reliability and strengthens the chemical basis for reconstructing complex detonation events. Abbreviations The following abbreviations are used in this manuscript: TLC Thin Layer Chromatography GC-MS Gas Chromatography Mass Spectrometry FTIR Fourier Transform Infrared Spectroscopy in. inches TIC Total Ion Chromatogram NIST National Institute of Standards and Technology AR Analytical Reagent ATR Attenuated Total Reflectance ANFO Ammonium Nitrate Fuel Oil PETN Penta Erythritol Tetra Nitrate TNT Tri Nitro Toluene RDX Research Department Explosive/ Royal Demolition Explosive TETRYL Trinitrophenylmethylnitramine HMX High Melting Explosive - Octogen UV Ultra Violet NaOH Sodium Hydroxide Declarations Ethics approval and consent to participate Not applicable Consent for publication All authors have reviewed, revised, and approved the final manuscript for submission. Clinical trial number Not applicable Funding None Author Contribution Conceptualization, D.K.; methodology, D.K.; validation, D.K.; formal analysis, D.K.; investigation, D.K.; writing—original draft preparation, D.K., N.B., S.G.; writing—review and editing, D.K., N.B., S.G.; visualization, D.K., N.B., S.G.; and supervision, D.K. All the authors have read and agreed to the published version of this manuscript. Acknowledgement I would like to express my gratitude to the Director, Central Forensic Science Laboratory, Pune and Hyderabad, for continuous support and for providing the necessary infrastructure for this study. Data Availability The author declares that the data supporting the findings of this study are available within the paper. Should any raw data files be needed in another format, they are available from the author upon reasonable request. 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05:33:31","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":24499,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/f1b664668ded16e38744d10a.png"},{"id":98977658,"identity":"70a36fd2-f2e1-4187-9d4f-f24b8734a364","added_by":"auto","created_at":"2025-12-25 05:33:31","extension":"xml","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":61553,"visible":true,"origin":"","legend":"","description":"","filename":"577cd3ad5bff448dbd8a4d8fba9c9f5b1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/d32eea763bbe453f997e85ff.xml"},{"id":98977664,"identity":"997a1b33-72ac-4779-8772-09ddab7f8274","added_by":"auto","created_at":"2025-12-25 05:33:31","extension":"html","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":70152,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/8f7d8da65bce4bd710a791a4.html"},{"id":98977644,"identity":"415c44f7-2eb0-4b74-942e-bd10729b5c3b","added_by":"auto","created_at":"2025-12-25 05:33:31","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":94754,"visible":true,"origin":"","legend":"\u003cp\u003eForensic Workflow for Oversized Exhibits Examination\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/5255df4c8dc24cd3dbc62e8c.jpeg"},{"id":99311694,"identity":"23b0c300-8363-4887-8eeb-455b75bd167b","added_by":"auto","created_at":"2025-12-31 16:16:30","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":684027,"visible":true,"origin":"","legend":"\u003cp\u003eOversized Exhibits collected from the Crime Scene\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/93b507e57378e944325031f5.png"},{"id":99312183,"identity":"abcab2fd-28fe-4955-9c37-f78605ddcad6","added_by":"auto","created_at":"2025-12-31 16:18:14","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1249423,"visible":true,"origin":"","legend":"\u003cp\u003eSpatial subsampling strategy\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/587689078bb3867b2fdaf350.png"},{"id":98977659,"identity":"48134c1c-ffb9-4774-91f1-47ad0927191f","added_by":"auto","created_at":"2025-12-25 05:33:31","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":217997,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram for Post-Blast Explosive Analysis\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/c4f1f9467cffcfd2d6b8782f.png"},{"id":98977646,"identity":"6da39361-1aed-4486-8e30-3966da1cb743","added_by":"auto","created_at":"2025-12-25 05:33:31","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":71953,"visible":true,"origin":"","legend":"\u003cp\u003eTIC of the exhibit having hydrocarbons\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/5ee676e91a8979ee131be043.png"},{"id":98977662,"identity":"e2566e52-5f30-4d42-b99d-60d7dead14ff","added_by":"auto","created_at":"2025-12-25 05:33:31","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":113110,"visible":true,"origin":"","legend":"\u003cp\u003eMass spectrum of the Extract (Top) and its NIST library (Bottom)\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/da516384b527188cc5181c57.png"},{"id":98977649,"identity":"068f37df-d649-4231-95f4-233710d0a99e","added_by":"auto","created_at":"2025-12-25 05:33:31","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":65514,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectrum of Potassium Nitrate\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/704ef5db5ca8697b6ea00d12.jpeg"},{"id":98977654,"identity":"5c85e0d5-1721-4ea9-a0f5-e435c715cad2","added_by":"auto","created_at":"2025-12-25 05:33:31","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":62625,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectrum of Ammonium Nitrate\u003c/p\u003e","description":"","filename":"floatimage8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/bf6c26799044d636009a0b58.jpeg"},{"id":100356074,"identity":"eb9e74aa-0b05-4484-bb9c-d9ad88b5a8f2","added_by":"auto","created_at":"2026-01-16 06:49:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3683466,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8421591/v1/062b5ce7-13af-4aee-a526-eabb4ffc99a6.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Forensic Workflow for Residue Recovery from Oversized Post-Blast Exhibits in ANFO Detonations","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe forensic investigation of explosive incidents plays a critical role in event reconstruction, identification of explosive formulations, and judicial proceedings. Ammonium nitrate fuel oil (ANFO) remains one of the most frequently encountered improvised explosives due to its widespread availability, low cost, and high detonation efficiency [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Following detonation, explosive residues are dispersed onto a wide range of substrates, including soil, metals, plastics, and concrete. Oversized and irregular debris presents additional analytical challenges because residue deposition is often uneven, resulting in pronounced surface contamination gradients [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eConventional residue recovery techniques, such as swabbing and solvent rinsing, are routinely applied in forensic casework. However, these methods are primarily optimized for small and relatively uniform exhibits and often yield poor recovery when applied directly to large, heterogeneous post-blast debris [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. To address these limitations, adaptations such as spatially resolved subsampling, improved filtration, and optimized solvent extraction strategies have been proposed (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAnalytical techniques remain central to post-blast residue characterization. Gas chromatography\u0026ndash;mass spectrometry (GC\u0026ndash;MS) provides reliable detection of organic explosive components and fuel oils, while Fourier-transform infrared (FTIR) spectroscopy and classical chemical spot tests are widely used for the identification of inorganic oxidizers and ions [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The effectiveness of these techniques, however, is strongly dependent on the efficiency of the initial sampling and extraction procedures.\u003c/p\u003e \u003cp\u003eWhile recent advances in chemosensors and molecular frameworks have demonstrated high selectivity for nitroaromatic explosives under controlled conditions [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], such approaches are generally unsuitable for complex and contaminated post-blast debris. Comprehensive reviews, including the INTERPOL survey on explosives analysis, highlight the lack of validated workflows for heterogeneous and oversized exhibits and emphasize contamination control as a critical factor in forensic reliability [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The present study addresses this gap by developing and validating an integrated forensic workflow\u0026mdash;combining sequential swabbing, solvent extraction, syringe filtration, and spatial subsampling with complementary analytical techniques\u0026mdash;specifically tailored for oversized ANFO-related post-blast exhibits.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Exhibits Received for Examination\u003c/h2\u003e \u003cp\u003eOversized metallic, plastic, and soil fragments were received for forensic examination from the investigating authority following a post-blast incident involving an ANFO detonation. The exhibits comprised large metal fragments measuring up to 29 inches in length, spades, metallic pots approximately 12 inches in height, a cardboard drum, and a deformed metallic cover (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Control soil samples were collected from unaffected areas in the vicinity of the blast site to serve as negative controls. All exhibits and control samples were packaged individually in clean, sealed containers to prevent cross-contamination during handling and transport [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Residue Recovery and Spatial Subsampling Strategy\u003c/h2\u003e \u003cp\u003eResidues were recovered from oversized post-blast exhibits using a structured residue recovery approach based on sequential swabbing. Cotton applicators were moistened with analytical-grade solvents and applied in a defined sequence\u0026mdash;diethyl ether, acetone, deionized water, sodium hydroxide solution, and pyridine\u0026mdash;to preferentially extract non-polar organic residues followed by polar organic and inorganic components. Swabbing was performed systematically across all accessible surfaces of each exhibit to ensure comprehensive coverage. The collected swabs were extracted into clean glassware, and the combined extracts were filtered through 0.22 \u0026micro;m nylon syringe filters to remove particulate matter and minimize matrix-related interference. The filtrates were subsequently concentrated at room temperature to a final volume of approximately 2\u0026ndash;5 mL prior to instrumental analysis [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOversized post-blast exhibits frequently exhibit highly heterogeneous residue distribution as a result of uneven deposition, secondary fragmentation, and surface-specific adsorption processes. To address this variability, a spatial subsampling strategy was implemented in which large exhibits were systematically divided into discrete surface regions based on geometry, exposure orientation, and visible blast effects. Each region was independently swabbed and extracted rather than combined into a single composite sample, thereby reducing dilution of localized residue hotspots and increasing the probability of recovering trace-level explosive components from contaminated or weathered surfaces (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In addition, spatial subsampling enabled comparative assessment of residue distribution across different areas of the same exhibit, providing valuable contextual information for forensic interpretation. When integrated with sequential swabbing and syringe filtration, this approach significantly enhanced analytical sensitivity, reproducibility, and interpretative reliability for heterogeneous and oversized post-blast debris associated with ANFO detonations.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Analytical Workflow\u003c/h2\u003e \u003cp\u003eA schematic overview of the integrated analytical workflow is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e based on the standard laboratory protocols [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eOrganic residue analysis\u003c/b\u003e: Ether and acetone extracts were examined using thin-layer chromatography (TLC) on silica gel plates, employing chloroform/acetone (1:1, v/v) and toluene/cyclohexane (7:3, v/v) as mobile phases. Visualization was carried out under UV light (254 nm) and by chemical spraying. Confirmatory analysis was performed using GC\u0026ndash;MS for the detection of fuel-oil hydrocarbons and high explosives [\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eInorganic residue analysis\u003c/strong\u003e \u003cp\u003eWater and sodium hydroxide extracts were subjected to classical chemical spot tests for common anions and cations, including nitrate, nitrite, ammonium, and potassium. Selected extracts were further characterized using FTIR spectroscopy.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eFiltration assessment\u003c/strong\u003e \u003cp\u003eThe effect of syringe filtration on analytical clarity and background interference was evaluated by comparing filtered and unfiltered extracts during GC\u0026ndash;MS analysis [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003e2.4. Instrumental Parameters\u003c/b\u003e \u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eGC\u0026ndash;MS\u003c/b\u003e: Analyses were carried out with an electron ionization (EI) source at 70 eV, full-scan mode (m/z 40\u0026ndash;500), on a 30 m \u0026times; 0.25 mm \u0026times; 0.25 \u0026micro;m capillary column. The oven program ramped from 100\u0026deg;C to 280\u0026deg;C with controlled heating rates. Compounds were identified by comparison with NIST library spectra. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e briefs the parameters of the GC-MS method.[\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eTLC\u003c/b\u003e: Developed plates were visualized under UV (254 nm) and by spraying with diphenylamine and sulfuric acid reagents. [\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eFTIR\u003c/b\u003e: ATR-FTIR spectra were recorded from 4000\u0026ndash;400 cm⁻\u0026sup1; at 4 cm⁻\u0026sup1; resolution; spectral matching was performed using instrument libraries. [\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eParameters of the GC-MS Method\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMS transfer line temperature [\u0026deg;C]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIon source temperature [\u0026deg;C]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal Run time [min]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.250\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInlet Temperature [\u0026deg;C]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e230\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCarrier Flow [ml/min]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eGC Oven Temperature Nominal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStart at 100.0\u0026deg;C hold for 0.2 min\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRamp to 220\u0026deg;C at 30\u0026deg;C/min\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHold for 0.3 min at 220\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRamp to 280\u0026deg;C at 80\u0026deg;C/min\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHold for 1 min at 280\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003e\u0026deg;C - degree Celsius, min-minutes\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Quality Control\u003c/h2\u003e \u003cp\u003eProcedural blanks (blank swabs) and negative control samples (control soil) were processed concurrently with questioned exhibits to assess potential environmental and laboratory-derived contamination throughout all stages of the analytical process. Certified reference materials and laboratory standards of commonly encountered explosives and explosive components, including RDX, TNT, PETN, and ANFO constituents, were analyzed under identical instrumental and procedural conditions to support analytical verification and result interpretation. The inclusion of negative controls and reference materials as part of routine quality assurance and quality control measures is consistent with INTERPOL-recommended best practices and ASTM guidance for the forensic examination of explosives and explosive residues, which emphasize contamination monitoring, method validation, and interpretive reliability as essential elements of forensic reporting [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Challenges in the Analysis of Oversized Exhibits\u003c/h2\u003e \u003cp\u003eExtraction from the exhibits of smaller sizes and their debris is possible by rinsing the exhibit with a minimum quantity of solvent in a beaker. In this method, the ingredients of the unexploded and exploded explosives can be easily collected from the exhibits by dissolution. In contrast, oversized exhibits cannot be conveniently immersed or rinsed, making swabbing the primary viable recovery method. Factors such as cotton quality, operator variability, solvent loss, and inefficient transfer of residues from the swab can affect recovery efficiency. Careful and systematic swabbing, combined with filtration and complementary analytical techniques, is therefore essential to minimize analytical uncertainty.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Observations","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1. TLC and GC-MS Examinations\u003c/h2\u003e \u003cp\u003eGC\u0026ndash;MS analysis of ether extracts revealed the presence of high-boiling petroleum hydrocarbons. Hexadecane was identified at a retention time of 14.02 min, with a similarity index (SI) of 792 and a reverse similarity index (RSI) of 929 based on NIST library matching. The corresponding total ion chromatogram (TIC) is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. No high explosives were detected in acetone extracts by TLC or GC\u0026ndash;MS. [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThe mass spectra of the forensic case sample obtained by analysis using the GC-MS method, along with the reference library of mass spectra, are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The x axis presents abundance and y axis presents m/z values.[\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Chemical Examinations\u003c/h2\u003e \u003cp\u003eChemical examination of water, alkaline, and pyridine extracts yielded positive results for nitrate, nitrite, ammonium, potassium, chloride, sulfate, and elemental sulfur in the questioned exhibits. Chlorate, perchlorate, and metallic additives such as aluminium and magnesium were not detected. Observations are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.[\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eObservations of the Chemical Examinations\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSl.No\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChemical Test\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTarget Ion/Analyte\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObservation\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSilver Nitrate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChloride\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGriess Test\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNitrite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGriess reagent\u0026thinsp;+\u0026thinsp;Zn dust\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNitrate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAniline sulphate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChlorate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMethylene blue indicator\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePerchlorate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBarium chloride\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSulphate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZinc Uranyl Acetate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSodium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSodium Cobaltinitrate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePotassium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNessler\u0026rsquo;s reagent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAmmonium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMagneson-I\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMagnesium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSodium Rhodizonate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBarium, Calcium, Strontium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSodium Nitroprusside\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSulphide (NaOH Extract)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAlizarine-S\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMetallic Aluminium (NaOH Extract)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGutzeit\u0026rsquo;s Test\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eArsenic (NaOH Extract)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePyridine\u0026thinsp;+\u0026thinsp;NaOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eElemental Sulphur\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3. FTIR Analysis\u003c/h2\u003e \u003cp\u003eFTIR analysis of aqueous extracts confirmed the presence of nitrate-based oxidizers. Reference spectra of ammonium nitrate and potassium nitrate were used for comparison. Both oxidizers were detected across different extracts, indicating heterogeneous residue distribution on oversized exhibits. Representative spectra are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e.[\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.1. Organic Residue Detection (GC\u0026ndash;MS and TLC)\u003c/h2\u003e \u003cp\u003eGC\u0026ndash;MS analysis of ether extracts confirmed the presence of high-boiling petroleum hydrocarbons, with hexadecane detected at a retention time of 14.02 min (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). This compound is characteristic of diesel oil fractions and supports the presence of fuel oil components consistent with ANFO formulations. The mass spectral profile exhibited a high similarity match with the NIST library, indicating reliable compound identification (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). No high-explosive compounds were detected in acetone extracts by either TLC or GC\u0026ndash;MS analysis, suggesting the absence of secondary high-explosive admixtures within the recovered residues.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.2. Inorganic Residue Detection by Chemical Tests\u003c/h2\u003e \u003cp\u003eChemical spot tests yielded positive responses for nitrite, nitrate, ammonium, chloride, potassium, sulphate ions, and elemental sulphur across multiple post-blast exhibits (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Tests for chlorate, perchlorate, and metallic additives such as aluminium and magnesium were negative. These results are consistent with nitrate-based low explosive residues typically associated with ANFO formulations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.3. FTIR Characterization of Post-Blast Inorganic Oxidizer Residues\u003c/h2\u003e \u003cp\u003eFTIR spectroscopy was employed to characterize inorganic oxidizer residues recovered from oversized post-blast exhibits. Spectra obtained from questioned samples were compared with laboratory reference spectra of ammonium nitrate and potassium nitrate. This variation reflects spatial heterogeneity, with ammonium nitrate detected in some subsamples and potassium nitrate predominating in others\u003c/p\u003e \u003cp\u003eThe ammonium nitrate reference spectrum exhibited a broad N\u0026ndash;H stretching band at approximately 3392 cm⁻\u0026sup1;, along with characteristic absorptions at ~\u0026thinsp;1636 cm⁻\u0026sup1; (ammonium bending) and a strong nitrate asymmetric stretching band at ~\u0026thinsp;1322 cm⁻\u0026sup1;. Additional nitrate-related absorptions were observed at ~\u0026thinsp;1045 cm⁻\u0026sup1; and ~\u0026thinsp;820 cm⁻\u0026sup1;, with lattice vibration bands below 600 cm⁻\u0026sup1;.\u003c/p\u003e \u003cp\u003eIn contrast, the questioned post-blast samples lacked the ammonium N\u0026ndash;H stretching feature near 3400 cm⁻\u0026sup1; and displayed a dominant absorption at ~\u0026thinsp;1364 cm⁻\u0026sup1;, characteristic of nitrate asymmetric stretching in alkali metal nitrates. Additional absorptions at ~\u0026thinsp;953 cm⁻\u0026sup1;, ~\u0026thinsp;823 cm⁻\u0026sup1;, and multiple bands within the 730\u0026ndash;560 cm⁻\u0026sup1; region were consistent with potassium nitrate. The absence of ammonium-specific bands supported exclusion of ammonium nitrate as the primary oxidizer in these subsamples.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e4.4. Workflow Performance in Oversized Exhibits\u003c/h2\u003e \u003cp\u003eSequential swabbing followed by solvent extraction and syringe filtration resulted in improved extract clarity and enhanced analytical performance. Syringe filtration effectively reduced particulate interference and background noise during GC\u0026ndash;MS analysis, as reflected by improved chromatographic resolution (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), facilitating reliable detection of trace-level residues [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Spatially resolved subsampling (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) further contributed to improved recovery from heterogeneous surfaces, minimizing dilution of localized residue hotspots.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Discussion","content":"\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e5.1. Forensic Interpretation of Analytical Findings\u003c/h2\u003e \u003cp\u003eThe combined recovery of petroleum hydrocarbons and nitrate salts confirms the ANFO origin of the post-blast residues and is consistent with molecular fingerprints reported for ANFO detonations in technical reference studies [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The identification of diesel-range hydrocarbons by GC\u0026ndash;MS (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), together with nitrate-based inorganic residues detected by chemical tests (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) and FTIR spectroscopy (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), provides complementary and mutually reinforcing evidence supporting device composition and formulation.\u003c/p\u003e \u003cp\u003eCompared with prior studies employing molecular frameworks and chemosensors for selective detection of nitroaromatic explosives [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], the present workflow directly addresses the analytical challenges posed by large-scale, heterogeneous, and environmentally contaminated post-blast debris. While sensor-based approaches demonstrate high selectivity under controlled laboratory conditions, their applicability to mixed and contaminated post-blast matrices remains limited. In contrast, the integrated methodology described here\u0026mdash;incorporating spatial subsampling (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), sequential solvent swabbing, syringe filtration, and complementary analytical techniques\u0026mdash;provides a robust and adaptable framework for forensic examination of oversized exhibits.\u003c/p\u003e \u003cp\u003eFTIR spectroscopy proved particularly valuable as a rapid screening tool for differentiating between ammonium-based oxidizers and alkali metal nitrates (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), thereby guiding subsequent confirmatory analyses and contextual interpretation. Overall, the workflow enhances analytical sensitivity, improves reproducibility, and strengthens evidentiary reliability, extending forensic capability in the investigation of complex ANFO-related detonation scenarios involving oversized post-blast debris.\u003c/p\u003e \u003c/div\u003e"},{"header":"6. Conclusion","content":"\u003cp\u003eThis study demonstrates that tailored forensic workflows are essential for the reliable analysis of oversized post-blast exhibits. By integrating sequential swabbing, solvent extraction, syringe filtration, and spatial subsampling with complementary analytical techniques, both organic (fuel oil hydrocarbons) and inorganic (nitrate-based) residues were detected with high confidence. Syringe filtration was particularly effective in maximizing recovery and reducing analytical interference, while multi-method corroboration strengthened evidentiary interpretation. These findings confirm the exclusive use of ANFO in the investigated detonation and highlight the broader significance of adapting forensic protocols to heterogeneous, large-scale evidence. Beyond the present case, the validated workflow provides a generalizable framework that enhances evidentiary reliability and strengthens the chemical basis for reconstructing complex detonation events.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eThe following abbreviations are used in this manuscript:\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTLC\u003c/strong\u003e Thin Layer Chromatography\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eGC-MS\u003c/strong\u003e\u0026nbsp; Gas Chromatography Mass Spectrometry\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFTIR\u0026nbsp;\u003c/strong\u003e Fourier Transform Infrared Spectroscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ein.\u003c/strong\u003e inches\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTIC\u003c/strong\u003e Total Ion Chromatogram\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNIST\u003c/strong\u003e National Institute of Standards and Technology\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAR\u003c/strong\u003e Analytical Reagent\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eATR\u0026nbsp;\u003c/strong\u003e Attenuated Total Reflectance\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eANFO\u003c/strong\u003e Ammonium Nitrate Fuel Oil\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePETN\u003c/strong\u003e Penta Erythritol Tetra Nitrate\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTNT\u003c/strong\u003e Tri Nitro Toluene\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRDX\u003c/strong\u003e Research Department Explosive/ Royal Demolition Explosive\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTETRYL\u003c/strong\u003e Trinitrophenylmethylnitramine\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHMX\u003c/strong\u003e High Melting Explosive - Octogen\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eUV\u003c/strong\u003e Ultra Violet\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNaOH\u003c/strong\u003e Sodium Hydroxide\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eAll authors have reviewed, revised, and approved the final manuscript for submission.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eClinical trial number\u003c/h2\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eNone\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization, D.K.; methodology, D.K.; validation, D.K.; formal analysis, D.K.; investigation, D.K.; writing\u0026mdash;original draft preparation, D.K., N.B., S.G.; writing\u0026mdash;review and editing, D.K., N.B., S.G.; visualization, D.K., N.B., S.G.; and supervision, D.K. All the authors have read and agreed to the published version of this manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eI would like to express my gratitude to the Director, Central Forensic Science Laboratory, Pune and Hyderabad, for continuous support and for providing the necessary infrastructure for this study.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe author declares that the data supporting the findings of this study are available within the paper. Should any raw data files be needed in another format, they are available from the author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBraga JWB, Logrado LPL (2024) Evaluation of interferents in sampling materials for analysis of post-explosion residues (explosive emulsion/ANFO) using gas chromatography\u0026ndash;mass spectrometry (GC\u0026ndash;MS). 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Int J Innov Res Technol 11(12). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.64643/IJIRTV12I3-179451-457\u003c/span\u003e\u003cspan address=\"10.64643/IJIRTV12I3-179451-457\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang X, Li C et al (2019) \u003cem\u003eElectron-Rich π-Extended Diindolotriazatruxene-Based Chemosensors with Highly Selective and Rapid Responses to Nitroaromatic Explosives\u003c/em\u003e, \u003cem\u003eChemPlusChem 84\u003c/em\u003e (10), 1623\u0026ndash;1629. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/cplu.201900347\u003c/span\u003e\u003cspan address=\"10.1002/cplu.201900347\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGole B, Bar AK, Mukherjee PS (2014) Modification of Extended Open Frameworks with Fluorescent Tags for Sensing Explosives: Competition between Size Selectivity and Electron Deficiency. 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Journal of Emerging Technologies and Innovative Research (JETIR) October-2025, Volume 12, Issue 10. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.56975/jetir.v12i10.570567\u003c/span\u003e\u003cspan address=\"10.56975/jetir.v12i10.570567\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKumar D (2025) Analytical Techniques for Forensic Investigation of Oversized and Fragmented Exhibits in Mixed Explosive Detonations. This content is a preprint and has not been peer-reviewed, doi:10.26434/chemrxiv-2025-fhfj0\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKumar D, Preprints (2025) 2025090885. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.20944/preprints202509.0885.v1\u003c/span\u003e\u003cspan address=\"10.20944/preprints202509.0885.v1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. This content is a preprint and has not been peer-reviewed\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Post-blast analysis, Oversized exhibits, ANFO, GC–MS, FTIR, Explosive residue analysis","lastPublishedDoi":"10.21203/rs.3.rs-8421591/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8421591/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground:\u003c/h2\u003e \u003cp\u003ePost-blast forensic investigations frequently involve oversized debris such as concrete and metallic fragments, where heterogeneous residue distribution and complex surface matrices complicate explosive residue recovery. Conventional extraction techniques optimized for small and homogeneous samples often prove inadequate for such exhibits, resulting in reduced sensitivity and interpretative uncertainty. This study addresses these challenges by developing and validating an integrated residue recovery workflow specifically tailored for oversized post-blast exhibits associated with ammonium nitrate fuel oil (ANFO) detonations.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eOversized exhibits were examined using a combined approach incorporating sequential solvent swabbing, spatial subsampling, and syringe filtration. Organic residues were analyzed by thin-layer chromatography (TLC) and gas chromatography\u0026ndash;mass spectrometry (GC\u0026ndash;MS), while inorganic residues were characterized using classical chemical spot tests and Fourier-transform infrared (FTIR) spectroscopy. GC\u0026ndash;MS analysis confirmed the presence of high-boiling petroleum hydrocarbons consistent with diesel fuel fractions, and inorganic analyses identified nitrate-based oxidizers, including ammonium and potassium nitrate. Chlorates, perchlorates, and metallic additives were not detected. Spatial subsampling improved trace residue recovery from heterogeneous surfaces, while syringe filtration significantly reduced background interference and enhanced analytical clarity.\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e \u003cp\u003eThe integrated workflow demonstrated reliable and reproducible recovery of both organic and inorganic ANFO residues from oversized post-blast debris. The combined application of spatial subsampling, sequential swabbing, and syringe filtration enhanced analytical sensitivity and forensic interpretability in complex detonation scenarios. This validated approach provides a practical and adaptable framework for forensic laboratories handling large, heterogeneous post-blast exhibits and strengthens the chemical basis for reconstructing ANFO-related explosive events.\u003c/p\u003e","manuscriptTitle":"Forensic Workflow for Residue Recovery from Oversized Post-Blast Exhibits in ANFO Detonations","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-25 05:33:26","doi":"10.21203/rs.3.rs-8421591/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"49580c98-0e79-44db-a6f3-f770893eb414","owner":[],"postedDate":"December 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-25T05:33:28+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-25 05:33:26","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8421591","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8421591","identity":"rs-8421591","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}