Passive Headspace Concentration (PHC)
Definition
ASTM E1412 extraction method. The sealed evidence container is heated at 60-80°C; volatilised hydrocarbons adsorb onto an activated charcoal strip suspended in the headspace. The strip is eluted with CS2 for GC-MS injection. Default method for most fire debris laboratories.
- Primary extraction method
- Default technique used by most fire debris laboratories
- Heating temperature range
- 60-80°C
- Extraction duration
- Typically 16 hours
- Elution solvent
- Carbon disulfide (CS2)
- Analytical instrument
- Gas chromatography-mass spectrometry (GC-MS)
Common questions
What is passive headspace concentration and when is it used?+
PHC is a fire debris extraction method where volatile compounds from evidence are concentrated onto a charcoal strip for analysis. A sealed container holding the evidence is heated to 60-80°C, causing hydrocarbons to vaporize. These vapors adsorb onto an activated charcoal strip suspended above the evidence, concentrating them for later testing. It is the default method used by most fire debris laboratories.
How does the charcoal strip capture volatile compounds?+
The activated charcoal strip suspended in the sealed headspace passively absorbs volatile compounds as they vaporize from the heated evidence. The strip remains in the sealed container for 16 hours during the extraction process. After adsorption, the strip is eluted with carbon disulfide (CS2) to release the concentrated compounds for GC-MS injection and analysis.
What standards govern passive headspace concentration?+
The method is defined by ASTM E1412 and ASTM E2154 standards. These standards specify the heating temperature (60-80°C), the use of sealed containers, the charcoal strip suspension, and the elution procedure. Laboratories follow these standards to ensure consistent evidence analysis.
Related terms
- ASTM E1618
- Standard Test Method for Ignitable Liquid Residues in Extracts from Fire Debris Samples by Gas Chromatography-Mass Spectrometry. The active analytical standard defining...
- ASTM E2154
- Standard Practice for Passive Headspace Concentration with Activated Charcoal. The most widely used extraction method for volatile ILR components from sealed fire...
- ASTM E2998
- Standard Guide for Sampling Improvised Explosive Devices and Post-Blast Debris for Explosive Residue Analysis. Specifies cotton swabs, isopropanol or methanol pre-wetting, swabbing...
- BSA 2023 / IEA Section 45
- The Bharatiya Sakshya Adhiniyam 2023 Section 39 (formerly Indian Evidence Act Section 45) governs expert opinion admissibility in India: opinions of persons...
- Chain of Custody
- The documented chronological record of who collected, handled, transferred, and examined a piece of evidence. For digital evidence, chain of custody includes...
- CrimPR Part 19
- Criminal Procedure Rules Part 19 (England and Wales): the expert-witness procedural code requiring disclosure of qualifications, methodology, limitations, and whether the method...
- Daubert Standard
- The US federal evidentiary standard (Daubert v. Merrell Dow Pharmaceuticals, 1993) requiring that expert testimony be based on scientifically valid methods with...
- DB-5 Column
- A gas chromatography capillary column with a 5% phenyl-95% dimethylpolysiloxane stationary phase, the standard column for fire debris GC-MS analysis. Provides adequate...
- Extracted Ion Profile (EIP)
- A GC-MS chromatographic display plotting only ions of a specified m/z value against retention time, effectively filtering out all compounds that do...
- Friction Lid
- The press-on metal lid used to seal evidence cans for fire debris. Seated by pressing firmly around the rim; allows field packaging...
- Frye Standard
- The US legal test for admissibility of scientific evidence, originating from Frye v. United States (1923), which required that a technique be...
- Ignitable Liquid
- In fire debris analysis, any flammable liquid that could serve as an accelerant. E1618 classifies ignitable liquids into eight categories based on...
Explained in these topics
- Fire Debris Analysis: GC-MS and ASTM E1618 Pattern RecognitionASTM E1412 extraction method. The sealed evidence container is heated at 60-80°C; volatilised hydrocarbons adsorb onto an activated charcoal strip suspended in...
- Lab Equipment, Evidence Handling and Chain of CustodyThe ASTM E2154 extraction method in which a sealed, heated evidence can drives ILR volatiles into the headspace where they are adsorbed onto a suspended activa...
- Standards, Accreditation and Admissibility in Fire and ExplosivesThe ASTM E2154 extraction technique in which a charcoal strip suspended in a sealed, heated evidence can adsorbs volatile ILR components from the headspace ove...