Forensic Chemistry: ILR Extraction (SPME, Charcoal Strip, ASTM Standards)
Published:
Questions
29
Duration
30 min
Faculty-reviewed
0
Updated
24 May 2026
About this mock
This mock drill covers the laboratory methods used to separate and identify ignitable liquid residues (ILR) from fire debris, a core topic in UGC-NET Forensic Science Paper II Unit VI. The four ASTM-recognised extraction techniques are examined in depth: passive headspace concentration with activated charcoal strip (ASTM E1412-19), passive headspace SPME with a PDMS 100-micrometre fibre (ASTM E2154-15), dynamic headspace purge-and-trap on a Tenax sorbent (ASTM E1413-19), and direct solvent extraction with pentane or hexane. Each method is tested at the operational detail level that routinely appears in examinations: incubation temperature and time, desorption solvent identity (CS2 for ACS), thermal desorption conditions for SPME, sorbent type for dynamic headspace, and the sensitivity trade-off that makes ACS the preferred choice for trace residues. GC-MS identification under ASTM E1618-19 is tested separately from the extraction step, as the ASTM E30 committee structures them, including the nine ignitable liquid classes and the substrate blank comparison requirement.
This mock is designed for UGC-NET Paper II aspirants, NFSU MSc and MSc Forensic Chemistry students, CFSL and state FSL trainees, and candidates preparing for FACT and GCFA-equivalent practical knowledge assessments. Sample-container selection (new metal paint cans versus polyethylene bags versus glass jars with metal lids), cross-contamination prevention protocols, and the handling of compromised-seal evidence under BNSS Section 176 are tested in scenario form. Substrate interference from burned carpet (SBR latex producing styrene and alkylnaphthalenes), polyurethane foam (TDI pyrolysis series), and pine wood (lignin-derived guaiacols and cellulose-derived furfurals) are tested in the interpretation section, mirroring real CFSL casework decisions.
Topics covered:
- Activated charcoal strip method: 16 h at 60 degrees Celsius, CS2 desorption, ASTM E1412-19
- SPME PDMS 100-micrometre fibre: 15-30 min equilibration, thermal GC desorption, ASTM E2154-15
- Dynamic headspace purge-and-trap: Tenax sorbent, thermal desorption, ASTM E1413-19
- Direct solvent extraction: pentane/hexane, matrix co-extraction limitation
- ASTM E1618-19: nine ILR classes, substrate blank comparison, reference standards
- Fire-debris container selection: metal cans vs polyethylene permeability
- Cross-contamination prevention: glove and tool discipline at each collection point
- Substrate pyrolysis interferences: carpet, polyurethane foam, pine wood
- CFSL workflow: BNSS Section 176, reference standard comparison, report conclusions
Allow 30 minutes.
Sources & references
Questions in this mock are written and verified against the following sources. Citations are recorded per question and shown in the explanation after submission.
- cited in 9 questions
Stauffer E, Dolan J A, Newman R -- Fire Debris Analysis, Academic Press, 2008
Chapter 9, Passive headspace concentration with activated charcoal strip: CS2 desorption and GC-MS analysis
- cited in 5 questions
DeHaan J D, Icove D J -- Kirk's Fire Investigation, 7th Edition, Pearson Prentice Hall, 2012
Chapter 13, Direct solvent extraction: pentane wash, matrix co-extraction problem and comparison with headspace methods
- cited in 5 questions
ASTM International -- ASTM E1618-19, Standard Test Method for Ignitable Liquid Residues in Extracts from Fire Debris Samples by Gas Chromatography-Mass Spectrometry
Section 10, Interpretation: comparison of fire-debris extract against substrate background and reference standards
- cited in 3 questions
Pawliszyn J -- Handbook of Solid Phase Microextraction, Elsevier, 2012
Chapter 4, Thermal desorption of SPME fibres in the GC injector: temperature, time and carryover management
- cited in 2 questions
ASTM International -- ASTM E2154-15, Standard Practice for Separation of Ignitable Liquid Residues from Fire Debris Samples by Passive Headspace Concentration With Solid Phase Microextraction
Section 8, Procedure: PDMS fibre exposure time of 15 to 30 minutes at 60 degrees Celsius for headspace equilibration
- cited in 2 questions
ASTM International -- ASTM E1413-19, Standard Practice for Separation of Ignitable Liquid Residues from Fire Debris Samples by Dynamic Headspace Concentration
Section 6, Materials: Tenax TA or Tenax GR sorbent tube specification and thermal desorption procedure
- cited in 2 questions
ASTM International -- ASTM E1412-19, Standard Practice for Separation of Ignitable Liquid Residues from Fire Debris Samples by Passive Headspace Concentration With Activated Charcoal
Section 8, Procedure: incubation temperature 60 degrees Celsius, minimum 16 hours, charcoal strip suspended in headspace
- cited in 1 question
Bharatiya Nagarik Suraksha Sanhita (BNSS) 2023, Ministry of Law and Justice, Government of India
Section 176: Inquiry into the cause of death, fire, or explosion and collection of forensic exhibits; replaces CrPC 1973 Section 174
Open source
How our mocks are built
Questions are written and edited by the ForensicSpot team and cited from peer-reviewed forensic textbooks, official syllabi and primary case law. Each one is verified before publishing. Detailed explanations show after you submit, so the test stays a real test. See a mistake? Tell us.
Common questions
What does the Forensic Chemistry: ILR Extraction (SPME, Charcoal Strip, ASTM Standards) mock cover?+
This mock drill covers the laboratory methods used to separate and identify ignitable liquid residues (ILR) from fire debris, a core topic in UGC-NET Forensic Science Paper II Unit VI. The four ASTM-recognised extraction techniques are examined in depth: passive headspace concentration with activated charcoal strip (ASTM E1412-19), passive headspace SPME with a PDMS 100-micrometre fibre (ASTM E2154-15), dynamic headspace purge-and-trap on a Tenax sorbent (ASTM E1413-19), and direct solvent extra
How many questions and how long is the test?+
29 multiple-choice questions, 30 minutes total. Difficulty: medium. Tier: Premium.
Who is this mock for?+
Forensic science students and aspirants who want timed, exam-style practice with explanations and verified source citations on Forensic Chemistry, NET. Useful for postgraduate entrance preparation and for BSc / MSc forensic students testing their recall under time.
Are the questions reviewed?+
Each question carries a verified source citation. Faculty review for individual questions is in progress.
Do I need an account to take this mock?+
Yes, a free ForensicSpot account is required to start a timed attempt — this lets you save progress, see per-question explanations after submission, and track your topic-level performance over time.