 Analysis of Gunshot Residue By X- Ray Fluorescence, Raman Spectroscopy, and Inductively Coupled Plasma Delaney Caudill Courtney Belanger

Background  Gunshot Residue (GSR) is a type of physical trace evidence that is released when a gun is fired  Analysis of GSR is an important technique in forensic science  It may place an individual at the scene of the crime  GSR is composed of inorganic and organic components

Significance and Purpose  To allow for nondestructive forensic analysis and detection  To detect GSR components using XRF and Raman  To quantify concentrations of GSR analytes using the ICP

Samples and Analytes InorganicOrganic IronEthyl Centralite Copper2-Nitrodiphenylamine Lead Barium Zinc Samples CaliberDistance.22< 3 feet.38< 3 feet.45< 3 feet Shotgun: 12 gauge4-5 feet

Method: XRF  Spiked sample was created  Solid reference and unknown samples were directly placed on XRF

Method: XRF  Soaked reference and unknown sample in 10 mL of 0.1 M nitric acid  Soaked for 48 hr  Pipetted 1 mL of solution into liquid sample holder for XRF

Method: Raman Samples Methyl ethyl Ketone (MEK solvent) Solid Ethyl Centralite Standard Solid 2-Nitrodiphenylamine Standard 100 mg of ethyl centralite in 0.5 mL of MEK 100 mg of 2-Nitrodiphenylamine in 0.5 mL of MEK.22 Caliber.38 Caliber.45 Caliber Shotgun: 12 gauge Soaked four unknown samples for 1.5 weeks in 10 mL of MEK

Method: ICP  Standards were created: 5, 10, 20, 30, 40 ppm  Unknown samples soaked for 2 weeks before analysis by ICP  Standards and unknown samples were run on ICP

Results: Raman Raman CompoundRelative Shifts (1/cm) Methyl Ethyl Ketone , , , , Ethyl Centralite , , , , , Nitrodiphenylamine , , Caliber , , , , , Caliber , , , , , Caliber , , , , , , , Shotgun (12 Gauge) , , , , , ,

Results: XRF Solid Cloth Sample (% Composition) AnalyteBariumCopperIronLeadZinc.22 caliber caliberN/A N/A.45 Caliber ShotgunN/A N/A Liquid Sample (% Composition) AnalyteBariumCopperIronLeadZinc.22 caliberN/A18.201N/A.38 caliberN/A13.936N/A.45 CaliberN/A15.754N/A ShotgunN/A7.724N/A

Results: ICP Concentration [ppm] AnalyteBariumCopperIronLeadZinc.22 caliber caliber caliber Shotgun Sample Calculation: Ex..22 Caliber/ Barium =556.28x x=19.58 ppm

ICP Calibration Curves

Discussion  Raman did not conclusively identify analytes May have needed more time to soak Could have been overwhelmed by solvent  XRF was able to detect each analyte of interest within solid method. At relatively similar distances, there seems to be no correlation between caliber size and percent composition

Discussion  XRF was only able to detect a percent composition of copper within liquid method May need to be soaked for longer to detect other analytes  ICP successfully quantified analytes of interest Generally, the.38 caliber had the highest concentration for each analyte when compared to the 3 calibers but had no correlation with the shotgun

References  Bueno, J; Sikirzhytski, V; Lednev, I. Raman Spectroscopic Analysis of Gunshot Residue Offering Great Potential for Caliber Differentiation. Analytical Chem. [Online] 2011, 1021, A-F  Lopez-Lopez, M; Delgado, J. J; Garcia-Ruiz, C. Ammunition Identification by Means of the Organic Analysis of Gunshot Residues Using Raman Spectroscopy. Analytical Chem. [Online] 2012, 1021, A-D

Special Thanks  Matt Cunningham for providing GSR samples  Dr. Foy for letting us play with really expensive instruments  Our lab assistants: Kiersten and Pat L.  Professor Mowery for ordering our chemicals Look at that center burst!