Total Ion Chromatogram (TIC)
Definition
A GC-MS chromatographic output plotting the summed intensity of all detected ions at each retention time. Provides the full-pattern overview of a fire debris extract and is the primary display for ASTM E1618 pattern recognition.
- Plots
- Summed intensity of all ions vs retention time
- Source
- GC-MS output
- Governing standard
- ASTM E1618 pattern recognition
- Use
- Full-pattern overview of a fire debris extract
Common questions
Why is the TIC used for pattern recognition rather than single-ion analysis in fire debris cases?+
Ignitable liquids produce a characteristic overall peak pattern across many compounds, and comparing that whole pattern to reference ignitable-liquid classes under ASTM E1618 is more reliable than relying on any single compound, which pyrolysis products from the burned materials themselves can also produce.
Can pyrolysis products from burned building materials be mistaken for an ignitable liquid on the TIC?+
Yes, background pyrolysis from carpet, flooring, or furnishings can generate compounds that overlap with ignitable liquid components, which is why analysts examine the full TIC pattern and extracted ion profiles rather than flagging isolated peaks as proof of an accelerant.
How does the TIC differ from an extracted ion chromatogram in the same analysis?+
The TIC sums all ion signals at each retention time for a broad overview, while an extracted ion chromatogram isolates specific mass fragments characteristic of a target compound class, giving a cleaner, more selective view used to confirm what the TIC pattern suggests.
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...
- Carbon Disulfide (CS2)
- The standard elution solvent for activated charcoal strips in ASTM E1412 passive headspace analysis. Selected for its low UV absorption, minimal GC-FID...
- Evaporative Weathering
- The preferential loss of volatile components (benzene, toluene, C5-C7 alkanes) from an ignitable liquid residue during and after a fire, altering the...
- 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 Reference Collection (ILRC)
- A database of GC-MS chromatographic data for over 1,100 ignitable liquid products maintained by the National Centre for Forensic Science at the...
- Light Petroleum Distillate (LPD)
- The ASTM E1618 ignitable liquid class covering C4-C9 aliphatic products (charcoal lighter fluid, camping fuel, some paint thinners). The class most frequently...
- Passive Headspace Concentration
- The ASTM E1412 method in which an activated charcoal strip is suspended in a sealed container above heated fire debris (60-80°C, 16...
- Tropylium Cation (M/z 91)
- The C7H7+ fragment ion produced by rearrangement of alkylbenzenes in the EI ion source of a mass spectrometer. The diagnostic ion for...
- Unresolved Complex Mixture (UCM)
- The broad hump of hundreds of co-eluting cycloalkane and isoalkane compounds in the TIC of heavy petroleum products (diesel, heavy fuel oil,...