Application of Comprehensive Two-Dimensional Gas Chromatography - Mass Spectrometry to Forensic Science Investigations Glenn S. Frysinger Richard B.
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1 Application of Comprehensive Two-Dimensional Gas Chromatography - Mass Spectrometry to Forensic Science InvestigationsGlenn S. FrysingerRichard B. GainesDepartment of ScienceU.S. Coast Guard AcademyNew London, Connecticut
2 U.S. Coast Guard AcademyU.S. Military Academy located in New London, Connecticut on the Thames River near Long Island SoundCadets earn a B.S. degree in science, engineering, government, or management.The academic degree program & professional training prepares graduates to receive commissions in the U.S. Coast GuardFive year service commitment
3 Application of GC × GC/MS to Forensic Science Investigations Oil Spill FingerprintingFire Debris Analysis
4 Application of GC × GC/MS to Forensic Science Investigations GC × GC and GC × GC/MS methods are in competition with GC/MS standard methods (ASTM, EPA).
5 Oil Spill Fingerprinting – ASTM D5739 Use GC/MS to compare the chemical composition of petroleum oil spills with suspected sources.Use GC/MS to identify and compare specific classes of compounds that are both unique descriptors of oil and resistant to environmental degradation.Chemical analysis supports a conclusion of similar, dissimilar, or inconclusive.
9 Spill Source A Source B GC × GC – FID, Rotating Thermal Modulator Carbon number1314151617181920Gaines et al., Environ. Sci. & Technol. 33 (1999)
10 C2N C3N C4N Spill Source A Source B GC × GC – FID, Rotating Thermal ModulatorSpillC2NC3NC4NSource ASource BCarbon number1314151617181920Gaines et al., Environ. Sci. & Technol. 33 (1999)
11 ObservationsThe patterns in GC × GC images are equal to multiple GC/MS extracted ion chromatograms.Visual analysis of GC × GC images enables rapid identification of similarities and differences between samples.Integration of GC × GC images permits quantitative description of similarities and differences between samples.
12 Fire Debris Analysis – ASTM E1618 Use GC/MS to identify ignitable liquids (single compounds, or petroleum-based formulations or distillate products).Use GC/MS to identify the residue of ignitable liquids in fire debris samples.GC/MS is the preferred method over GC if samples contain high background levels of substrate materials or fire-produced combustion and pyrolysis products.
13 Fire Debris is a Complex Chemical Mixture Substrate materialPyrolysis productsCombustion productsIgnitable liquid ?
19 105GC/MS12091Analysis of the EIC shows the presence of compounds characteristic of specific ignitable liquidsExperiment10512091Librarym/z 120C3-Benzenes152025NIJ0022, NIJ0023
20 77105GC/MS120Analysis of the EIC shows the presence of compounds NOT characteristic of specific ignitable liquidsExperiment105O77120Librarym/z 120C3-Benzenes152025NIJ0022, NIJ0023
21 GC/MS51118?77103Analysis of the EIC shows mixtures of compounds that are unidentifiable by MS.6391115121Experimentm/z 120C3-Benzenes152025NIJ0022, NIJ0023
22 Problems with ASTM E1618The idea that “major ions are characteristic of each compound type” is false. Truly unique ions do not exist for any target class.Matrix compounds unrelated to target compounds for a suspected ignitable liquid can contribute to the EIC. The EIC will contain extra peaks that may or may not coelute with the target compounds.Matrix compounds are sometimes exactly the same as the target compounds from a suspected ignitable liquid.Mass selectivity is an insufficient second dimension.
23 GC × GC/MS TIC of Fire Debris 4.03.0Time (s)2.01.00.0510152025303540Time (min)NIJ0006
28 Gasoline – Target Compound Analysis 1,3,5-trimethylbenzene1,2,4-trimethylbenzene1,2,3-trimethylbenzeneindan2-methylindan1-methylindan1,2,4,5-tetramethylbenzene1,2,3,5-tetramethylbenzene5-methylindan4-methylindantetrahydronaphthalene2-methylnaphthalene1-methylnaphthalene2-ethylnaphthalene1-ethylnaphthalene1,3-dimethylnaphthalene2,3-dimethylnaphthaleneC3BenzenesTarget compounds are often identified based on 1D retention and ratios of molecular or fragment ions.C4BenzenesC1NaphthalenesC2Naphthalenes
29 GCImage screen capture GC × GC of Fire DebrisISNIJ0221
54 ObservationsGC × GC/MS offers solutions to problems inherent in the GC/MS analysis of complex fire debris samples.Target compounds can be selected and identified in GC × GC/MS data with MS-based algorithms.“Target Compound Chromatograms”Target compounds can be selected and identified with templates matched by two-dimensional retention time position, and MS algorithm or MS probability.
55 What’s Next Chemometric data analysis. Chemometric analysis with peak tables produced from GC × GC chromatograms.Chemometric analysis with GC × GC images.LCDR Greg Hall, April 3, 2007Image alignmentImage normalizationPCA, PLS DA, PARAFAC
56 Acknowledgements National Institute of Justice U.S. Coast Guard AcademyLecoGC ImageThis project was supported by Grant Number (2002-RB-052) awarded by the National Institute of Justice, Office of Justice Programs, US Department of Justice. Points of view in this document are those of the author and do not necessarily represent the official position or policies of the US Department of Justice.