Application of Comprehensive Two-Dimensional Gas Chromatography - Mass Spectrometry to Forensic Science Investigations Glenn S. Frysinger Richard B. Gaines Department of Science U.S. Coast Guard Academy New London, Connecticut glenn.s.frysinger@uscg.mil

U.S. Coast Guard Academy U.S. Military Academy located in New London, Connecticut on the Thames River near Long Island Sound Cadets 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 Guard Five year service commitment

Application of GC × GC/MS to Forensic Science Investigations Oil Spill Fingerprinting Fire Debris Analysis

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).

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.

Oil Spill Fingerprinting – ASTM D5739

Oil Spill Fingerprinting Coast Guard Marine Safety Laboratory Case Marine diesel fuel spill. Fuel from two suspect fishing vessels in the area sampled as potential sources. Oil Spill Fingerprinting GC/MS TIC Spill (min) 5 10 15 20 25 30 35 Source A (min) 5 10 15 20 25 30 35 Source B (min) 5 10 15 20 25 30 35 Gaines et al., Environ. Sci. & Technol. 33 (1999) 2106-2112.

Oil Spill Fingerprinting GC/MS m/z 156 C2-Naphthalenes GC/MS m/z 170 C3-Naphthalenes Spill Source A Source B

Spill Source A Source B GC × GC – FID, Rotating Thermal Modulator Carbon number 13 14 15 16 17 18 19 20 Gaines et al., Environ. Sci. & Technol. 33 (1999) 2106-2112.

C2N C3N C4N Spill Source A Source B GC × GC – FID, Rotating Thermal Modulator Spill C2N C3N C4N Source A Source B Carbon number 13 14 15 16 17 18 19 20 Gaines et al., Environ. Sci. & Technol. 33 (1999) 2106-2112.

Observations The 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.

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.

Fire Debris is a Complex Chemical Mixture Substrate material Pyrolysis products Combustion products Ignitable liquid ?

Fire Debris Analysis – ASTM E1618

GC/MS Are these the same ? ASTM E 1618 75% Weathered Gasoline Reference chromatogram TIC 5 10 15 20 25 30 35 40 45 Time (min) Are these the same ? Fire Debris TIC ASTM E 1618 NIJ0022

Fire Debris Analysis – ASTM E1618

GC/MS m/z 106 C2-Benzenes m/z 120 C3-Benzenes m/z 134 C4-Benzenes Fire Debris EICs 5 10 15 20 25 30 35 40 45 Time (min) Fire Debris TIC ASTM E 1618 NIJ0022

GC/MS m/z 106 m/z 120 m/z 134 Gasoline Gasoline Debris Debris Gasoline C2-Benzenes Gasoline m/z 120 C3-Benzenes Gasoline Debris 12 15 Debris m/z 134 C4-Benzenes 15 20 25 Gasoline Debris ASTM E 1618 20 25 30 NIJ0022, NIJ0023

105 GC/MS 120 91 Analysis of the EIC shows the presence of compounds characteristic of specific ignitable liquids Experiment 105 120 91 Library m/z 120 C3-Benzenes 15 20 25 NIJ0022, NIJ0023

77 105 GC/MS 120 Analysis of the EIC shows the presence of compounds NOT characteristic of specific ignitable liquids Experiment 105 O 77 120 Library m/z 120 C3-Benzenes 15 20 25 NIJ0022, NIJ0023

GC/MS 51 118 ? 77 103 Analysis of the EIC shows mixtures of compounds that are unidentifiable by MS. 63 91 115 121 Experiment m/z 120 C3-Benzenes 15 20 25 NIJ0022, NIJ0023

Problems with ASTM E1618 The 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.

GC × GC/MS TIC of Fire Debris 4.0 3.0 Time (s) 2.0 1.0 0.0 5 10 15 20 25 30 35 40 Time (min) NIJ0006

GC/MS m/z 120 C3-Benzenes Experiment 15 20 25 51 118 77 103 91 63 115 121 Experiment m/z 120 C3-Benzenes 15 20 25 NIJ0022, NIJ0023

GC × GC/MS TIC of Fire Debris 4.0 3.0 Time (s) 2.0 1.0 0.0 5 10 15 20 25 30 35 40 Time (min) NIJ0006

121 N 106 79 GC × GC/MS TIC 4.0 118 103 91 78 63 51 3.0 120 105 77 91 Time (s) 2.0 43 O 58 69 85 142 1.0 41 57 71 112 142 0.0 20

Fire Debris Analysis – ASTM E1618

Gasoline – Target Compound Analysis 1,3,5-trimethylbenzene 1,2,4-trimethylbenzene 1,2,3-trimethylbenzene indan 2-methylindan 1-methylindan 1,2,4,5-tetramethylbenzene 1,2,3,5-tetramethylbenzene 5-methylindan 4-methylindan tetrahydronaphthalene 2-methylnaphthalene 1-methylnaphthalene 2-ethylnaphthalene 1-ethylnaphthalene 1,3-dimethylnaphthalene 2,3-dimethylnaphthalene C3Benzenes Target compounds are often identified based on 1D retention and ratios of molecular or fragment ions. C4Benzenes C1Naphthalenes C2Naphthalenes

GCImage screen capture GC × GC of Fire Debris IS NIJ0221

GC × GC/MS Mass Spectra 1,3,5 - trimethylbenzene 100 105 80 60 40 120 77 91 20 1,3,5 - trimethylbenzene 100 105 80 60 40 120 77 91 20 1,2,4 - trimethylbenzene 100 105 80 60 40 120 77 91 20 1,2,3 - trimethylbenzene

GC × GC/MS m/z 120 Extracted GCImage screen capture GC × GC/MS m/z 120 Extracted m/z 120 is the molecular ion for the C3 benzene isomers

C3B Target Compound GC × GC/MS GCImage screen capture C3B Target Compound GC × GC/MS Extract the total ion signal at all places where m/z 105 is the base peak in the mass spectrum

C3B Target Compound GC × GC/MS GCImage screen capture C3B Target Compound GC × GC/MS Add the condition that m/z 120 abundance must be > 20% of the base peak

C3B Target Compound GC × GC/MS GCImage screen capture C3B Target Compound GC × GC/MS Add the condition that m/z 91 must be less than 20% of the base peak

C3B Target Compound GC × GC/MS GCImage screen capture C3B Target Compound GC × GC/MS

GC × GC/MS Mass Spectra 2- methylindan Peak Selection Rules 100 80 60 40 20 132 117 115 91 77 2- methylindan Peak Selection Rules 117 = base peak 115 = 2nd most abundant 132 > 10% abundant 100 80 60 40 20 132 117 115 91 77 1- methylindan 100 80 60 40 20 132 117 115 91 77 5- methylindan 100 80 60 40 20 132 117 115 91 77 4- methylindan

GC × GC/MS m/z 132 Extracted GCImage screen capture GC × GC/MS m/z 132 Extracted m/z 132 is the molecular ion for the methylindan isomers

GC × GC/MS m/z 117 Extracted GCImage screen capture GC × GC/MS m/z 117 Extracted m/z 117 is the base peak for the methylindan isomers

Methyindan Target Compound GC × GC/MS GCImage screen capture Methyindan Target Compound GC × GC/MS unknown peak

GC × GC/MS Mass Spectra Peak Selection Rules 117 = base peak 115 = 2nd most abundant 132 > 10% abundant 100 80 60 40 20 132 117 115 91 77 dimethylstyrene (tentative identification)

GC × GC/MS Mass Spectra Peak Selection Rules 117 = base peak 115 = 2nd most abundant 132 > 10% abundant 100 80 60 40 20 132 117 115 91 77 dimethylstyrene (tentative identification) New Peak Selection Rules 117 = base peak 115 = 2nd most abundant 115 < 60% abundant 132 > 10% abundant 100 80 60 40 20 132 117 115 91 77 2- methylindan

Methyindan Target Compound GC × GC/MS GCImage screen capture Methyindan Target Compound GC × GC/MS

Gasoline – Target Compound Analysis 1,3,5-trimethylbenzene 1,2,4-trimethylbenzene 1,2,3-trimethylbenzene indan 2-methylindan 1-methylindan 1,2,4,5-tetramethylbenzene 1,2,3,5-tetramethylbenzene 5-methylindan 4-methylindan tetrahydronaphthalene 2-methylnaphthalene 1-methylnaphthalene 2-ethylnaphthalene 1-ethylnaphthalene 1,3-dimethylnaphthalene 2,3-dimethylnaphthalene C3Benzenes C4Benzenes C1Naphthalenes C2Naphthalenes

GC × GC/MS Total Ion Chromatogram GCImage screen capture GC × GC/MS Total Ion Chromatogram IS ASTM Standard Compounds NIJ0201 10 µg ASTM standard mix

GC × GC/MS Total Ion Chromatogram GCImage screen capture GC × GC/MS Total Ion Chromatogram 1 ng each compound on column IS ASTM Standard Compounds NIJ0201 10 µg ASTM standard mix

GC × GC/MS Total Ion Chromatogram GCImage screen capture GC × GC/MS Total Ion Chromatogram IS 75% Weathered Gasoline NIJ0220 100 µg 75% Wx gasoline

GC × GC/MS Template Results GCImage screen capture GC × GC/MS Template Results 75% Weathered Gasoline

GC × GC/MS Total Ion Chromatogram GCImage screen capture GC × GC/MS Total Ion Chromatogram Fire Debris NIJ0221 100 µg 75% Wx gasoline / nylon carpet matrix

GC × GC/MS Total Ion Chromatogram GCImage screen capture GC × GC/MS Total Ion Chromatogram Nylon Matrix NIJ0217 nylon carpet matrix

Fire Debris = Gasoline + Matrix 1-methylnaphthalene Matrix 2-methylnaphthalene Fire Debris = Gasoline + Matrix IS Gasoline dodecane tetrahydronaphthalene 4-methylindan 5-methylindan 1,2,3,5-tetramethylbenzene 1,2,4,5-tetramethylbenzene 1-methylindan 2-methyindan indan 1,2,3-trimethylbenzene 1,2,4-trimethylbenzene 1,3,5-trimethylbenzene Peak Volume

GC × GC/MS Total Ion Chromatogram GCImage screen capture GC × GC/MS Total Ion Chromatogram 56 Peak Aromatics Template 75% Weathered Gasoline NIJ0220 100 µg 75% Wx gasoline

GC × GC/MS Total Ion Chromatogram GCImage screen capture GC × GC/MS Total Ion Chromatogram 56 Peak Aromatics Template (46 of 56 matched) Fire Debris NIJ0221 100 µg 75% Wx gasoline / nylon carpet matrix

GC × GC/MS Peak Deconvolution GCImage screen capture GC × GC/MS Peak Deconvolution NIJ0221 100 µg 75% Wx gasoline / nylon carpet matrix

Observations GC × 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.

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, 2007 Image alignment Image normalization PCA, PLS DA, PARAFAC

Acknowledgements National Institute of Justice U.S. Coast Guard Academy Leco GC Image This 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.