analysis of gunshot residue by x- ray fluorescence, raman spectroscopy, and inductively coupled...
TRANSCRIPT
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
Inorganic Organic
Iron Ethyl Centralite
Copper 2-Nitrodiphenylamine
Lead
Barium
Zinc
Samples
Caliber Distance
.22 < 3 feet
.38 < 3 feet
.45 < 3 feet
Shotgun: 12 gauge 4-5 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: RamanRaman
Compound Relative Shifts (1/cm)
Methyl Ethyl Ketone 2976.000, 2920.743, 1710.000, 1084.000, 759.000
Ethyl Centralite 2971.981, 3063.748, 2933.020, 705.528,428.901, 1455.783
2-Nitrodiphenylamine 1144.701, 1255.381, 204.184
.22 Caliber 2978.795, 2920.972, 2735.317, 1712.384, 1084.200, 759.522
.38 Caliber 2976.523, 2920.897, 2735.063, 1709.513, 1085.329, 759.961
.45 Caliber2978.502, 2920.782, 2737.978,
1711.065, 1083.950, 760.048, 585.511, 408.906
Shotgun (12 Gauge)2977.995, 2920.835, 2733.644,
1709.547, 1084.542, 759.548, 405. 193
Results: XRFSolid Cloth Sample (% Composition)
Analyte Barium Copper Iron Lead Zinc
.22 caliber
9.830 1.621 1.356 64.044 0.496
.38 caliber
N/A 1.836 1.739 3.269 N/A
.45 Caliber
12.990 11.337 0.553 17.053 1.644
Shotgun N/A 1.876 2.317 10.201 N/ALiquid Sample (% Composition)
Analyte Barium Copper Iron Lead Zinc
.22 caliber
N/A 18.201 N/A N/A N/A
.38 caliber
N/A 13.936 N/A N/A N/A
.45 Caliber
N/A 15.754 N/A N/A N/A
Shotgun N/A 7.724 N/A N/A N/A
Results: ICP
Concentration [ppm]
Analyte Barium Copper Iron Lead Zinc
.22 caliber
19.6 13.6 20.1 20.8 15.6
.38 caliber
1346.6 70.3 640.0 958.7 48.5
.45 caliber
856.7 59.2 516.9 654.2 28.8
Shotgun 1153.0 63.9 1023.9 1740.4 44.9Sample Calculation: Ex. .22 Caliber/ Barium8688.5=556.28x-220.9
x=19.58 ppm
ICP Calibration Curves
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!