SPME
Definition
Solid-phase microextraction. A polymer-coated fused-silica fibre (typically PDMS or PDMS-DVB) is exposed to vial headspace, then thermally desorbed in the GC injector. Faster than charcoal strip, lower capacity.
- Fibre coating
- Typically PDMS or PDMS-DVB (polydimethylsiloxane or a copolymer with divinylbenzene)
- Substrate
- Fused-silica fibre coated with the polymer
- Sample preparation
- No solvent needed; analytes adsorb directly from headspace or sample contact
Common questions
What does SPME stand for and how does it work in forensics?+
SPME stands for solid-phase microextraction. A thin fibre coated with a polymer like PDMS (polydimethylsiloxane) is exposed to a sample or its headspace, where analytes stick to the coating. The fibre is then inserted into a gas chromatograph injector where heat causes the trapped compounds to desorb and enter the instrument for analysis.
Why use SPME instead of other extraction methods?+
SPME is faster than traditional charcoal strips and requires no solvent, making it efficient for volatile compounds. It is ideal for headspace analysis in accelerant detection and poison extraction because it concentrates analytes directly onto the fibre without liquid sample preparation.
What are the limitations of SPME?+
SPME has lower sample capacity than some other extraction techniques, meaning it may not handle very large volumes or high concentrations as effectively. It is faster than charcoal strips but this lower capacity is the key trade-off to weigh when choosing an extraction method.
Related terms
- ASE
- Accelerated solvent extraction (Dionex ASE). Pressurised solvent at elevated temperature pushes the analyte off the tissue matrix in minutes, replacing overnight Soxhlet.
- ASTM E1387 / E1618
- ASTM standards for ignitable-liquid residue analysis. E1387 was the older colour-coded scheme; E1618 (current) defines the modern eight-class system based on GC-MS...
- Conway Microdiffusion Cell
- A two-compartment glass or ceramic dish with a central well and an outer ring, sealed at the rim. The poison is released...
- 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...
- Ignitable Liquid
- In fire debris analysis, any flammable liquid that could serve as an accelerant. E1618 classifies ignitable liquids into eight categories based on...
- Passive Headspace Charcoal-Strip Extraction
- ASTM E1412 method. Fire debris is sealed in an unlined metal can with a suspended activated-charcoal strip, heated to 60 to 80...
- Petroleum Fractions
- Crude-oil distillation cuts ordered by boiling range: light (C4 to C9, pentane, hexane, naphtha), medium (C8 to C12, mineral spirits, kerosene), heavy...
- Pyrolysis Products
- Hydrocarbons released when synthetic substrates (polyurethane foam, carpet, vinyl flooring) burn or smoulder. They overlap the petroleum range and are the main...
- QuEChERS
- Quick, Easy, Cheap, Effective, Rugged and Safe sample-prep protocol for pesticide residues. Acetonitrile extraction, MgSO4 + NaCl partition, dispersive SPE clean-up with...
- SLE
- Supported liquid extraction. Diatomaceous earth columns absorb the aqueous sample as a thin film and a single pass of organic solvent elutes...
- SPE
- Solid-phase extraction. Sample is loaded onto a packed sorbent cartridge (C18, mixed-mode MCX/MAX, polymeric Oasis HLB), washed and selectively eluted. The dominant...
- Stas-Otto Procedure
- Classical 1851/1856 acid-base liquid-liquid fractionation. Acidify with tartaric acid and extract acidic and neutral organics into ether, then alkalise and extract bases...
Explained in these topics
- Analysis of Petroleum Products and Fire AccelerantsSolid-phase microextraction. A polymer-coated fused-silica fibre (typically PDMS or PDMS-DVB) is exposed to vial headspace, then thermally desorbed in the GC i...
- Extraction, Isolation and Clean-up of Poisons from VisceraSolid-phase microextraction. A polymer-coated fibre is exposed to headspace or sample, analytes adsorb, the fibre is then thermally desorbed in a GC injector....