Py-GC-MS
Definition
Pyrolysis gas chromatography mass spectrometry. Thermal decomposition of a paint sample, separation of fragments, mass spectral identification. Definitive identification of polymer binders.
- Temperature range
- 600-700 degrees Celsius (thermal decomposition)
- Sample size
- 50-100 microgrammes
- Primary use
- Definitive identification of polymer binders in paint evidence
- Standard
- ASTM E2937
Common questions
What does Py-GC-MS do with paint samples?+
Py-GC-MS thermally decomposes a paint sample (50-100 microgrammes at 600-700 degrees Celsius), breaks it into smaller chemical fragments, and then identifies those fragments using gas chromatography and mass spectrometry. This allows forensic analysts to definitively identify the polymer binders in the paint, which is useful for matching paint evidence.
How much paint is needed for Py-GC-MS analysis?+
Only 50-100 microgrammes of paint are required. This small sample size makes the technique practical for forensic work where evidence is often limited and sampling must be minimally destructive.
Is Py-GC-MS a standard forensic method?+
Yes. Py-GC-MS procedures are standardized under ASTM E2937, ensuring consistent and defensible results across laboratories.
Related terms
- ASTM E2937
- ASTM International standard guide for identification of paint binders by pyrolysis-GC-MS; specifies pyrolysis conditions, GC column, oven program, and diagnostic ion reporting.
- ATR (Attenuated Total Reflectance)
- An FTIR sampling mode in which the sample is pressed against a diamond or ZnSe crystal and the evanescent wave probes the...
- Backscattered Electron (BSE) Imaging
- An SEM imaging mode sensitive to atomic number and crystallographic texture; can reveal grain-boundary elongation patterns in the sub-surface cold-worked zone after...
- Binder
- The polymer matrix that holds pigments in place and bonds the paint to the substrate. Identifies paint type (alkyd, acrylic, polyurethane, epoxy)...
- E-Coat
- Electrocoat primer, the first layer applied to a clean steel/aluminium substrate via cathodic electrodeposition. Usually black, epoxy-based, near-universal on modern automotive bodies.
- ENFSI EPG Protocol
- European Network of Forensic Science Institutes Expert Working Group on Paint protocol; the European standard for paint comparison examination sequence and reporting.
- FTIR Microspectroscopy
- Fourier-transform infrared spectroscopy collected from a microscope-focused spot of 10-20 µm diameter; the primary technique for paint binder characterisation.
- IRUG Database
- Infrared and Raman Users Group spectral database; covers historic pigments, artists' materials, and museum-object coatings. Primary reference for art-investigation paint analysis.
- Likelihood Ratio Reporting
- A Bayesian framework for reporting paint-comparison conclusions, expressing the probability of the observed data given the hypothesis of common source versus the...
- Microtome Cross-Section
- A thin section of a paint chip cut perpendicular to the layer planes, allowing each layer to be examined separately by microscopy...
- PDQ
- Paint Data Query database (RCMP-maintained). Cross-referenced from glass work when a vehicle is identified through paired glass and paint evidence.
- Pigment
- Insoluble particles that give colour and opacity. Titanium dioxide (white), iron oxides (red/brown), carbon black (black), organic colorants (blues, reds). SEM-EDX reports...
Explained in these topics
- Paint Evidence: Layers, Coating Structure and Instrumental AnalysisPyrolysis gas chromatography mass spectrometry. Thermal decomposition of a paint sample, separation of fragments, mass spectral identification. Definitive iden...
- Paint Layer Examination: Cross-Section, FTIR and Py-GC-MSPyrolysis gas chromatography-mass spectrometry; thermally decomposes 50-100 µg of paint polymer at 600-700 C, then identifies the volatile fragments by GC-MS....